Title Page
 Board of Control
 Table of Contents
 Introduction and Acknowledgmen...
 Injurious insects
 Scale insects
 Predacious insects
 Control by fungous parasites
 The new citrus aphid
 The melon aphid
 Borders of trunk and limb
 Leaf eaters
 Slug caterpillars
 Citrus root-weevil
 Other pests of young trees
 Allies of the citrus grower
 Other vertebrates

Title: Citrus insects and their control
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00027151/00001
 Material Information
Title: Citrus insects and their control
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 287-423 : ill. ; 23 cm.
Language: English
Creator: Watson, J. R ( Joseph Ralph ), 1874-1946
Berger, E. W ( Edward William ), b. 1869
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1926
Subject: Citrus -- Diseases and pests -- Florida   ( lcsh )
Citrus -- Diseases and pests -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by J.R. Watson ; with sections on entomogenous fungi by Dr. E.W. Berger.
General Note: Cover title.
General Note: "A revision of Bulletin 148"--T.p.
General Note: Includes index.
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00027151
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000923487
oclc - 18172753
notis - AEN4038

Table of Contents
        Historic Note
    Title Page
        Page 289
    Board of Control
        Page 290
    Table of Contents
        Page 291
        Page 292
    Introduction and Acknowledgments
        Page 293
    Injurious insects
        Page 294
    Scale insects
        Page 295
        Page 296
        Page 297
        Page 298
        Page 299
        Page 300
        Page 301
        Page 302
        Page 303
        Page 304
    Predacious insects
        Page 305
        Page 306
        Page 307
        Page 308
        Page 309
        Page 310
        Page 311
        Page 312
        Page 313
        Page 314
        Page 315
        Page 316
        Page 317
        Page 318
        Page 319
        Page 320
        Page 321
        Page 322
        Page 323
        Page 324
        Page 325
        Page 326
        Page 327
        Page 328
        Page 329
        Page 330
        Page 331
        Page 332
        Page 333
        Page 334
        Page 335
        Page 336
        Page 337
        Page 338
        Page 339
        Page 340
        Page 341
        Page 342
        Page 343
        Page 344
        Page 345
        Page 346
        Page 347
        Page 348
        Page 349
        Page 350
        Page 351
        Page 352
        Page 353
        Page 354
        Page 355
    Control by fungous parasites
        Page 356
        Page 357
        Page 358
        Page 359
        Page 360
    The new citrus aphid
        Page 361
        Page 362
        Page 363
        Page 364
        Page 365
        Page 366
        Page 367
        Page 368
        Page 369
        Page 370
        Page 371
        Page 372
        Page 373
    The melon aphid
        Page 374
        Page 375
        Page 376
        Page 377
        Page 378
        Page 379
        Page 380
        Page 381
        Page 382
        Page 383
        Page 384
        Page 385
        Page 386
        Page 387
        Page 388
        Page 389
        Page 390
        Page 391
        Page 392
        Page 393
        Page 394
        Page 395
        Page 396
        Page 397
        Page 398
    Borders of trunk and limb
        Page 399
        Page 400
        Page 401
    Leaf eaters
        Page 402
        Page 403
    Slug caterpillars
        Page 404
        Page 405
        Page 406
        Page 407
        Page 408
    Citrus root-weevil
        Page 409
        Page 410
    Other pests of young trees
        Page 411
        Page 412
        Page 413
        Page 414
        Page 415
        Page 416
    Allies of the citrus grower
        Page 417
    Other vertebrates
        Page 418
        Page 419
        Page 420
        Page 421
        Page 422
        Page 423
Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida

(A revision of Bulletin 148)

Agricultural Experiment Station




(With Sections on Entomogenous Fungi
by Dr. E. W. Berger)

bulletins will be sent free upon application to the Experiment Station,

Bulletin 183

June, 1926

P. K. YONGE, Chairman, Pensacola
E. W. LANE, Jacksonville
A. H. BLENDING, Leesburg
W. B. DAVIS, Perry
J. T. DIAMOND, Secretary, Tallahassee
J. G. KELLUM, Auditor, Tallahassee

WILMON NEWELL, D. Sc., Director
JOHN M. SCOTT. B. S., Vice Director and Animal Industrialist
SAM T. FLEMING, A. B., Assistant to Director
J. R. WATSON, A. M. Entomologist
ARCHIE N. TISSOT, M. S., Assistant Entomologist
H. E. BRATLEY, M. S. A., Asst. in Entomology
R. W. RUPEECHT, Ph. D., Chemist
R. M. BARNETTE. Ph. D., Assistant Chemist
C. E. BELL, M. S. Assistant Chemist
E. W. COWAN, A. M., Assistant Chemist
J. M. COLEMAN, B. S., Assistant Chemist
0. F. BURGER, D Sc., Plant Pathologist
G. F. WEBER, Ph. D., Associate Plant Pathologist
J. L. SEAL, M. S., Assistant Plant Pathologist
ROBERT E. NOLEN, M. S. A., Lab. Asst. in Plant Pathology
K. W. LoucKs, A. B., Lab. Asst. in Plant Pathology
ERDMAN WEST, B. S., Lab. Asst. in Plant Pathology
D. G. A. KELBERT, Field Asst. in Plant Pathology
W. E. STOKES, M. S., Agronomist
W. A. LEUKEL, Ph. D., Assistant Agronomist
A. F. CAMP, Ph. D., Associate Horticulturist
W. A. CARVER, Ph. D., Assistant Cotton Specialist
EDGAR F. GROSSMAN, M. A., Assistant Entomologist, Cotton Investigations
RAYMOND CROWN, B. S. A., Field Asst., Cotton Investigations
A. L. SHEALY, D. V. M., Veterinarian
D. A. SANDERS, D. V. M., Assistant Veterinarian
C. V. NOBLE, Ph. D., Agricultural Economist
BRUCE MCKINLEY, B. S. A., Assistant in Agricultural Economics
H. G. HAMILTON, M. S., Assistant Agricultural Economist
OUIDA DAVIS ABBOTT, Ph. D., Head, Home Economics Research
GEORGIA WESTOVER, Assistant in Home Economics
HAROLD MOWRY, Assistant Horticulturist
G. H. BLACKMON, B. S. A., Pecan Culturist
W. B. TISDALE, Ph. D., Plant Pathologist, in charge Tobacco Experiment
Station (Quincy)
J. G. KELLEY, B. S. A., Field Assistant, Everglades Expt. Station, (Belle
JESSE REEVES, Foreman Tobacco Experiment Station (Quincy)
L. O. GRATE, Ph. D., Assistant Plant Pathologist (Hastings)
A. S. RHOADS, Ph. D., Assistant Plant Pathologist (Cocoa)
A. N. BROOKS, Ph. D., Assistant Plant Pathologist (Plant City)
STACY 0. HAWKINS, Field Asst. in Plant Pathology (Miami)
J. H. JEFFERIES, Superintendent Citrus Experiment Station (Lake Alfred)
W. A. KUNTZ, A. M., Assistant Plant Pathologist (Lake Alfred)
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle Glade)
J. H. HUNTER, M. S., Assistant Agronomist, Everglades Expt. Station,
(Belle Glade)
K. H. GRAHAM, Auditor
RACHEL MCQUAmRIE, Assistant Auditor

INTRODUCTION AND ACKNOWLEDGMENTS ...-...........-... ........... ..... ..... 293
INJURIOUS INSECTS ....-----....--.....--.... .---- ----- ----------- 294
Scale-Insects .....-.....-..-- ----.--...---..--. -----................. 295
Armored scales, life history .....-............. -----...........-.. -... .-...-... --- 296
Purple scale, life history, broods, association with whiteflies,
dam age ................................ ...... -.................... ................. ....... ---- 297
Natural checks-
Entomogenous fungi ..............................-......... .........- ..... 302
Predaceous insects; ladybeetles, downy darkling beetle, lace-
wing flies or aphis lions, trash bugs, predaceous mites,
internal parasites ................................... ..................... .. .... 305
Control of purple scale -........--- ......-......-- .......--...----............ ... 310
Long scale ......--.... -- .... ................ ............------- -... ................ 312
Florida red scale or nailhead scale, life history, natural checks,
control ..........-........ .. .... .. ........... ... ........................ 313
Minor armored scales-
California red scale .........----...........................--- 315
Dictyospermum scale ..-.....-..------.................. ----- .............. ....... 316
Rufous or West Indian red scale ...............------...................---- ... 316
Camphor scale ...............----- -.. ... ... ..... ...... ................ ... ... 316
San Jose scale ........ ---------.............. ... ...................... .... .......... 316
Chaff scale, life history, natural checks, control measures, food
plants ............. ..........--- -.... ..-----....- -....-----................-....... 317
Snow scale -- ........- .. ......................... ...............- ........-.. 318
Soft 'scales, life history ........................-.....- ......... .......--.............. 319
Turtle-back or soft brown scale, life history................................. 320
Hemispherical scale ---... -----.....-............. ........-...... ........................ 321
Black scale ..... ............................................. ------ 322
Wax Scales-
Florida wax scale, natural checks, host plants, control............ 322
Barnacle scale ...................-- ---.. --..-.. ---....... ................................. 324
Japanese or Mexican wax scale .............................................-- .... 324
Pyriform scale .......................................-....... ...................... ...- 325
Green shield scale ....--- .. --... .....- ..................................................... 326
Entomogenous fungi of soft scales .............................................. 326
Mealybugs .........................................--- ...-------- .....---- ........... .----- 328
Common mealybug, life history, predators, the mealybug fun-
gus, control ................--- ...---- ...-...----- .. .............-.......- ..-.... 329
Long-tailed mealybug ...........-....... .......-........-.................. -..331
Cottony cushion-scale, appearance, life history, control, Aus-
tralian ladybeetle ...........................................................-........ 332
W hiteflies, life history ........ --... .. .--........-...- --...... --..----........ .......-. 335
Common whiterfy, life history, food plants, parasites and preda-
tors ...-----........... ................-...................... -------337
Cloudy-winged whitefly, description, life history, control..-............. 341
Woolly whitefly, description, natural control, artificial control.... 343
Minor species-
Flocculent whitefly ......................................................... .... 346
Guava whitefly ................... ..----------------------.................-- 346
Bay whitefly ........... .......... .......... ...---...... .. ---. .-- ..---. 346
Inconspicuous or sweet potato whitefly ....................... ..................... 346
Mulberry whitefly .......................-- ......--- .........--... 347
Other whiteflies .---..............................- .......... ... .. 347
Whitefly fungi, red aschersonia, yellow aschersonia, brown white-
fly-fungus, white fringe fungus, cinnamon fungus............ 347
Control of whiteflies and scale-insects.................-....... .............. 350
Spraying .---. ....--- .............................. ..................---.....-. 351
Fumigation ......-.......---.....--.--...-----. ..-..----- ..... ....--------- 354
Control by fungous parasites ------...................... .................. 356
Aphids ..-- -----..... .......................-- --....... ....................... .. 360
The new citrus aphid, life history ....................--- ------ .................... 361
Enemies ...---....-------------... --... -. --..................--...... 363
Ladybeetles .................... .................-.------- -....... 363

Blood-red ladybeetle ........ ........... ..................... 363
Convergent ladybeetle -........ ..........-............-.... .............. 364
Two-spotted ladybeetle ............. -.... ....................-..... .....-- ..- 365
Scymnus term inatus ....... .....................---- ----............................... 365
Chinese ladybeetle .......-...-.............-- ........................................- 366
Syrphus flies ---................. ...... .........---- ........................ .... 367
A phis lions ....-- .....-.....----..............- ......................... ..... ......----- ..... 368
Fungous diseases ---..---.... ---......... ------.....---.................-.................. 368
The effect of heavy rains ................-- .....-------- ..........................--. 369
Control ..................... ...... .......-- ..................................... ................... 369
The melon aphid ........ ---- ----....... .....-....----....-----------.................. 374
Rust mite, appearance, life history, natural control, control, sul-
phur the best insecticide, spraying ..................................... 374
Red spiders--- --- -------.......--..................-------------------.........--- 381
Six-spotted m ite ............................. ..... .. .. .........- ...--............ 381
Purple m ite ..----- --.--.... ....-.................-....... ...-... ...........-.......-.....-...... --382
Florida flower thrips, character and extent of damage, thrips marks
on the fruit, life history, natural control, spraying ........... 382
Large plant bugs .-.........................--......-....-----.................... .......... 387
Southern green stink bug or pumpkin bug, life history, control,
prevention ---------- ----..... -......... ..... ...-........ ---... ---.... -.....-- ... 387
Other plant bugs ......-- .......................- ..---- ........................... 393
Cotton stainer .. ----........---------........----..--................ ..........-- .- -----.. -- 394
Minor pests of the fruit-
Orange tortricids ....--....-- ....--- ...-.............-...--- ..--........ --......------... 394
Grasshoppers and katydids ..--......--............- .....-.....-...- ...... .......... 396
Bagw orm s ...............-... .................. ..... ........-- ........-- ................. ..... 396
Rodents ........... .... ..-- ..-.. ...-.. ... ........... ............ .......... .. .. ..-- ..--.- 397
Mediterranean fruit fly .........-.................-.......----...--...--........ 397
M orelos fruit fly ..--..........-......--...-......... ....... ........---- .. ........... ..--.. 398
Scavengers .-..-----..........-........ .................. -....... -....... ........... -.... ........... 398
Borers of trunk and limbs ..........................._ ...... ........ ......--... 399
Orange saw yer ................... .......- ... ....... ... -.....-..- ....... .......... 399
Shot-hole borers, or pinhead borers ..........-- ....................... ......... 399
Tineid m iner ...--..................... ........... ............ ..... ...... ....-...--- ..--.. 400
Bark and leaf scavengers-
Psocids ........ ......... --.......- ..-----...--- -----------.. --... .......-- .. .. 400
Hymenorus obscurus ............. --.. -...--.----..--...---- ....-..........-----.. --- ---401
Minor pests of young trees ..-..-..........-. ....................------.....-. 401
Leaf eaters-
Orange dog ...- -----......... -........... ........ ------ 402
Slug caterpillars-
Puss m oth ---- ---..-.. ---... -......- ...--- ..... ..... ......................... 404
Saddle-back ............................. .....................-.......-............... 404
Hag moth .......-..-- ....- ..-... ......-.~.~..... ....--------- ---...... 405
Grasshoppers ......-....... ........ ........ ...................................................... 406
Katydids ....... --...... ----------------........... .....-..-.. ...----.....--..... 408
Citrus root weevil .... ---............-.... .. ..-.... -.. ........ ... --.. 4409
June bugs ........-..--..-.................. ... ...... ..-.... ... ... ......... ..--- ... 409
Prickly ash beetle .---... ..-- ... .... ......-------..-- .. ........ ....... ....- ..---- 410
Striped cucumber beetle .. .......-- -----.. ..-- .-- .... ...... ..-..................... 410
Other pests of young trees-....-...--..-----..---.....-..--.....--.......-- ......... 411
Sharp-shooter or orange jassid ............. .............- .....-- .... ...-.......- ... 411
Ants, on budded trees, keep ants off trees, as protectors and car-
riers of scale-insects, control ....................... .......---- ...... 412
White ants, termites, or wood lice---............................ -----. --- 414
"Salamanders" and "gophers" ..................~..............------........ .. 415
Ground squirrel, pocket gophers or "salamanders" ........ .......... 415
The burrowing turtle .---.............----..----........-........... .. .. 416
M illipeds ......................... ............ .............. .... .... ..... ....... 416
ALLIES OF THE CITRUS GROWER ..----...... --........-----... ...................... 417
Birds ....----- ..... ............---------- -....... .. ....... ...-........... 417
Other vertebrates ......... ...... .. ... .. ............ ..--- ..-----...- ...... .. 418
Predaceous bugs ...-----...... ......---------... ...............---..................... 418
W asps ............................ -- ............ ...... .........---- ........... .........---- 418
Parasitic flies ... --....... -- -.. -----.....----...........- ...... ..... ............ .. 419
TREES THAT HARBOR CITRUS INSECTS .... ........................ .......-.......- 419

The aim of this bulletin is to discuss briefly the most common
insects in the Florida citrus grove-the beneficial insects and
those of an indifferent relation, as well as those which injure
the tree-so that the grower may be enabled to recognize the
more common insects in his grove. No attempt has been made
to treat in full all insects to be found on an orange tree.
The writer has selected chiefly those insects which have been the
source of much correspondence with citrus growers. Neither
has an attempt been made to present an exhaustive account of
the more important pests, nor to repeat data that are easily
accessible to the average grower thru other publications. How-
ever, an occasional reference to such literature is included so
that the grower may readily find further detailed information.
In addition to the insects, red spiders, rust mites and other mites,
and other animal pests troublesome to citrus growers are in-
cluded in the discussions.
For studying the smaller forms and the early stages of a
majority of the insects, a good hand lens is necessary. A satis-
factory one, magnifying fifteen or sixteen diameters, can be
bought for three or four dollars. A glass of less power would
hardly be sufficient for the study of rust mites and many of the
eggs while a lens of higher power would present a field too small
to enable the observer to find again readily an object first located
with the unaided eye.
All of the photographs used in preparing the illustrations for
this bulletin not otherwise credited were made by the assistants
in the Department of Entomology of this Station,-Messrs. U.
C. Loftin, A. C. Mason, H. L. Dozier, A. H. Beyer, and A. N.
Tissot. Mr. Dozier made the drawings of the Australian lady-
beetle and the downy darkling beetle. The drawings in the sec-
tion on aphids were made by Mr. Ralph L. Miller of the State
Plant Board, who since January, 1926, has been in charge of
the entomological investigations carried on at the Citrus Sub-
station at Lake Alfred. To Mr. W. L. Thompson, of the same
organization, is due credit for all the detailed life history work
on the ladybeetles here given. The life history work on the new
citrus aphid has been carried on by Mr. A. H. Beyer and Mr.
A. N. Tissot, Assistant Entomologists of the Experiment Station.
The sections on the entomogenous fungi were written by Dr.

Florida Agricultural Experiment Station

E. W. Berger, Entomologist of the State Plant Board. To Dr.
Berger and Mr. G. B. Merrill, of the State Plant Board, the
writer is indebted for valuable suggestions especially in the sec-
tion on scale-insects and to Mr. W. W. Others for reading and
criticizing the section on spraying for whitefly and scale-insects.
Some illustrations have been taken from previous publica-
tions by this Station. The Bureau of Entomology, U. S. D. A.,
has supplied the photographs from which other cuts were made.
The California Experiment Station has loaned one illustration,
and Florida State Plant Board nine. These are duly credited
where used.
Of the insects and mites treated in this bulletin there are but
six which should be classed as pests of primary importance,
against which the grower who would produce the maximum
amount of first-class fruit will find it necessary to use control
measures nearly every year. They are, in the order of their
(1) Purple scale
(2) Common citrus whitefly
(3) Rust mite
(4) The citrus aphid
(5) Florida red scale
(6) Cloudy-winged whitefly
There is a larger number of insects which should be watched,
and against which the grower should take measures during oc-
casional years. They are, again approximately in the order of
their importance:
(7) Red spiders
(8) Thrips
(9) Long scale
(10) Mealybugs
(11) Cottony cushion-scale
(12) Citrus snow scale
(13) Orange dog
(14) Chaff Scale
(15) Pumpkin bugs and other plant bugs
(16) Termites
(17) Ants
(18) Gophers and salamanders


Bulletin 183, Insects of a Citrus Grove

In a third class may be placed those whose activities are harm-
ful, but which seldom become sufficiently abundant to make it
worth the grower's while to combat them. Such are:
Grasshoppers Florida Wax Scale
Katydids Barnacle Scale
Sharpshooters Inconspicuous Whitefly
Orange Tortrix Bay Whitefly
In addition to the foregoing insects which directly damage the
trees, there are many insects which damage the grove indirectly
either by giving aid and comfort to its enemies, as ants which
protect mealybugs, or by destroying beneficial insects, as do
certain parasites that live in ladybeetle larvae.


The most serious insect pests of citrus in Florida are scale-
insects. They derive this name because of the fact that they
are usually flat and are closely applied to the surface of the
host plant like a scale. They are bugs and, therefore, sucking
insects, although very degenerate in structure. While most in-
sects go thru four stages during their development (egg,
larva, pupa and adult) this is true of only the males of scale-
insects. The females virtually omit the last two stages. They
acquire mature sexual organs and reproduce while still retain-
ing the larval form. Even in the male the adult life is extreme-
ly brief, lasting for but a day or two. As the adult males are
very small and inconspicuous, gnat-like creatures, the orange
grower seldom notices them. They have only two wings. Hav-
ing no mouth parts or digestive organs, they can take no food
during their adult life. Their only activities consist in finding
and fertilizing the females.
The scale-insects damage the trees chiefly by the withdrawal
of large quantities of sap. They also give off a sweet secretion
called honeydew and in this honeydew a fungus known as sooty
mold develops. Mealybugs and some of the soft scales, like the
turtle-back scale, produce this honeydew copiously.
Three Kinds of Scale-Insects:-The family of scale-insects
(Coccidae) may be divided into three groups, or sub-families,
according to the nature of the scale or covering of the insect.
In the first group the larva secretes two plates of a hard,


Florida Agricultural Experiment Station

horny substance between which the insect lives, much as an
oyster in its shell, altho not attached to the plates by muscles.
The lower plate next to the host plant is usually thin, delicate
and flat, but the upper one is more or less arched, thick and
rigid. The newly-hatched larva moves about for a few hours,
but at the end of one or two days inserts its beak into the host
and becomes anchored for life. Its beak, after being inserted
into the tissue of the host, grows extensively so that the insect
cannot withdraw it. If an attempt is made to pull it out by
force it usually breaks off; if successfully extracted it cannot
be reinserted. Insects of this group are called armored scales
(Diaspinae) .
In the second group no separate detached scale is formed, but
the body wall itself is usually thickened and hardened by the
deposition of horny chitinous material. The scale in this case
is part of the animal like the "shell" of a turtle. In this group
the larva can usually move about until egg laying time, but it
moves very slowly. Insects of this group are called soft scales
In the third group, mealybugs and their relatives (Dactylo-
pinae), no hard coating is formed but the body is usually cov-
ered with flaked wax which gives a mealy appearance. They
retain their legs and are capable of moving about thruout life.

Armored Scales
In the armored scale group the eggs are laid under the scale
of the female whose body contracts as they are laid. Shortly
after the last one is laid the shriveled female dies. The eggs
hatch under this protective covering which shelters them not
only from rain and cold but also from other insects which might
otherwise feed upon or parasitize them. It also protects them
from insecticides. Soon after hatching, the young, called
"crawlers", push their way out and wander about for a few
hours seeking a satisfactory place to attach themselves. Hav-
ing found it, they insert their beaks composed of four slender
threads, and, if they are destined to become females, never
move again. They at once begin to secrete threads of wax
which form a covering over the body. In two or three weeks
they have outgrown their larval skins and must molt. After
this molt the true permanent scale begins to form. Some weeks


Bulletin 183, Insects of a Citrus Grove

later a second molt takes place. This time, however, the molted
skin is retained and incorporated with the new portion of the
scale where it is usually quite conspicuous. (Fig. 132.) It is
situated in the middle or near the front end of the mature scale
and often differs a little in color from the remainder. At this
point in the life history a difference between the males and fe-
males begins to be noticeable. The males grow no more but
molt again and pass into the pupal stage from which the adult
two-winged fly-like creatures emerge in about a week.
The female is fertilized
shortly after the second molt
and does not molt again, al-
tho she continues to increase
in size. As a result of this
growth after the second molt,
the female scales are much
larger than the males and
live longer. The males go A B
Fig. 132A.-Scale of female with exuviae
thru this molt at an age ear- central: a, first exuvia; b. second exuvia:
c, secretionary covering. B.-Scale of female
her by about a week than the with exuviae terminal: d, first exuvia; e, sec-
ond exuvia; f, secretionary covering. (From
females. The third and fourth Quart. Bull. State Plant Board, Vol. VII,
molts are then passed quick- No. 4)
ly, so that by the time the females are thru with their second
molt and are ready to breed, the males have become winged
adults and quickly find the females. The armored scales pro-
duce very little honewdew.

Lepidosaphes beckii (Newm.)
The purple scale is the most destructive insect in Florida
citrus groves. The mature scale (Figs. 133 and 134) is shaped
somewhat like an oyster shell. It is purplish-brown in color
and 1/8 inch in length. It is found on the twigs and fruit as
well as on the leaves. However, it is not abundant on the trunk
or larger branches except on young trees. On the leaves it col-
lects especially along the midribs and at the base, but occurs
on any part, on the upper as well as the lower surface.
Like whiteflies and all other bugs, scale-insects are sucking
insects and withdraw large quantities of sap from the trees.
Altho the effect of scattered individuals is not externally ap-


Florida Agricultural Experiment Station

parent, they check the growth of the infested part and inter-
fere with its functions. If sufficiently abundant in one place
they will cause that portion of the leaf to turn yellow, and if
they continue to multiply the leaf will fall. These yellow spots
will often persist after the scales have been killed by natural
causes or by sprays and have fallen off. A heavily infested fruit
is small and slow to color.

Fig. 133.-Purple scale on grapefruit, showing reaction to light. The clear spot in the
center was in contact with another fruit

Besides this direct injury the punctures of scale-insects af-
ford avenues of entry for certain fungous diseases of the fruit,
such as stem-end rot.
The eggs are laid under the scale of the mature female. They
hatch in from fifteen to twenty days. The young crawlers re-


Bulletin 183, Insects of a Citrus Grove

main under the shelter of the parent scale for a day or two and
then spend another day or two in crawling about looking for a
suitable place in which to affix themselves. These crawlers
show an aversion to strong light. If a crawler is placed on a
sheet of paper a part of which is in the sunlight, the insect will
not usually crawl into the sunny part from the shade, but will
either turn back upon reaching it or crawl along the edge of the
shadow. On the other hand, if placed in a room near a window,
but not in direct sunlight, the insect will travel toward the win-
dow. The crawlers avoid both deep shade and direct sunlight

Fig. 134.-Purple scale following woolly whitefly. (From Bul. 123.)

and seek an intermediate condition. If placed on a twig in total
darkness they will crawl to the top. Because of these reactions
to light the crawlers collect in shaded places, a favorite place
being under the calyx of the fruit. Two fruits touching or a
leaf resting against a fruit also produce conditions of shade
favorable to the insect. (Fig. 133.) Sooty mold slightly loose
so that the crawlers can get under it, forms favorable retreats,
as does also the wool of the woolly whitefly. (Fig. 134.) Prob-
ably for this reason scale-insects are usually more severe along
a road than in other parts of the grove. The dust particles
settling on the leaves provide the crawlers with the partial
shade and protection which is most favorable for their develop-
ment. An unusually favorable place for the development of the
scale crawlers is in the leaves curled by the new citrus aphid.
These curled leaves seem to supply the optimum degree of light


Florida Agricultural Experiment Station

to the crawlers. The result is a heavy infestation of scales in
these curled leaves where they are very difficult to reach with
a spray solution.
The crawlers also have a definite reaction to gravity. In the
dark they will always climb up a branch-a reaction called neg-
ative geotropism, a movement opposite to the pull of the earth.
This leads the crawlers toward the tops of the branches where
they find suitable food. Their reactions to light, however, are
much stronger than those to gravity so that when the two come
into conflict the aversion to light will prevail.
Immediately after affixing themselves the young scales begin
to secrete waxy threads which soon thinly cover the body. When
about eighteen or twenty days old, in summer, the first molt
occurs and immediately afterward the insect begins to form the
true scale, which is reddish- or purplish-brown in color.
When the female is six or seven weeks old, in summer, the
second molt occurs. The scale covering the second-stage larva
is incorporated with the new scale; a habit characteristic of all
armored scales. In the purple scale most of the new material
is added on one side of the first scale which therefore comes to
occupy a position near the apex of the mature scale. (Fig.
132B.) The female begins to lay eggs when about two months
old and continues to lay for three or four weeks, averaging
thirty or forty eggs.
The entire life history extends over a period of about three
months, in summer. During cooler weather the growth and
development takes place much more slowly, altho in our climate
probably seldom wholly ceases.

All stages may be found in one tree at almost any time of the
year, yet there are three periods when crawlers are more abund-
ant than at other times. They are in March or early April,
June or July, and September or October. Thus there are in the
main, three generations a year.
It has been commonly noted that a heavy infestation of white-
flies is likely to be followed by a marked increase in the amount
of purple scale present in a grove. Divers explanations have
been given to account for their association, a common one being
the weakened condition of the trees. While it is undoubtedly


Bulletin 183, Insects of a Citrus Grove

true that a weakened tree cannot endure the attacks of as many
scales as a vigorous one, the weakened condition of the tree
obviously cannot be the cause of the multiplication of the scales.
The true explanation is to be found in the protection given to
crawlers and young scales by the sooty mold. As previously
stated the crawlers' aversion to strong light drives them to seek
the protection of sooty mold. When the mold is first formed it
adheres so closely to the leaf that the crawlers cannot get under
it; but in time it becomes sufficiently loosened to afford them a
retreat. Also, the sooty mold may form over the larvae after
they have anchored. The sooty mold partly protects the crawlers
and young larvae from some of their predators and parasites,
both insects and fungi. Extensive tabulations by the writer
have shown that the percentage of infestations with the para-
sitic fungi is less under the sooty mold than where the scales are
fully exposed.
In the case of the woolly whitefly, in addition to the sooty
mold, the wool itself and the honeydew with which it is usu-
ally entangled form an ideal refuge for the scales and an old
colony of this whitefly almost invariably shows a heavy infes-
tation of purple scale.* (Fig. 134.)

How seriously the purple scale damages trees by sucking the
sap is shown most clearly when the scales collect in groups on
a leaf, as under a colony of woolly whitefly. The part of the leaf
attacked turns yellow while the other parts remain green.
These yellow areas often persist after the scales have matured
and fallen off. These spots may turn brown and finally become
holes in the leaf or they may be infected by fungi or become
the seat of gum exudations; some of the smooth, shining dark-
brown spots on leaves, commonly called "greasy spots" or
"black melanose," have their origin in attacks of scale insects.
If too large an area of the leaf is attacked by scales the leaf
will fall.
The attacks of the scale on the twigs are attended by as seri-
ous consequences as on the leaves, a heavy infestation resulting
in the death of the twig.
On the fruit the results of the activities of scales are hardly
less marked. If the scales are abundant, the fruit is stunted,

*For further details see Fla. Ag. Exp. Sta. Bul. 126.


Florida Agricultural Experiment Station

ripening is delayed and the coloring is uneven. Vigorous scrub-
bing is necessary, to remove the scales before packing the fruit.
Another serious consequence of the presence of scales on fruit
is that the punctures made'in the rind afford avenues for the
entry of various fungi which cause decay, as previously stated.
The efforts of the crawlers to avoid strong light cause them to
collect under and around the calyx of the fruit. If scales are at
all abundant on the trees, there will always be found a heavy
infestation about and under the calyx, and often the entire
spacp is covered with a layer of scales several deep. Fawcett
has shown (Fla. Ag. Exp. Sta. Press Bul. 195) that there is an
intimate relation between the numbers of scales in this situation
and the development of stem-end rot in the fruit.

(By E. W. Berger)
:The most efficient parasites of the purple scale are entomog-
enous fungi. There are five species that are especially common
on this scale. Named in the order of their abundance they are
the red-headed scale-fungus, the white-headed scale-fungus, the
black scale-fungus, the pink scale-fungus and the cinnamon fun-
gus. (See page 350.) As in the case of those species which para-
sitize the whiteflies, these fungi grow most abundantly during
the rainy season. Their development is not, however, so strict-
ly limited to the summer season as is that of the whitefly-in-
festing species. They often grow well and do efficient work
even in mid-winter but only during a period of considerable
humidity and warmth. They do not thrive well during a very
dry season.
PINK SCALE-FUNGUS.-(Nectria diploa B. & C.)** This fun-
gus was discovered by Professor P. H. Rolfs at Winter Haven,
Florida, in December, 1912. It has since been found widely
distributed in Florida (and other countries) but not so gen-
erally, nor is it so common as the red-headed scale-fungus. To
the casual observer it is indistinguishable from the latter
fungus and Fig. 135 will serve here as an illustration of
*The scientific names of the fungi as revised by T. Petch and as given
by H. S. Fawcett in his book (1926) or per letter to the writer have been
adopted in the text. The old names are given in footnotes.
**Microcera fugikuroi Miy. et Sa.


Bulletin 183, Insects of a Citrus Grove

it. The color of its heads, however, is pink rather than red,
and a pink or reddish border surrounds the scales it has killed.
It is especially effective on the Florida red scale. It has un-
doubtedly been present a long time in Florida and confused
with the red-headed scale-fungus. It has been found infecting
and killing the following scale-insects in Florida: Florida red
scale (Chrysomphalus aonidum), mainly on citrus; water oak
scale (Chrysomphalus obscurus), on water oak; red maple
scale (Chrysomphalus tenebricosus), on
red or swamp map e; California red
scale (Chrysomphalus aurantii), on citrus;
purple s c a e (Lepidosaphes beckii), on
gus (Sphaerostilbe aurantiicola (B. et
Br.) Petch) is very effective against a
number of scale-insects and is widely dis-
tributed and common. Its reddish heads,
smaller than pinheads, grow out from the
infected scales and are easily visible. (Fig.
The following scale-insects have been
found infected by this fungus in Florida:
Purple scale (Lepidosaphes beckii), on cit- Fig. 135.-Red-headed scale-
fungus o n purple scale
rus; San Jose scale (Aspidiotus pernici- (on orange). he white
in the illustration is the
osus), mainly on trifoliate orange, peach, red color o the fune
Enlarged twice. (State
plum and pear; long scale (Lepidosaphes Plant Board.)
gloverii), on citrus; ivy scale (Aspidiotus hederae), mainly on
Chinaberry; chaff scale (Parlatoria pergandii), mainly on citrus.
According to records of the Entomological Department, State
Plant Board, and others, this fungus also parasitizes the Florida
red scale (Chrysomphalus aonidum), California red scale
(Chrysomphalus aurantii), and dictyospermum scale (Chrysom-
phalus dictyospermi), all pests of citrus as well as some
other plants; Putnam's scale (Aspidiotus ancylus) on pecan;
latania scale (Aspidiotus lataniae), on Chinaberry, avocado,
loquat, etc.; palmetto scale (Comstockiella sabalis), mainly on
palmetto; lesser snow scale (Hemichionaspis minor), mainly
on hibiscus and Chinaberry; black thread scale (Ischnaspis
longirostris), mainly on palms; Parlatoria proteus, mainly on
*Sphaerostilbe coccophila Gul.


Florida Agricultural Experiment Station

palms; pine scale (Chionaspis pinifoliae heterophylae), on pines.
Sthe gray-headed scale-fungus *(Podonectria
coccicola (E. et E.) Petch) Figs. 136 and
V 137). It is apparently the first scale-fungus of
which we have any record in Florida and is
figured and described as a "Bark Fungus" by
H. G. Hubbard.**
Hubbard, however, failed to discover the
parasitic nature of this fungus and believed it
lived on dead scales. The writer believes, fur-
thermore, that it was this fungus which saved
the citrus industry in the thirties of the last
century, when the long scale had been intro-
duced at Mandarin and St. Augustine, and the
trees were killed back each year. It is re-
ported that even whiskey and aloes were tried
Fi.ead 6. Whic e but were useless in destroying the scale and
Imperfects tg reviving the trees. But after some years the
Natural size.
(state Plant trees recovered, from some unknown cause, and
Board.) there can be no doubt but that the cause was
a" fungus, wholly, or in part at least. Con-
tributing causes may have been insect ene-
mies of the scales, but as the insect enemies
now present are never so efficient, the pre-
sumption is that it was fungus. '
This fungus occurs nearly everywhere in
Florida, wherever there is the long scale or
purple scale. It is an open question whether
this fungus or the red-headed scale-fungus is
the most common. As its name indicates, it
appears as small whitish heads growing out i .
from the scales and but for its color would I
often pass for the last named fungus.
It has been found infecting and destroying
the following scales: Long scale (Lepido-
saphes gloverii), on citrus; purple scale (Lep-
idosaphes beckii), on citrus; chaff scale (Par- "Fieaded 37c -ite-f
latoria pergandii), on citrus. gus. Perfect state.
Enlarged twice.
____ (State Plant
*Ophionectria coccicola. Board.)
**Insects Affecting the Orange, U. S. D. A., 1885.


Bulletin 183, Insects of a Citrus Grove

BLACK SCALE-FUNGUS.-This fungus (Mll' ria .-m tii duriae
Mont.) is illustrated in Fig. 138. Its distribution is apparently
more northerly than the other fungi, the red-headed scale-fun-
- ggus excepted. Specimens on San Jose scale
have just been received from Virginia. It
probably occurs everywhere in Florida. It has
the appearance of black spatter or black spots.
The insects killed by it are the following:
Purple scale (Lepidosaphes beckii), on citrus;
long scale (Lepidosaphes gloverii), on citrus;
chaff scale (Parlatoria pergandii), on citrus;
San Jose scale (Aspidiotus perniciosus), main-
ly on trifoliata, peach, plum, pear; Putnam's
scale (Aspidiotus ancylus), mainly on pecan.
CINNAMON FUNGUS.-This (Verticillium he-
terocladum Penz) occasionally infects purple
scale, long scale, chaff scale, soft brown scale,
Fig. 138.-Black as well as whitefly larvae. (See page 350.)
scale-fungus. Im-
perfect stag e.
fungus areas like
la atukr apatt The purple scale is extensively preyed upon
BSrate Plant by other insects. These predators are native
insects that before the introduction of the pur-
ple scale into Florida fed upon native scale-insects. They have
gradually acquired a taste for the purple scale.
Probably the most efficient predators which feed on scale-
insects are the ladybeetles. Of these the twice-stabbed lady-
beetle (Chiloco-

Muls.) (F i g. r*
139) is by far
the most im-
portant. It is
very common
in citrus groves
where it feeds Fig. 139. The twice-stabbed ladybeetle. Larva on left. upsa in
center, and adult on right.
largely upon
the crawlers, and often on the young scales and eggs. It tears
up the females to get them. Like most of the ladybeetles this
one is nearly round in outline, almost hemispherical in shape.


Florida Agricultural Experiment Station

It is shining coal-black in color with a large red spot on each
wing case, as if it had been stabbed and blood had oozed out;
hence its name. It is about a fifth of an inch in diameter.
The young, like the larvae of all beetles, is an entirely different
looking creature from the adult. It is flattened in profile, broadly
oval in outline with the broader end in front. Like the larvae
of many ladybeetles (fig. 139) it is covered with spines. These
are black and compound; that is, the spines themselves are
covered with smaller spines. The body of the larva is bluish-
black. When ready to pupate, several of the
larvae often climb onto a dead twig and at-
tach themselves in a cluster to it. (Fig. 140.)
Ladybeetles do not crawl out of the larval skin
when they pupate but the skin splits length-
wise of the back, exposing the pupa within.
The life history of the beetle occupies about
a month.
Another ladybeetle (Exochomus margini-
pennis children Muls.), about an eighth of an
inch long is occasionally found in citrus trees
feeding chiefly on scale-insects, altho it has
been seen eating whitefly larvae and aphids.
The wing cases are brown with two comma-
g shaped black dots near the tips. The head and
Fig. 140.- Pupal
cases of the twice- thorax and the abdomen beneath are black.
stabbed ladybeetle.
Slightly enlarged. The larva is black and white. The original
habitat of this species is mostly oak trees where it feeds on na-
tive scales and aphids.
The two-spotted ladybeetle (Olla abdominalis var. sobrina
Csy.) (Fig. 177) is very similar in appearance to the twice-
stabbed and has about the same habits.
The blood-red ladybeetle (Fig. 175) and the convergent lady-
beetle (Fig. 176) also feed on scale-insects. However, their
preference is for aphids and they will be described under that
Epitragodes tomentosus (Lee.)
The downy darkling beetle (Fig. 141), a brown, oval beetle
which is about five-sixteenths of an inch long, is common in cit-
rus trees. Altho not at all related to ladybeetles it, like them,
feeds largely on scale crawlers. It is very beneficial in control-


Bulletin 183, Insects of a Citrus Grove

ling scale-insects as it feeds largely on the younger stages. Its
body is covered with very short gray hairs, hence the name.
Hubbard states that mulching the trees with
oak leaves will attract these insects to a grove.


The larvae of lacewing flies are among the
important checks to the increase of scale-in-
sects and aphids. They are flat, spindle-shaped
larvae, grayish in color but marked with brown
Figde 41E. e tsra or dull red. The front of the body ends in two
iuec. turalF sou long slender sickle-shaped jaws on which the
Hbard.)' from insect impales its victims while it sucks their
body fluids. This is done thru a tube formed
by the secondary jaw maxillaee) fitting over a groove in the
true jaws (mandibles). These larvae are voracious, attacking
insects much larger than themselves. Indeed, they do not hesi-
tate to jab their jaws into the skin on the neck or the back of
the hand of a person who happens to brush them off a tree as he
passes. The bite, while quite sharp and momentarily slightly
painful, is not seri-
ous. These larvae
are particularly
fond of aphids, and
therefore are called
aphis-lions. When
full grown, t w o
weeks or sixteen
days after hatch-
ing, they seek some
sheltered place such
as a curled leaf and
Fig. 142.-Lace-wing: Empty cocoons. Four times
spin spherical glist- natural size.
ening white cocoons about themselves. (Fig. 142.) Here they
remain for a week or ten days and then the perfect insect
emerges. Mr. R. L. Miller has five species of aphis-lions feed-
ing on scale crawlers and aphids. The adults of some (Chry-
sopa sp.) are green. The adults of the others are brown (Hem-
erobius sp.).


Florida Agricultural Experiment Station

One may often see an animated rubbish heap moving over the
surface of a leaf or the bark of a citrus tree. A close examina-
tion will reveal, projecting from the front end, a pair of jaws
similar to those of the aphis-lion. If the trash is removed one
finds a larva of an aphis-lion, but shorter and wider than most
of them. The trash is largely a collection of scalps; that is, the
dry skins of the victims of the larva.
There are two genera of lacewings common in citrus groves.
The adults of one genus are green (Chrysopa), those of the
other brown (Hemerobius). In both genera there are species
whose larvae are trash bugs and other species which do not
have the trash bug habit when young.
The aphis-lions are parasitized by minute wasp-like insects,
chalcids and ichneumons. These lay their eggs in the aphis-lions
and the grubs feed on the fatty tissues of the host. The aphis-
lion still has sufficient strength to spin its cocoon, but instead
of the lacewing the wasp-like parasites emerge. The larvae are
also parasitized by fungi and bacteria
which produce fatal diseases.
(Chrysopa sp.)
The golden-eyed lacewing (Fig. 143.)
is a deep iridescent green with eyes that
shine like drops of liquid gold. The four
delicate gauzy wings when not in use are
held up over the body like a roof. The
Fig. 143.-Golden-eyed lace- insect measures about 11/4 inches across
wing. Twice natural size. the expanded wings.
The eggs are laid on top of stiff stalks a half-inch long which
are placed in groups. These miniature forests are a common
sight on citrus leaves. This arrangement protects the eggs from
the greedy aphis-lions that will eat the eggs if they find them.
After hatching and crawling down its own stalk the larva is
not apt to find its way up another.

If a colony of scale-insects be observed under a hand lens one
will find many minute, soft-bodied 8-legged animals running
about among them. These are mites. They belong to the spider
class of animals rather than to the insects, as shown by their


Bulletin 183, Insects of a Citrus Grove

eight legs. Insects never have more than six true legs altho
many larvae such as caterpillars may have a number of fleshy
protuberances which act as legs. There are several kinds of
these mites. One of the most common is usually a pale flesh-
color but varies from white to yellow. Another is dark red.
Many of these mites feed largely or entirely on the dry ma-
terial of dead scales. Others attack living scales altho probably
none of them are able to get at the growing insect under a healthy
permanent scale covering; but they devour the first-stage young
before the permanent scale is formed. As the scale-insects reach
maturity and a large number of eggs are laid, the scale is apt to
become loosened, allowing the mites to enter and destroy the eggs.
After spraying, the scales become loosened and the mites are
able to get at the dead, dying, or injured scales. Their numbers
always increase greatly after spraying. The oil sprays undoubt-
edly kill all mites hit by the spray, but a great many will be found
untouched under dead scales or in other sheltered places.

Upon close examination of a group of scales it will usually be
found that a certain proportion of them have a round, smooth-
cut hole in the top. These scales have been parasitized and the
round hole was cut by the adult parasite as it emerged from the
dead scale. These parasites are minute four-winged creatures
belonging to the same order of insects as the wasps. They are
often spoken of as "wasp-like insects" and frequently as "wasps"
altho they are much smaller than the true wasps and belong to
different families. There are several families of these wasp-
like parasites.
In one family, the ichneumon flies, the body is usually quite
slender and wasp-like and the female is provided with long, stiff,
bristle-like appendages which project behind. These make up
the egg-laying organ or ovipositor and are sometimes many times
longer than the remainder of the insect.
In another family, Chalcids, the insects are generally smaller,
relatively short and thick, and have a shorter ovipositor than the
ichneumon flies.
The general habits of these families of insects are similar
and one account will do for all. The female lays one or more
eggs on the body of the scale-insects or in the scale's eggs either
by inserting her ovipositor under the scale or boring directly
thru it. This egg hatches into a soft, whitish, footless, grub,


Florida Agricultural Experiment Station

resembling that of a bee or wasp. The grub feeds at first on
only the body fluids or fatty portions of the host, avoiding the
vital organs. But finally the scale-insect is killed either as a
result of starvation due to the loss of its fat and body fluids, of
a direct attack on its vital organs, or of a poisoning by the larva.
The parasite after completing its growth goes into the pupal
stage and after a time makes its escape as a winged insect.
These internal parasites are an important check to the multi-
plication of scale-insects. There are many different species.
Most of them seem to be more common in winter than in sum-
mer, thus supplementing effectively the parasitic fungi.

Ordinarily the control of purple scale and of whiteflies is but
a single problem and can be better discussed after we have
studied the life histories of the whiteflies.
In case of severe infestation it may be necessary to spray twice
in order to effect a control. An interval of a month in summer
or six weeks in winter should elapse between sprayings. This
will give all the eggs which, under the protection of the mature
females, escaped the first application, time to hatch; but it will
not give them time to mature and in turn lay eggs.
There are a few special cases where the measures which suffice
to control the whiteflies may not satisfactorily control the purple
scale. As examples of such conditions may be mentioned: (1)
During the first year following the setting of the trees; (2) when
a fungicide is used on the trees; (3) when there is little or no
whitefly in the grove; and (4) following a severe infestation of
the woolly whitefly or the citrus aphid.
In a nursery row where the trees are set close together and
shade each other to a considerable extent, the entomogenous
fungi find sufficient humidity to multiply fairly well altho not as
rapidly as in a grove of large trees. When these nursery trees
are transplanted into an open field and placed many feet apart
they are fully exposed to the drying effect of sun and wind and
the fungi do not thrive. As a result the scales are apt to mul-
tiply rapidly. When nursery trees are transplanted into the
grove they should be defoliated and thoroly scrubbed with a
strong soap solution. The State Plant Board requires this in the
case of trees sold by nurseries or moved from one property to
another. It should be done to all trees when transplanted into


Bulletin 183, Insects of a Citrus Grove

the grove as it is very important that such trees be freed of
scale-insects. Young trees should be closely watched for scales
for a year or two. It will probably be found advantageous
to spray them at least three times a year. July will usually
be a desirable period in which to make the additional application.
When trees are sprayed with a fungicide to control either scab
or melanose fungi, the entomogenous fungi are also killed
and as a result the scales increase vastly (Fig. 144). Indeed it

Fig. 144.-Increase of purple scale due to spraying the tree with bordeaux mixture: Top
row, sprayed fruit; bottom row, unsprayed fruit.

is possible to kill a citrus tree in the course of a year or so by
repeated sprayings with bordeaux. Such experiences afford the
most convincing proof of the importance of the entomogenous
fungi in controlling scale-insects. The application of bordeaux
to a tree should always be followed within two months by an ap-



Florida Agricultural Experiment Station

plication of one of the oil emulsions, in order to forestall the in-
crease of the scales. At the beginning of the.rainy season the en-
tomogenous fungi should be reintro-
In groves free from whitefly,
spraying for purple scale should be
done immediately following the time
when crawlers are most abundant,
which is about the middle of April.
mid July, late October, and the
middle of February if the weather
h as been warm. The more important
of these dates correspond quite close-
,< ly with those which are preferable
for spraying to control whitefly. But,
as explained under; -whitefly, the
April spraying,, should bepostponed
until the fruit is an inch in diameter.
This may defer the application until
Lepidosaphes :, eirl (Pack.)
Mixed with the purpil'sgales may
often be found other scq whichh are
Almost identical in color and of.about
the.same length, but straighter and
much narrower. These are the long
scales. (Fig. 145.) They are close-
ly related to the purple scale to which
they bear such a marked resemblance
I that growers do not ordinarily dis-
tinguish between them.
According to Ashmead ("Orange
Fig. 145.-Long scale (Lepin,- Insects") this scale was introduced
rsaPhe. loveii). Twice natu- into Florida about 1835 at Mandarin.
By 1860, it had spread over the orange districts and had become
so destructive that it threatened the existence of the citrus in-
dustry. Glover, in 1857, stated that it was entirely free of para-
sites. This accounts for its rapid multiplication. Later, para-
sites, both insects and fungi, appeared and were finally able to


Bulletin 183, Insects of a Citrus Grove

control it better. Some of these parasites were probably intro-
duced from the original home of the scale, thought to be southern
China, and native insects gradually developed a taste for the
long scale. As late as 1885 it was, according to Hubbard, much
more common than the purple scale, altho now it is much less
Its life history, parasites and control are practically identical
with those of the purple scale. It is a little more closely con-
fined to the twigs and branches and less to the leaves and fruit
than the purple scale.

Chrysomphalus aonidum (L.)
Scale for scale the Florida red scale is the most pernicious of
our citrus scale-insects. It does not do as much aggregate
damage as the purple scale because it is not as common, but
when it does become abundant it almost defoliates a tree. It
is less common in the northern part of
the citrus belt, probably because it is
almost entirely confined to the leaves
and fruit and when these are removed
by a freeze it is almost exterminated.
This scale is dark reddish-brown in
color, with a conspicuous light brown
center, almost circular in outline (fig.
146), and about a twelfth of an inch
in diameter when full-grown. The
lighter colored center is formed by the
cast-off first larval skin or scale. This
is nipple-shaped and varies in color from
grayish to a reddish-yellow brassy Fig. 146.-Florida r e d scale
color. The surrounding part of the Chsow, Ihalus .onidum. (L.)
scale, that which covers the second lar-
val skin, is light reddish-brown, but a little darker than the
first larval skin. The scale of this insect is very thick and heavy,
much more so than that of the purple scale.
The mature female under the scale is bright yellow in coloi
and the shape of a wide short top.
The scale of the male is only about one fourth as wide as


Florida Agricultural Experiment Station

that of the full-grown female and a little lighter in color. On
one side, the posterior, there is a grayish lobe. Its position and
appearance gives the impression, at a superficial glance, of
a liquid which has been pressed out from under the scale and
then hardened. The presence of this lobe serves to distinguish
readily a male from a young female.
The eggs are yellow in color and the young crawlers bright
yellow, the color of the mature female.
This scale seems to have been first noticed in Florida at Or-
lando in 1879 on a sour orange tree brought from Cuba in 1874.
The males complete their growth in about seven weeks, in
summer. The crawlers are at first oval in form. They begin
to form their scales when less than a day old. By the second
day they cease to crawl and by the third day the scale has become
nearly circular in outline. The first molt occurs at the age of
about three weeks. The males complete their growth in about
seven weeks and soon afterward the females are fertilized.
Young are born when the females are about ten weeks old and
continue for several weeks.
The larvae, and especially the crawlers, are preyed upon by
ladybeetles and aphis-lions and the scale is preyed upon by the
same groups of insects as the purple scale.
Of the fungi which parasitize the purple scale only the red-
headed scale-fungus is found at all common on this scale and
there it is not nearly so efficient as on the purple scale.
Another fungus, however, does better work against this scale.
This is the pink scale-fungus (Page 302).
The same oil emulsions which are used against the purple
scale are the best for this one also. However, because of the
thick and heavy scale which fits the leaf or fruit very closely
the mature females and the young under the scales are not easily
killed. Therefore, to control effectively a heavy infestation of
this scale two sprayings may be necessary. The second should be
applied from four to six weeks after the first. This will give the
females that were not killed by the first spraying time to mature
and die and their last young to emerge, but will not allow suf-
ficient time for a new generation to mature and begin to pro-
duce young.


Bulletin 183, Insects of a Citrus Grove

Spraying with a 2% oil (i. e. twice the strength usually
recommended for purple scale and whitefly) has been recom-
mended for this scale. Trees sprayed with this strength of
oil should be thoroly dormant.
Fumigation with hydrocyanic acid gas (see p. 354) has been
particularly effective in combatting this scale. The average
kill secured during the past year in groves under the writer's
observation has been between 97 and 98%. The crawlers of
this scale do not have the tendency, so marked in the purple
scale, to crawl under other scales and into other protected
situations. As a result these scales are mostly found fully ex-
posed on the surface of the leaves (as often on the upper as on
the lower surface) and fruit where they receive the full effect
of the gas. Hence the percentage of kill is higher than in the
case of the purple scale.
In spraying fungus into a grove which has considerable
Florida red scale, the pink scale-fungus should be added to
the others if it can be obtained.
In addition to citrus, the Florida red scale infests many other
plants including the royal, coconut and many other palms, cam-
phor, magnolia, oleander, poinsettia, myrtle, and roses. In
spraying to control this scale any of these plants that may be
on the premises should also receive attention.

Chrysomphalus aurantii (Mask)
The California red scale which is one of the worst pests with
which the California grower has to contend is known to be pres-
ent in about two dozen localities in Florida. It does not seem to
be spreading rapidly nor to be likely to become a serious pest.
It has been in the State many years.
This scale also is round but is much flatter in outline and
lighter in color than the Florida red scale. The first larval skin
is not nearly so prominent and the scale is not as thick. In color
it is more yellowish. The most marked differences and those
which afford the most certain means of identification are found
in the mature female under the scale. In this species the female
is red instead of yellow, and heart-shaped instead of top-shaped
It is the color of the female thru the semi-transparent scale that
gives this scale the name "red." According to Prof. Rolfs (Fla.


Florida Agricultural Experiment Station

Ag. Exp. Sta. Bul. 117) the red-headed scale-fungus attacks this
scale. This may be the reason why this scale has never become
such a pest in Florida and in the more humid portions of the
West Indies that it has in California.
Chrysomphalus dictyospermi (Morg.)
The dictyospermum scale is intermediate in appearance be-
tween the California red scale and the Florida red scale. It is
generally distributed in Florida. Not much is known about
this scale on citrus here, but it does not seem likely to become
a serious pest. It attacks about 60 other plants in addition
to citrus. This scale will probably be found to be more easily
killed by the oil emulsions than is the Florida red scale.
This scale is a common and severe pest in the Mediterranean
region, and in South Africa is called the "Spanish Red Scale".
Pseudaonidia (Selenaspidus) articulatus (Morg.)
The Rufous scale is, as far as known, found in the State
only at Key West and Miami, where it infests the lime and
other plants. It is flat, nearly circular, and pale brown in color.
Besides citrus it attacks oleander, Ficus, palms, and a number
of other plants. It is common thruout the West Indies.
Pseudaonidia duelex (Ckll.)
This scale is not at present known to be in Florida, but- it
occurs in Louisiana and Alabama where it is a very severe.
pest on satsumas. This scale is apparently a very difficult one
to control and it is to be hoped that its spread into Florida will
be long delayed. As its name indicates, it was first noticed
as a pest of camphor trees and was probably introduced into
this country from Japan. It resembles somewhat in shape
the purple scale but is smaller and darker in color. Thoro
sprayings with oil emulsions have been used to control this
scale, but the most successful method seems to be fumigation
with hydrocyanic acid gas.
Aspidiotus perniciosus Comst.
The San Jose scale, a deadly pest of peaches, plums, pears,
and apples, attacks Citrus trifoliata. It has been reported as
temporarily attacking young orange trees in groves where orange


Bulletin 183, Insects of a Citrus Grove

trees are alternated with heavily infested peach trees. This is a
small scale, averaging only about half as wide as the Florida
red. It is gray in color and when only a few are present they
are easily overlooked. The first signs that the grower is apt
to notice are reddish or pinkish areas which develop about each
scale. When abundant they cover the bark and give the whole
tree their gray color.
The control of this scale on Citrus trifoliata would be best
accomplished by spraying with the red-headed and the black
scale-fungi in the summer and at some time in the winter when
the bushes are dormant and leafless with commercial lime-sul-
phur solution, 1 part in about 9 of water, as is recommended for
peach trees when they become infested with this scale. For a
table of dilutions for different strengths of lime-sulphur see
page 380. A 2% oil emulsion applied during the winter is
fully as effective as the lime-sulphur solution.

Parlatoria pergandii Comst.
As the name indicates, chaff scales are those thin, gray, or
brownish-gray scales which often completely cover the branches
of a tree and overlap each other, giving the tree the appearance
of being covered with chaff. It is partial to the smaller branches
and the trunks of small trees, but when the infestation is heavy
it is often found on the leaves and especially the fruit as well
as on the larger branches and trunks of larger trees.
The scale of the female is nearly circular in outline but is
usually bluntly pointed on one side. The first larval skin is
darker than the remainder of the scale and quite distinct from
it. It is oval in outline, has a prominent ridge down the middle,
and is placed nearer one edge of the scale, that is, it is not
central. This scale is a little smaller than the Florida red scale.
The adult female under the scale is dark purple, tinged with
yellow along the posterior margin. The young female is white.
The scale of the male is oblong and whitish in color. The first
larval skin is placed at one end and is about a third of the
length of the whole scale. It is greenish in color. The adult
male is purplish.
The female lays an average of about sixteen eggs. These are
large for the size of the female, hence the small number. The


Florida Agricultural Experiment Station

crawlers wander about for a few hours and then come to rest.
They show the same aversion to strong light as those of the
purple scale. This frequently causes them to crawl under an
old scale or into the depressions or pits of the fruit and settle
According to Hubbard, four generations are produced each
year. The crawlers of the first generation are especially abun-
dant in March or April and of the last in September or October,
but there is much overlapping and mixing of generations.
In addition to the ladybeetles and other predaceous checks
on scale-insects in general, this species is attacked by a wasp-
like parasite which does very efficient work in keeping it under
control. The grub of the parasite eats first the eggs and then
the mature female herself. When mature the adult parasite
escapes thru a hole in the scale.
The red-headed and the black scale-fungi attack this scale.
The latter does especially efficient work in controlling it.
This scale is easily killed by the oil emulsions, or fish-oil
soap alone. The best seasons for spraying are toward the end
of the seasons of maximum abundance of crawlers, which are
April and October. In groves that are sprayed regularly for
whitefly in May and September the chaff scale will cause no
trouble. The only extra precautions that need be taken when
considerable of this scale is noticed in a grove are to make a
special effort to secure and spread the black scale-fungus, and at
spraying time to see that the insecticide covers the branches as
well as the leaves and fruit.
Among the most common host plants of this scale are, besides
citrus, camphor, many palms, Ficus, japonica, mango, and ole-
ander. These plants also when growing in an infested grove
should be sprayed.
Chionaspis citri Comst.
The snow scale gets its name from the white color of the
male scales (Fig. 147). These, like those of the chaff scale, are
long and narrow. There is a prominent longitudinal ridge, and a


Bulletin 183, Insects of a Citrus Grove

fainter one on each side. .These three parallel ridges enable
the males of this species to be distinguished from those of the
chaff scale. The first larval skin is yellow-
ish in color. Owing to the inconspicuous
color of the females it is the male scales
that make a colony noticeable.
The scale of the female is dark brown
with a lighter margin, a color that re-
sembles the bark of the trees so closely
that the scales are hard to detect. In shape
it resembles somewhat the purple scale but
is broader. It has a prominent longitudi-
nal ridge which with the color and situ-
ation on the tree, readily distinguish it
from the purple scale. The first larval
skin is brownish-yellow.
Like the chaff scale, this one, too, in-
fests chiefly the branches but shows a
preference for the larger branches and is
often found on the trunks. It may so
drain the bark of sap as to cause it to die
and split.
Control is the same as for the chaff
In this group of unarmoredd) soft
scales, no true scale covering, separate Fig. 147.-S no w s c a le
from the body of the insect is formed, but (Ch"o"npi c itri.
the skin or body wall of the insect is hardened by a chitinous
secretion which is either incorporated into the skin itself or
formed into a layer on top of the skin. The female is not fast-
ened permanently to the bark of the tree, but is able to move
about until the eggs begin to form. At this time the legs are cov-
ered and made useless by the swelling of the body as the eggs
form and are more or less fastened to the branch or leaf, etc.
There are no marked molts in these scale-insects but only a
steady growth. The eggs are laid down under the female or
retained in her body until they hatch. The crawlers are oval,
active, six-legged creatures, much like those of the armored


Florida Agricultural Expel iment Station

scales. Males, of the species found on citrus, are rarely seen.
These scales suck the sap from the tissues like the armored scales
do, but the beak never grows to be very long and the insect is
able to withdraw and insert it at will.
The scales of this group give off honeydew abundantly. In it
the sooty mold grows so that an infested plant soon becomes
blackened. This honeydew is greatly relished by ants which
are seen constantly about the scales.
The soft scales are not nearly so destructive as the armored
ones. They are highly parasitized so that the colonies soon dis-
appear. They seldom seriously injure a mature tree, but on
nursery stock and on trees re-
cently set out the turtle-back
scale sometimes causes some
After death these scales soon
fall off the trees instead of re-
maining for many months as a
crust which partly shuts off the
light and air as do the armored
They are easily controlled by
the oil emulsions.
Coccus hesperidum (L.)
In this species and the next
described, the wax is incorpo-
rated with the skin which be-
comes tough and parchment-like,
resembling in appearance the
covering of the armored scales.
Fig. 148.-Turtle-back scale. (After (Fig. 148.) These scales are
Comstock.) larger than the armored scales
and thicker.
The full-grown female of the turtle-back scale is between an
eighth and a sixth of an inch long, oval in outline and dark
brown in color. It is much swollen in the center but flat at the
margin. The back is crossed by ridges which divide it into areas
suggesting the markings on the back of a turtle, hence the name.


Bulletin 183, Insects of a Citrus Grove

There are three notches in the margin, a shallow one on each side
and a deeper one behind. The scale of the male is very small.
The eggs hatch inside of the mother scale. The crawlers are
yellow and nearly transparent so that the color of the bark shows
thru them, making them inconspicuous. The skin is smooth and
shining. The margin of the body is extended outward as a thin
membrane which completely covers the six slender legs.
The young larvae attack only the young growth, leaves and
twigs. Consequently this scale increases most rapidly during
the flushes of growth in the spring and early summer.
This scale is attacked by at least a half dozen different
species of wasp-like internal parasites which keep it under good
control. These parasitized scales turn jet black.
The Cuban Aschersonia (Aschersonia cubensis) (see page
327) has been observed as a very effective fungous parasite of,'.i:
this scale in several instances by the Entomology Department '':
of the State Plant Board.
The early stages are easily killed by the oil emulsions and in
groves regularly sprayed with them for whiteflies and purple
scale the turtle-back scale will be controlled without any special
In addition to citrus this scale attacks a large number of
plants. Those with smooth bark or leaves are especially attrac-
tive to it. Ivy, oleander and japonica are favorites. Bay, avo-
cado, guava, persimmon, and many species of palms are some-
times attacked.

Saissetia hemisphaerica (Targ.)
The hemispherical scale is similar in size, color, and shape
to the turtle-back; but its center is more swollen and the margin
is narrower so that it is nearly hemispherical in profile, hence
the name. It averages about a seventh of an inch in length and
a trifle less in width. The height is about a twelfth of an inch.
The egg is about 1/150 of an inch in length and is yellowish-
This scale infests guava, avocado, asparagus, japonica, Ficus
spp., ferns, peach, rose, palms, and many other plants. Natu-
ral and artificial control are the same as for the turtle-back



Florida Agricultural Experiment Station

Saissetia oleae (Bern.)
The black scale (Fig. 149), the most destructive scale-insect
in southern California, is generally distributed in Florida. Here
it is more common on oleander than on citrus, which it rarely
attacks. It is also quite injurious to citrus in some of the West
Indies. In fact, Florida seems to be the
only important citrus center of the world
which does not have considerable trouble
with this scale.
The adult female is from an eighth to a
quarter of an inch long. It is black or
Sdark brown in color and nearly hemispher-
ical in shape. The markings on the back
form a distinct letter "H". It gives off
honeydew in great abundance.
The female lays from 300 to 3,000 eggs
and averages 1,700. She lives for two
months after reaching maturity and lays
from 50 to 100 eggs a day. They hatch
in from fifteen to twenty days. The young
prefer the leaves but migrate to the stems
before they are half grown. They grow
slowly, requiring from six to eight months
to reach maturity. Bul. 214 of the Cali-
fornia Station contains a full account of
this insect.
Fig. 149.-B lae k scale e. WAX SCALES
(From Quarterly Bul .
State Plant Board, Vol. Ceroplastes spp.
II, No. 1.)
The wax scales are soft scales which se-
crete a thick layer of white wax which completely covers the
body. This wax is soft and can be readily scraped off. Under-
neath the wax the skin proper is soft and delicate. These
scales give off abundant honeydew. Even a moderate infesta-
tion suffices to blacken thoroly the host plant.
There are three of these wax scales which are likely to be
found on citrus trees in Florida, but only the first is common.
Ceroplastes floridensis Comst.
The Florida wax scale when not stained by sooty mold or
other foreign matter is snow-white, often with a pinkish shade


Bulletin 183, Insects of a Citrus Grove

imparted to it by the red color of the insect beneath. When seen
against the deep green of the citrus leaf or stem it is a beautiful
object. However, its pure white wax, which is very similar to
the white wax of commerce, is commonly stained with the sooty
mold fungus which grows in the honeydew of the scale.
The full-grown female is an eighth of an inch or less in length,
oval in general outline but presents an angular appearance due
to the dome-shaped masses of wax on the back. (Fig. 150.) Of
these, there is one large rounded central dome surrounded by six
or eight lesser ones placed
in a circle about the margin -
of the scale and separated
from the central dome by a
The eggs are dark red
and about a hundredth of
an inch long. They aver-
age in number between 75
and 100 for each scale and
are placed under the female
which shrinks as they ac-
cumulate. The pale brown
crawlers show a preference
for the leaves where they
collect especially along the
midrib on the under side.
The young larvae are star-
shaped and even more beau- Fig. 150.-Florida wax scale. (From Quarterly
Bul. State Plant Board, Vol. II, No. 1.)
tiful than the adults. Three
or four months are required for growth and there are three
principal broods of crawlers which appear during April and
May, July and August, and October and November. The last
is a smaller, less important brood.
As the females mature and become heavy with eggs most of
them are unable to cling to the smooth surface of the orange
leaf and fall to the ground and perish. A larger proportion
of those that settle on the twigs are able to hang on until ma-
turity. Because of this mortality the insect never becomes a
serious pest of orange or grapefruit trees. On the thick angular
stems of Citrus trifoliata it can retain its hold much better and
sometimes becomes more of a pest. The native food plant of


Florida Agricultural Experiment Station

this insect is chiefly the gallberryy (Ilex glabra) of the flatwoods
which is commonly blackened by the sooty mold growing in the
honeydew given off by the insect. The mature females do not
fall off the gallberry.
Besides citrus and gallberry, this scale attacks avocados,
guavas, cherry laurel, sea grape, Ficus, loquat, mango and many
others. The writer has even seen it on sweet potato vines.
The Florida wax scale is parasitized by several wasp-like
insects whose grubs live inside the scale. The scale-eating cater-
pillar, Laetilia coccidivora Comst. (see mealybugs), sometimes
destroys this scale. This scale is also very effectively parasit-
ized by the turbinate fungus.
Should it become necessary to spray for this scale the oil
emulsions will probably be found perfectly satisfactory.
Ceroplastes cirripediformis Comst.
The Barnacle scale is closely related to the last
named which it resembles in appearance and life
history. Its most conspicuous difference is in its
height which is about equal to its width. (Fig.
151.) The waxy coat is dirty-white in color
mottled with brown and is divided into distinct
plates. These plates give the scales a hard, limy
appearance, and the angular outline which it
shares with the Florida wax scale, suggests a
barnacle in appearance, hence the name. It is
larger than the Florida wax scale, being a fifth
of an inch long and a sixth wide. It is a native
scale, found thruout the State, but nowhere is it
abundant. Besides citrus it infests guava and
wild persimmon, quince, and Eupatorium sp.
Its life history is similar to that of the Florida
wax scale. The eggs are larger and darker. The
crawlers are dark brown.
n arm e cae. Ceroplastes ceriferus (Anderson)
St 'et Blt The Japanese or Mexican wax scale has been
Board Vo. II. found in a number of localities in Florida, grow-
No. 1.)


Bulletin 183, Insects of a Citrus Grorve

ing on wild persimmon and gumbo limbo. Citrus, however, is
one of its host plants and will probably be found infested in
The wax of this species is not as symmetrically placed as in
the other species but forms a more irregular mass and has a
greasy appearance. The body of the insect is black or purplish-
brown and shows dimly thru the wax.
Pulvinaria pyriformis (Ckll.)
The pyriform scale (Fig. 152) is found on many plants, in-
cluding citrus, guava, mango, ivy, and many ornamentals. It
frequently becomes v e r y
abundant on avocados which
it blackens thoroly with the
sooty mold which grows in
its honeydew.
As its name indicates, the
mature female is pear-
shaped, tapering to a point
in front. It is brown but
nearly surrounded by a white
cottony-looking wax. This
cotton is also formed under
the posterior part of the
scale and serves as a protec-
tion to the eggs which are
laid in it. The full-grown fe-
male varies from a twelfth
to a sixth of an inch in
length. The young are oval,
greenish-yellow and without
any signs of cotton.
This scale is easily killed
by contact insecticides, as
the oil emulsions, soap solu-
tion, kerosene emulsion, etc.
The Cuban aschersonia
(Aschersonia cubensis) has
been frequently observed as
a very effective fungous Fig. 152.-Pyriform scale (Pulvinaria pyri-
parasite of this scale. formis) on guava leaf.


Florida Agricultural Experiment Station

Pulvinaria psidii Mask.
In Florida the green shield scale, which has been in the State
about 20 years, has attacked chiefly the wild rubber tree, the
guava, the mango, the sea grape, and the avocado in about the
order named. Only occasionally has it been taken from cit-
rus, altho it is said to be the worst pest citrus has in southeast-
ern Asia.
The adult female forms cotton even more abundantly than its
related species, the pyriform scale. The mass finally becomes
many times larger than the scale proper, which is about the

Fig. 153.-Green shield scale (Pulvinaria psidii) on mango leaf

size of the pyriform scale but more oval in outline, and lighter
in color. (Fig. 153.) It is greenish-brown. This scale is now
widely distributed in south Florida.

(By E. W. Berger)
A number of fungi do very effective work in parasitizing
soft scales. The following are the most important ones:


Bulletin 183, Insects of a Citrus Grove

CUBAN ASCHERSONIA.-This fungus* (Aschersonia cubensis)
(Fig. 154) forms buff and red pustules 1/16 to nearly 1/, inch
in diameter. It has frequently been collected effectively de-
stroying the liriodendron scale on the banana shrub here at
Gainesville. It appears to be widely distributed, however, and
has been recently received from Maitland, Kissimmee and New
Smyrna, Florida. Also from Porto Rico. The chief import-
ance of this fungus lies in the fact that it has been received in-
fecting and destroying the pyriform scale. This scale is a seri-
ous pest of a number of plants, particularly guava, avocado,
English ivy, rhynchospermum, camphor, cinnamon, etc., and a

Fig. 154.-Cuban Aschersonia on Pyriform Scale on guava leaf. Plant Board photo by
A. H. Beyer, courtesy of Experiment Station. Slightly reduced.

natural enemy like this was a desideratum. Pure cultures of
this fungus were first grown by the writer in 1920, and are
available for distribution.
This fungus has also been received on the following scales:
Soft brown scale (Coccus hesperidum) on citrus; liriodendron
scale (Toumeyella liriodendri), on banana shrub and magnolia;
tessellated scale (Eucalymnatus tessellatus), on mango from
Porto Rico.
TURBINATE FUNGUS.-This **(Aschersonia turbinata Berk.)
is the parasite that controls the Florida wax scale (Ceroplastes
floridensis). It produces one or several short whitish stems
that grow out from the mass of fungus covering the scale.
These stems approximate 1/16 of an inch in height and diam-
*According to Fetch (courtesy H. S. Fawcett, letter 1924) this has
perfect stage in Hypocrella epiphylla.
**According to Fawcett (1926) this has a perfect stage in Hypocrella
turbinata (Berk.) Petch.


Florida Agriculitural Experiment Station

eter and end in a shallow cavity containing the red or near-red
spores. It probably occurs wherever the Florida wax scale is
CEPHALOSPORIUM FUNGUS, Cephalosporium lecanii Zimmer-
man.-This fungus may be recognized as a delicate powdery
halo-like growth of light color about the margins of soft scales,
several species of which are effectively parasitized and con-
trolled by it. The same type of growth may, furthermore, cov-
er the entire insect. It has been received from the West Indies,
and various localities in Florida. The importance of this fun-
gus lies mainly in its being an effective parasite of the pyri-
form scale, which, while but a minor pest of citrus in Florida,
is a severe pest on guavas, avocados and some other plants.
Other insects that occasionally infest citrus in Florida and on
which this fungus may occur are: Soft brown scale (Coccus
hesperidum (Linn.) and the hemispherical scale (Saissetia
hemisphaerica (Targ.). It has been reported on Coccus (Le-
canium) viridis (Green) on citrus in Ceylon (Parkin, 1906, ac-
cording to.Fawcett, 1926) and received from Cuba on the same
scale infesting mistletoe.
This fungus has been received or reported from Florida or
elsewhere also on the following scales: Lecanium nigrofasci-
atum (Pergande) on bay; Coccus mangiferae (Green) on man-
go in the Virgin Islands: Coccus acuminatus (Sign.) on mango
in Barbados; liriodendron scale (Toumeyella liriodendri
(Gmel.) on magnolia and banana shrub; tessellated scale (Euca-
lymnatus tessellatus (Sign.) on palms and some other plants;
Toumeyella (Lecanium) turgida on pine (Pinus taeda) (Faw-
cett, Fla. Report, 1910).
This fungus can be readily grown artificially in pure cul-
Mealybugs derive their name from the mass of mealy wax
with which they cover themselves and especially their eggs. The
females retain their legs and antennae thruout life and are able
Sto move about during at least most of their lives.
They are very destructive insects and where not controlled
by parasites and predators are capable of killing a tree. For-
tunately, in Florida they are usually well controlled by those
natural checks. They give off large amounts of honeydew in


Bulletin 183, Insects of a Citrus Grove

which a particularly heavy growth of sooty mold develops, black-
ening the whole colony and all surrounding vegetation.

Pseudococcus citri (Risso.)
This mealybug is common over the entire State and is fre-
quently in evidence in a citrus grove, especially during the drier
portions of the year-spring and fall. It is likely to be

Fig. 155.-Citrus mealybug; infestation on grapefruit

found on any part of the tree but mostly in sheltered places such
as the angle between the petiole of the leaf and the stem. On
the limbs and trunk it gets into the crevices of the bark. The
mealybugs often collect around the stem end of a fruit. A
specially favored place is the sheltered nook formed by two or
more fruits in contact. This is more frequently the case with
grapefruit than with other citrus, consequently mealybugs are
rather more troublesome to grapefruit. Grapefruits become


Florida Agricultural Experiment Station

blackened with a particularly copious
and sticky honeydew which, with the
sooty-mold (Fig. 155) makes a vigor-
ous scrubbing necessary before they
can be packed.
The female grows to a length of from
one-tenth to a fourth of an inch. Her
I color varies from white to light brown,
Fig. 156.-A mealybug. (From with brown legs and antennae. (Fig.
Farmers' Bul 49.)
156.) The male is small, light colored,
and has two long white threads of wax projecting backward.
The female lays from 350 to 400 eggs in the mass of cotton
which she secretes. The eggs hatch in from eight to ten days
in summer, but twice this time is required in winter. The larvae
require from six to ten weeks to reach maturity. They are oval,
yellowish creatures. Their body fluids are also yellow as shown
when they are crushed.
Mealybugs are eaten by several other insects which may
usually be depended on to control them fairly well. Among such
predators are the ladybeetles and their larvae, the larvae of
lacewing flies, trash bugs, and syrphus-fly larvae, and the
scale-eating caterpillar, Laetilia coccidivora. The latter is a dark
red caterpillar a half inch in length. It makes covered passage-
ways of silk among the scales on which it feeds. The adult is a
grayish-brown moth a third of an inch long. The caterpillars
make their appearance in March and April. The moths appear
in June. There is another brood in the fall.
Ants carry mealybugs from tree to tree and to some extent
interfere with the insects that would otherwise feed upon them.

Entomophthora fumosa Speare
As summer rains come on mealybugs disappear, sometimes
quite abruptly. It has recently been shown by Dr. A. T. Speare,
formerly of the Bureau of Entomology, U. S. Department of
Agriculture, that this sudden disappearance is due to a fungus
that lives inside the bugs. Mealybugs killed by the fungus are
soft and spongy and "can be cut like cheese".


Bulletin 183, Insects of a Citrus Grove

Spraying is the best means of reducing the numbers. It is
important to have good pressure to force the liquid into corners
and crevices, which will also wash many of the insects from their
support. Washing them off the trees is so effective that spraying
with clear water is often sufficient to control them, yet it is
better to use an insecticide. One may use one of the oil emul-
sions which are recommended for whitefly, or fish-oil soap in
the proportion of 1 pound to from 4 to 6 gallons of water,
according to whether the water is soft or hard. Kerosene emul-
sion is fairly effective. To make this, dissolve 11/2 pounds of
soap in 3 gallons of hot water, add 3 gallons of kerosene and mix
by means of a pump; then dilute to 50 gallons. If one has a
power spray outfit with a good agitator he may use a simple
mixture of oil and water, taking 5 gallons of kerosene to 50
gallons of water, and mixing thoroly. However, unless one has
a good agitator he should not try this, as burning may result
from indifferent mixing. One of the best sprays is made by dis-
solving 2 1/3 pints of crude carbolic acid and 2 1/3 pounds of
fish-oil soap in hot water, and diluting to make 50 gallons of
spray. But one must use a good grade of carbolic acid. Car-
bolic acid varies a great deal in phenol content.
'Mealybugs are more abundant on some ornamentals than on
citrus. These, when grown about a citrus grove, may be a source
of infestation to the trees to which the bugs may be carried by
ants. If it is desired to grow these plants about the premises they
should be watched and treated when they become infested.
Among such plants are coleus, oleander, royal palm (roots),
and lantana. Mealybugs commonly infest seed potatoes which
are kept over summer for fall planting.

Pseudococcus longispinus (Targ.)
The long-tailed mealybug is much less common than the last
described, but is occasionally seen on citrus as well as the avo-
cado, mango, bamboo, oleander, coleus and croton. It is some-
what smaller than the common mealybug and is light yellow or
gray. The most prominent distinguishing characteristic is four
long threads of wax which project behind. The inner pair of
threads are especially long and conspicuous.
The work, life history, and control of the long-tailed mealybug
are the same as those of the common mealybug.


Florida Agricultural Experiment Station

Icerya purchase Mask.
This notorious pest of citrus, whose native home is Australia,
was introduced into Florida from California in 1893. It was
carried to California in 1868 and a dozen years later had
reached the citrus sections where it was so injurious as to
threaten to wipe out the entire industry. In this emergency
an entomologist, Koebele, was sent to Australia to learn why
it was not so injurious there and if a parasite or predator was
found to try to bring it to California. As a result of Koebele's
researches, the Vedalia or Australian lady-
beetle, Rodolia (Novius) cardinalis, was
found preying on the scale and was intro-
duced into California in 1889. It increased
rapidly and soon had the scale under con-
While this mealybug has never been as
serious a menace here as in California it
caused much trouble until, thru the efforts
of the Experiment Station, the Australian
ladybeetle was brought here also. The ex-
perience in California was repeated here.
The Vedalia never exterminates the scale
from a grove but always keeps it under
fair control. Sometimes the scale will in-
crease for a time and become quite con-
spicuous, but then the Vedalia also in-
creases and soon checks the scale.
For fifteen years the scale was confined
to the Pinellas Peninsula where it was first
introduced, but in 1912 it was found in
Tampa and from that commercial center
quickly spread to most of the citrus sections
of the State. It is now generally distrib-
uted thruout the State.
The cottony-cushion scale (Fig. 157) is
brown and has somewhat the appearance of
S a soft scale. When the egg-laying period
vri.a li 7 ybetae o arrives, the female forms a large mass of
usalia ehich elevates the posterior portion
cotony-cusihon scalthe cotton which elevates the posterior portion


Bulletin 183, Insects of a Citrus Grove

of her body until she stands almost on her head. This soft, cot-
tony cushion, in which the 500 to 800 eggs are laid may reach
a length of nearly a half inch, and is ridged lengthwise. Be-
cause of these longitudinal ridges this scale is also called "the
fluted scale." The adults are usually found on the bark of the
trunk, limbs, or twigs; but the young frequent the leaves, es-
pecially along the sides of the midrib. The young look much
like those of the mealybug, but when crushed they leave a red
stain. Both young and old have the mealybug habit of hiding
in the crevices and forks of twigs.
Besides citrus, the insects are partial to roses. The careless
shipping of cuttings about the State is probably responsible for
the rapid spread of the insect. It is abundant also on wormwood,
myrtle, mulberry, weeds and ornamentals. In the Annual Report
of the Florida Agricultural Experiment Station for 1915, page
lxxiv, is a longer list of host plants.
The time required for development varies from three to four
months or more, even in the summertime. There are about three
generations a year but no distinct broods. Like the mealybugs,
this scale increases most rapidly during the drier seasons of
the year but it is more apt to persist during the rainy season
than is the mealybug. Ants carry these insects from tree to
tree. A special effort should be made to control these pests in
a grove infested with cottony-cushion scale.
The cottony-cushion scale can be controlled by spraying. Ef-
ficient solutions are lime-sulphur and the oils which are used so
extensively against the whiteflies and purple scale. A lighter
oil is better, however, and at least one has been prepared and
placed on the market especially for use against this insect. As
in the case of mealybugs, high pressure is an important con-
sideration. On a few dooryard trees a frequent washing with a
strong soap solution may be effective.
The only permanent and satisfactory method of controlling
this scale in a large grove is by the introduction of the Australian
ladybeetle (Rodolia (Novius) cardinalis (Muls.)) (fig. 158).
This is much smaller than most of our native ladybeetles, be-
ing only one-eighth inch long. It is of a cardinal-red color,


Florida Agricultural Experiment Station

spotted and fringed with black. The larva (Fig. 157) which
also feed on the scale, is likewise red.
The female ladybeetle lays between 50 and 800 eggs. These
are brick-red in color and are most commonly laid on the cot-
tony sack of the female scales, but sometimes
S on the nearby branches. Each female lays up
to 50 eggs per day. The eggs hatch in five or
six days and the young larvae at once begin to
feed on the eggs of the scale. As they grow
larger they feed also on the scales, both old and
Fig. 1..--Australian young. The larvae require about three weeks
adlese (Roouia for growth and another week is spent in the pu-
larged drawing. pal stage. These pupae are scattered singly
about among the scales and are found most frequently on the
leaves. (Fig. 159.)
It is to be noted that a generation of the Vedalia requires but
a month while that of the cottony-cushion scale requires at least
three. This explains
the ability of the lady-
beetles to clean up an
infestation so quickly.
This is usually accom-
plished in three or four
months after the intro-
duction of the beetles.
Except for an occa-
sional citrus aphid, Ve-
dalia feeds only on cot-
tony-cushion scale or
on each other if the
scale becomes scarce.
Therefore, when the
supply of scale in a
grove runs low, the Ve-
dalia may die out. Af-
ter the disappearance
of the beetles, the scale
may agairi multiply in
the grove.' It nlay then
be necessary to 'rein-
troduce the Vdli'a al- ~g. 159.--Pupae of the tuAustralian ladybeetle. Twice


Bulletin 183, Insects of a Citrus Grove

tho experience in Florida has shown this to be seldom neces-
sary. As soon as the scale again becomes abundant, the beetles
almost invariably reappear, probably flying from adjoining
groves. Some observations of the writer show that the Vedalia
has found a colony of the cottony-cushion scale at least two
miles from the grove where the beetles hatched. (Fla. Ag. Exp.
Sta. Ann. Rep. 1915, p. lxxv.)
Colonies of the Vedalia are being supplied to the growers at
the cost of collection, by the Entomological Department of the
State Plant Board, Gainesville.
Our native twice-stabbed ladybeetle (Fig. 140) does good
work against this as well as other scales, but it cannot be de-
pended upon to control the scale as well as the Vedalia. Trash
bugs and the scale-eating caterpillar have also been seen to feed
upon this scale.
A fungous disease belonging to the family of Phymatasporae
was observed by H. A. Gossard in 1899 (Fla. Bul. 56) to de-
stroy "more scales than any other agency" during periods when
it became epidemic. The present Entomologist and Associate
Entomologist of the State Plant Board have also repeatedly
observed a fungus, probably the same one observed by Gossard,
as effectively destroying the cottony-cushion scale. The Entomol-
ogist of the Plant Board has found it an easy matter to grow
this fungus artificially in pure cultures like the Aschersonias
(see under Whiteflies).

Eight species of whiteflies have been found on citrus in
Florida. In the order of their abundance they are:
(1) The common whitefly, Dialeurodes citri (Ash.)
(2) Cloudy-winged whitefly, D. citrifolii (Morg.)
(3) Woolly whitefly, Aleurothrixus howardi (Quaint.)
(4) Flocculent whitefly, A. floccosus (Mask.)
(5) Bay whitefly, Paraleurodes perseae (Quaint.)
(6) Inconspicuous, or sweet-potato whitefly,
Bemisia inconspicua (Quaint.)
(7) Mulberry whitefly, Ti eurodes mori (Quaint.)
(8) Guava whitefly, Tri es floridensis (Quaint.)
Whiteflies are sucking inse Indeed, they are quite close-
ly related to scale-insects, and like them the larval stages are


Florida Agricultural Experiment Station

flat scale-like creatures and (except the first stage, which is an
active "crawler") are immovably fastened to the host. The
most conspicuous difference is that instead of only the males
possessing wings and flying about as in scale-insects, both sexes
are winged and active. The presence of winged females en-
ables the insect to spread much more rapidly from tree to tree
and from grove to grove than can scale-insects and greatly in-
creases the difficulty of control.

The life history of all whiteflies is very similar and one dis-
cussion will answer for all, altho the time spent in development
will vary with different species. As with all insects, there are
four stages in the de-
velopment of the
whitefly,-egg, larva,
pupa, and adult or im-
SThe whitefly egg is
nearly oval in outline,
and very small. It
is usually less than one
hundredth of an inch
long and about half as
Fig. 160.-Citrus whitefly: Adults and eggs, on leaf. wide, barely visible to
(iFrom Bul. 97.) wide, barely visible to
the unaided eye. When
abundant the eggs give the citrus leaves an appearance of being
covered with a mealy dust. (Fig. 160.) The eggs are laid on
the under side of the leaves of the host plants to which they are
fastened by a short stalk. The eggs hatch in a few days into
pale yellow, flat "crawlers" which have six extremely short legs.
These larvae crawl about for a few hours, but have a distinct
aversion to strong light, which keeps them on the lower side of
the leaves. Soon they insert their beaks into the tissue and begin
to suck the sap. After this the larva (Figs. 161 and 167) never
move again, but remain where they anchored themselves; oval,
exceedingly flat objects which lie closely pressed against the
surface of the leaf to which they hang by means of their sucking
mouth parts. They grow so rapidly that within a few days their
body walls become incapable of any longer accommodating the
insects. The skins are then cast off, moltedd." At this time the
legs and feelers are lost so that the second-stage larva seems


Bulletin 183, Insects of a Citrus Grove

scarcely to resemble an insect, as commonly known. This process
is repeated twice.
The fourth stage larva (Figs. 163 and 168) differs consider-
ably from the larva in other stages. It takes
much less food, is thicker, and the organs of
Sthe adult whitefly begin to form. This stage
corresponds to the pupal stage of most insects
in which there is more difference between the
stages. After a more or less prolonged pupal
Fig. 161.-The Cali- stage (the time spent in this stage depends
forna wadhitefy- much upon the temperature) the pupal case
(DPla t a t- splits across the back and the adult insect
linee. Enlarged
drawing, emerges. In this stage the insect differs
greatly from the larva. It has the typi-
cal three parts of the usual insect body
-head, thorax, and abdomen-and is pro-
vided with two wings. These are covered
with mealy or dust-like scales which make
the wings look white, whence the name
whitefly. These insects are also known as
"mealy wings" in entomological literature,
a name never used by Florida growers. The
bodies of these insects are usually yellow
or orange. The sexes are very similar in
appearance, altho the male is a bit smaller Fig. 162.-Citrus whitefly:
First-stage 'larva. (From
than the female. Bu. 97.)

Dialeurodes citri (Ash.)
This is by far the most common of the whiteflies and the one
the grower has in mind when he speaks of "whitefly". Fif-
teen or twenty years ago it was our most destructive citrus in-
sect and still holds that distinction in the satsuma belt. Dur-
ing the past few years, however, it has undergone a striking
reduction in numbers in the peninsular part of the state. It
still, however, does an immense amount of damage. It injures
citrus trees in three ways:
(1) It withdraws immense quantities of sap from the trees.
This loss of sap is a serious drain on the trees, checking their
growth and that of the fruit. The fruits on badly infested trees
are always fewer and inferior in quality.


Florida Agricultural Experiment Station

(2) The larvae of whiteflies throw off from their alimentary
tract large quantities of a sweetish nectar-like substance called
honeydew. This falls on the leaves and fruit, and in this honey-
dew grows a jet-black fungus called "sooty mold."
Sooty mold blackens the entire tree including the fruit which
requires washing before it can be packed. Washing adds to the
expense of packing and introduces a new liability for loss of
fruit from scratches and inoculation with the spores of fungi
that cause decay. This blackening of the tree is the most
conspicuous sign of the presence of whitefly and the one that
most frequently engages the grower's attention. Indeed, many
growers judge of the presence of the whitefly in their trees solely
by the sooty mold. However, it is probable that this blackening
effect is really a much less
serious matter than the loss
"- of sap.
Sooty mold injures the
trees in another way; the
shade it produces cuts off
much of the light from the
Slaves and thus interferes
with the production of
(3) The sooty mold is in-
directly responsible for an
increase in the amount of
purple and long scale. This
relation has be en treated
under purple scale.
Fig. 163.-Common whitefly: Fourth-stage The eggs (Fig. 164) of this
larva. (From Bul. 97.)
species are pale yellow and
are scattered singly over the leaves, a marked preference being
shown for young leaves. Each female lays about a hundred eggs
in the course of her life of a week or ten days. Most of them
hatch in from ten to twelve days. The summer brood spends
about three weeks in the larval stages; the others a little longer,
up to five weeks. The spring and summer broods usually spend
about two weeks in the pupal stage; the autumn brood from
four to ten months (Morrill and Back, 1911). There are three
main generations each year. In the latter part of the summer
these become much confused. The spring brood of adults is


Bulletin 183, Insects of a Citrus Grove

at its maximum, taking the average for the whole State, in
the latter part of March. They appear earlier in the south
than in the north. In addition, there may be a partial brood
in January or February in the extreme southern part of the
State. The summer brood is on the wing in June, and the
last and usually the largest brood the latter part of August or
early September. (Fig. 165.)


The common whitefly has been observed to mature on the fol-
lowing plants, arranged approximately in order of preference:

Chinaberry and umbrella tree
Citrus, all varieties and species
Round oranges
Cape jasmine (Gardenia)
Prickly ash
Japanese persimmons

Less Severely Infested
Laurel cherry
Smilax sp.
Wild olive (Osmanthus americanus)
Green ash
Japonica (Camellia japonica)
Jessamine (Jasminum sp.)
English ivy
Native persimmon
Water oak
Trumpet flower (Tecoma radicans)
Ficus sp.
Scrub palmetto
Viburnum nudum
Button bush (Cephalanthus occiden-
Boston ivy
Mexican orange (Choisya ternata)
Osage orange (Maclura aurantiaca)
Portugal cherry (Cerasus sp.)
Tree-of-Heaven (Ailanthus)

The wild and useless plants in the above list, particularly
those near the head, should be destroyed when growing near
groves. Of these the China and umbrella trees are particularly
important. The planting of these trees in citrus communities
should be prohibited by public sentiment and by law. It has
been estimated that a good-sized Chinaberry tree will produce
on the average between 25,000,000 and 50,000,000 whiteflies
each season. From these trees the adults of the late summer
brood fly out to infest citrus trees when the maturing leaves of
the Chinaberry are no longer attractive.


Florida Agricultural Experiment Station

There are but few insects, and virtually no higher animals,
that feed upon this species. This is undoubtedly because it is an
imported insect which has left its enemies behind. In India,
which is probably the
native home of this
species, there are sev-
eral insects which prey
upon or parasitize it,
and an unsuccessful
attempt was once made
to introduce some of
them (Woglum, 19.13).
The twice stabbed
ladybeetle (described
under purple scale)
(Fig. 13 9) destroys
some crawlers and oc-
casionally an older
larva, but prefers
Fig. 164.-Eggs of common whitefly. .Magnified other food, especially
(From Bl. 97.) scale crawlers. A tiny,
dark brown ladybeetle, Delphastus pusillus (Lec.) seems to be
very fond of the eggs, but for some unknown reason never be-
comes sufficiently abundant to be of much practical benefit. A
related species, Delphastus catalinae, a very efficient enemy of

i i 11 I I 1 1 f I I i II I I 1
I| I I9 1 1 i 9 I 1I I I 3 I
I 9 I I I I I I3 r 9 3 | J ti1 I I .
9 II ( I I I 14 I I I 1. i
11I I I

II If 9 39 1 \i -, I I I 3 9 1 1 i
I F 9 I .*3 9f I II
St fji -11 I ~ 1 1 1 1 I -l1 yh I
S-. I I -- .9 1. i I? I I 1.'' 1, iJ
r T I 9 il 9 I
i ,i I i I I A 9..- A \I 9.
,-- I\I I9I -, -. J I f\ 91
-I. _'._ L- _J.1 _I_.I _L J- -L'}
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
Woolly whitefly. ---- Common citrau whitefly. ..... Cloudy-winged whitefly.
Fig. 165.-Diagram showing relative date of emergence of adult whiteflies. (From But. 126.)


Bulletin 183, Insects of a Citrus Grove

another whitefly in California, feeds greedily upon whitefly
eggs, and has been introduced into Florida by the Experiment
Dialeurodes citrifolii (Morgan)
The cloudy-winged whitefly is very similar to the common
whitefly; so similar indeed that for many years they were
considered as a single species. Dr. E. W. Berger, then ento-
mologist to the Experiment Station, first separated the two spe-
cies. He named this insect Aleurodes nubifera. The most
marked differences are in the egg, which is black in this species
(Fig. 166), and in the fact that this species is attacked by an-
other species of
fungus, the yellow B
aschersonia, in ad-
dition to those
that attack the
common whitefl v.
Black eggs iori
the yellow fungus
on the leaves \\ill iI I
at once acquaint i
the grower with
the presence ,of
the cloudy-winged
whitefly. Ij'..n. a
few localities and. .
in isolated groves
in the southern 'ig. 66.-Eggs of cloudy-winged whitefly. Magnified. (From
part of the State,
the cloudy-winged species only is found, but in most groves
where it occurs the common whitefly occurs with it. The
cloudy-winged species does not commonly occur in the north-
ern part of the citrus belt. Before the "big freeze" of 1894-95
this species was found over the entire citrus belt, but as its
food* in Florida is confined entirely to citrus it was extermi-
nated thruout the northern part of the citrus belt by the entire
loss of the leaves from the trees in that region.

*It has been reported as infesting Ficus nitida in Cuba, the guava in
Porto Rico, and the tomato in New Zealand.


Florida Agricultural Experiment Station

The egg is about the size and shape of those of citri, but is
black in color, and is covered with a network of ridges. (Fig.
166.) The females of this species show
an even greater fondness for new growth,
particularly watersprouts, t h a n does
citri. The leaves of watersprouts are
often so thickly strewn with eggs as to be
distinctly blackened.
The larvae (Figs. 167 and 168) closely
resemble those of citri but have a thinner
skin; so much thinner, in fact, that. when
the adult emerges from the pupal case
the case collapses instead of maintaining
Fig. 167. Cloudy-winged its shape as does that of citri.
whitefly: Firstage lar- The adult, too, is similar but in the
va. (From Bul. 97.)
middle of each wing there is a darkened
area which gives rise to the insect's name, cloudy-winged.
The wings are not held as high as in citri, and more of
the abdomen shows.

The life history re-
quires about two
weeks longer during
the summer than that
of citri, consequently
there is no imperfect
winter brood as with
citri and the summer
broods lag behind
those of that species,
as shown in the dia-
gram (Fig. 165.)
The maximum
flight of the spring
brood of adults oc-
curs in early April,
about three weeks _
later than that of cit-
ri; the summer brood Fig. 168.-Cloudy-winged whitefly: Fourth-stage larva.
ri; the summer brood (From Bul. 97.)


Bulletin 183, Insects of a Citrus Grove

in the first half of July. a month later; and the last brood in
late October, about seven weeks after that of citri.
The same oil emulsions which are used against the common
whitefly are used against the cloudy-winged also. The only
modification of the spraying procedure desirable is in the time
of applying the spray.
Whenever the two species are present, the common whitefly
is the more important and the cloudy-winged species becomes
of secondary importance. In this case spray at the time recom-
mended for the common species. Altho not the most favorable
time for the cloudy-winged species, spraying at that time will
virtually control it. In the few groves where the cloudy-winged
only is present, spraying should be delayed from three to seven
weeks; that is, spray in early May, August 1, and November 1.
In groves in which the cloudy-winged species is abundant,
one can do a great deal toward effecting control by removing
the watersprouts at certain periods. These periods will be
when most of the eggs have been laid and but few adults have
emerged; in other words, when the fewest adults are about.
These periods will be in the middle of May, middle of August,
and some time in December, January or February.
In spraying the fungi where this species is present, the yel-
low aschersonia should be added to the others.
Aleurothrizus howardi (Quaintance)
The woolly whitefly was first observed infesting citrus in
Florida in 1909, when E. A. Back of the Bureau of Entomology,
U. S. D. A., discovered it in Tampa. It had been observed as
a pest of citrus in Cuba six years previously. It was thought
that the insect had been introduced from Cuba into Tampa;
however, Dr. A. L. Quaintance, our foremost authority on
this group of insects, states that it is identical with the
whitefly which was collected from the sea grape (Coccolobus)
twenty-five years ago, and is probably native to Florida. Yet
the history of the insect as a citrus pest in Florida shows plainly
that it has spread from the infestation in Tampa. (Fla. Agr.
Exp. Sta. Bul. 126.) It would seem most probable then that,
altho it is a native insect which has long lived on the sea grape,
it has comparatively recently developed a strain which has taken


Florida Agricultural Experiment Station

to citrus. From the fact that it was first discovered as a citrus
pest in the West Indies it seems probable that this supposed
citrus strain developed elsewhere and was introduced into Flor-
ida about 1908. It is now spread over most of the state.
For a few years after its introduction it threatened to be a
first class pest and in a few groves did a great deal of damage,
(see Fla. Agr. Exp. Sta. Bul. 126) but it was quickly subdued
by a little wasp-like parasite, Eretmocerrs
S haldemani. (Fig. 169.)
The dense mat of wool which persists for
months on the leaves makes an excellent place
in which the young of the purple scale can
S. ', hide, and much woolly whitefly in a grove has
-. 4 f always been followed by a heavy infestation
Sof purple scale. This is perhaps the most se-
rious phase of an infestation of woolly whitefly.
Fig. 169.-Eretmoce-
rus haldemani: DESCRIPTION
Male. Greatly en-
arged. (From Bul. The woolly whitefly differs more from the
two other species than they do from each other.
The name is derived from curled waxy filaments which com-
pletely cover the pupa and have the appearance of wool. The
empty pupal cases of this species are very persistent and remain
on the leaves for many months after the adults have emerged.
The eggs are brown in color, and curved in shape somewhat
like a short sausage. They are laid mostly in circles (Fig. 170).
This results from the habits of the female during egg laying.
She inserts her beak into the tissue of the leaf and, on that as a
pivot, rotates her body. The female does not choose the very
youngest and most tender leaves on which to lay eggs as do
those of the other species, but leaves more nearly mature, and
often lays on the leaf on which she herself was raised.
The first-stage larvae are light green, with well defined legs
and antennae. The other stages are dark brown in color, black
if parasitized, and widely fringed with a corona of shining
white waxy plates. The larvae give off honeydew copiously
and there is usually a drop clinging to them during their entire
life. In the third stage the woolly covering develops.
The adults are distinctly more yellow than those of the two
preceding species and do not hold their wings so high. They
are very sluggish, seldom taking to wing and then flying only
short distances. On the other hand, they will cling tenaciously


Bulletin 183, Insects of a Citrus Grove

to one's clothing and doubtless are thus carried long distances.
There are four distinct broods a year, with adults flying from
December to February, the last of May, the last of July, and the
first of September.
Altho both the red aschersonia and the brown fungus have
been found on this species, they are not nearly as efficient as
on the others. A species of Cladosporium does better, but the

Fig. 170.-Leaf infested with woolly whitefly. (From Bul. 126.)
chief parasite is a small wasp-like insect, Eretmocerus halde-
mani. This insect lays its eggs in the larvae of the whitefly.
The grub of the parasite feeds on the substance of the whitefly
larva and finally kills it. The parasite pupates inside of its
host which markedly swells up, and about the time the adult
whitefly should emerge the wasp-like parasite comes out thru
a round hole that it cuts in the top of the pupal case of the dead
whitefly. These parasites are so abundant that they have in-
variably controlled infestations of this whitefly, and, usually
before any serious harm has been done.
Should this insect become sufficiently abundant to threaten,
it may be controlled by the same oil sprays that are recommended
for use against the other species. It is imperative, however, that
the oil be applied before many of the larvae have reached the


Florida Agricultural Experiment Station

third stage, as the dense mat of wool more or less smeared over
with honeydew, protects the third- and fourth-stage larvae from
the oil. The most favorable periods for spraying are late Feb-
ruary or early March, early June, the middle of August, and
about November 1. (Fig. 165.)

Minor Species
Aleurothrixus floccosus (Maskell)
Associated with the woolly whitefly, often on the same leaf, is
a closely related species, the flocculent whitefly, which can be
distinguished only by a microscopical examination. (Jl. Ag.
Res., VI-No. 12, Quaintance & Baker.)

Trialeurodes floridensis (Quaint.)
The guava whitefly which is often quite abundant on guavas
and avocados is rarely found on citrus. It resembles D. citri,
but the larva is smaller, somewhat thicker and more yellow
in color.
Paraleurodes perseae (Quaintance)
The bay whitefly resembles somewhat the woolly whitefly in
the larval stages so that one might easily confuse them. But
this species lacks the curly wool, altho it has the straight waxy
plates. These plates break up when the adult emerges from the
pupal case, into short rods which are scattered about the slug-
gish winged insect which squats in the center, presenting an
appearance suggestive of a sitting hen surrounded by straw.
Instead of being curled and woolly these rods are nearly straight.
As its name suggests, this whitefly's native food plant is the bay
(Tamala). It is a common sight in citrus groves but the insects
seldom become abundant. Only once has the writer seen a grove
that needed spraying for this species alone. It is also found on
the avocado.
Doubtless it would yield readily to the same oil sprays that
are used to control the other species.
Bemnisia inconspicua (Quaintance)
The inconspicuous or sweet-potato whitefly is a common pest
of sweet potatoes in the southern part of the State and occa-
sionally gets on the citrus trees. It is markedly-smaller both in


Bulletin 183, Insects of a Citrus Grove

the larval and adult stages than the other whiteflies. Otherwise,
it resembles citri quite closely. It is parasitized by the red
aschersonia. It has never been sufficiently abundant to demand
control measures. Should it ever become so, it can doubtless be
controlled by the same oil emulsions recommended for other
Tetraleurodes mori (Quaintance)
The larva of the mulberry whitefly is a small jet-black insect
with a wide fringe of white wax. It resembles the younger
stages of the woolly whitefly but is smaller, black, and never
develops the curly wool-like, waxy filaments. Altho present on
a variety of trees, including the mulberry and persimmon, it
has never given any trouble to citrus growers in Florida. How-
ever, the same insect, or at the most a variety or strain of it,
is said to be a serious pest of oranges in Mexico.

Other Whiteflies
There are five other species of whitefly in other parts of the
world, that are more or less serious pests of citrus. One of
the most serious, the spiny blackfly (Aleurocanthus woglumi
Ashby), is dangerously near Florida. It has recently been in-
troduced into Cuba and the Bahamas. Like the two species
most troublesome to citrus, its native home is in southeastern
Asia. The adjective "spiny" refers to the pupal case and not
to the adult fly. "Black" applies to both the larvae and the
adults. As the body of the adult is dark brown and the wings
smoky with a white cross, the general impression to the unaided
eye is bluish-black. Altho stated by the Imperial Entomologist
of Jamaica to yield to oil emulsions it is undoubtedly a danger-
ous insect and the efforts of the State Plant Board to keep it
out of Florida should receive the hearty support of all citrus
(By Dr. E. W. Berger)
RED ASCHERSONIA.-Also known as the red whitefly-fungus
(Aschersonia aleyrodis Webber). This fungus (Fig. 171) was
first studied in the early 90's by Dr. H. J. Webber, then of the
United States Department of Agriculture, about Crescent City,
Citra, Panasofkee, and other places, in Florida. It forms pink


Florida Agricultural Experiment Station

and red pustules one eighth of an inch or less in diameter. The
color of the fungus is pink but the spores are bright red and
give it the red color. It is an important factor in the control
of the common whitefly (Dialeurodes citri), and cloudy-winged
whitefly (Dialeurodes citrifolii), both on citrus. The writer
has also observed it abundantly infecting a whitefly on sweet
potato, probably Bemisia inconspicua, and specimens of an un-
known black aleurodid heavily infected by this fungus have
been received from Fort Myers, Florida. Other aleurodidae

Fig. 171.-Red Whitefly-Fungus or Red Aschersonia. Roundish white areas
with black centers are the pink and red fungus pustules. Natural size.

at times also become slightly infected with it. According to
records kept by the Entomological Department of the State
Plant Board, this fungus appears to be a useful parasite of the
black fly (Aleurocanthus woglumi) in Cuba, Jamaica, and Costa
This is the fungus that was first grown in pure cultures by
the Plant Board, based on methods perfected by Dr. H. S. Faw-
cett while at the Florida Experiment Station.
YELLOW ASCHERSONIA.-Or yellow whitefly-fungus *(Aseher-
sonia goldiana, Sacc. et Ellis), was discovered at Winter Park,
Florida, by Prof. P. H. Rolfs in 1906. It resembles the red
aschersonia (Fig. 171) in general appearance, except that it is
a bright lemon yellow when fresh. It is, however, effective only

*A. flavo-citrina P. Henn.


Bulletin 183, Insects of a Citrus Grove

against the cloudy-winged whitefly (Dialerodes citrifolii) of
citrus but is regarded by some as more effective against this
whitefly than the red aschersonia. Pure cultures of this fun-
gus are available.
BROWN WHITEFLY-FUNGUS.-Figure 172 is an excellent illus-
tration of this fungus (Aegerita webberi Fawcett). The fun-
gus was discovered in 1896 by Dr. H. J. Webber at Manatee.
Florida. It was only later (1910) given its scientific name by
Dr. H. S. Fawcett, who discovered its spores, thus enabling him
to classify it. It forms brown pustules about one eighth of an

Fig 172.-Brown Whitefly-Fungus. Natural size. Round black areas are the
fungus pustules

inch in diameter on the underside of the leaves of citrus in-
fested either by the common whitefly (Dialeurodes citri) or the
cloudy-winged whitefly (Dialeurodes citrifolii). As this fun-
gus, when once established on a leaf, sends out fine threads
which grow from one infected whitefly larva to another until
every larva has been reached and killed, it is unusually effec-
tive. It also thrives later in the season after dry weather has
set in. This fact is probably due to its habit of growth just
explained. The fine fungal threads referred to also finally grow
around the edge of the leaf and eventually form a fine tissue-like
growth on the upper surface on which the brown spore-bodies
are formed. When the fungus is fruiting or producing spores
the leaves show a cinnamon-brown color on top. While most of


Florida Agricultural Experiment Station

the spores are formed on top of the leaf, some also are formed
underneath. Unfortunately, methods for growing this fungus
in pure cultures have never been successful.
The records of the Entomological Department of the State
Plant Board also show this fungus as a useful parasite of the
black fly (Aleurocanthus woglumi) in Cuba, where the latter
infests citrus and other plants.
WHITE-FRINGE FUNGUS.-This fungus, *(Fusarium aleyrodis
Petch) was first noticed by Professor P. H. Rolfs, in 1907, at
Sutherland, Florida. It has since then been found widely dis-
tributed throughout the State. According to investigations
made at the Experiment Station, it is this fungus which is the
cause of the so-called "natural mortality" of whiteflies, when
all but a few whitefly larvae on a large majority of leaves die.
As its name indicates, the growth of this fungus outside of
the whitefly larvae is a white fringe, very delicate and easily
blown away, so that it is difficult to preserve. But it is a fairly
safe assumption that, whenever large numbers of whitefly lar-
vae die without evidence of another cause, it is the white-fringe
fungus that is present. It is found on both the common white-
fly and the cloudy-winged whitefly. As this fungus appears to
be so universally present, ready to destroy whitefly larvae
whenever favorable weather conditions arise, propagation of it
has not been undertaken, although it is easily grown in pure
CINNAMON FUNGUS. T h i s (Verticillium heterocladum
Penz.) occurs every now and then on citrus, infecting whitefly
larvae, chaff scale, soft brown scale, the purple scale and long
scale. It also infects these same and other similar insects on
other plants. In appearance its pustules are like the brown
fungus but with a powdery surface and cinnamon color. It is
widely distributed.
Pure cultures of this fungus were produced by Dr. H. S.
Fawcett in 1908, but as the fungus has not been considered of
the same importance as the several others, propagation of it
has not been undertaken commercially.
As stated under the heading of purple scale, the control of
whiteflies and scale-insects is a single problem; the control
measures are the same.
*Microcera sp. Fawcett.


Bulletin 183, Insects of a Citrus Grove

The common method of controlling whiteflies and purple
scale in Florida is to spray the trees with an oil emulsion.
Time to Spray.-We have seen that there are three broods
of whiteflies. One is on the wing largely during the last of
August and first of September, another during the last of
March and the third in June. As whiteflies may fly several
miles, it is evident that a grove may be reinfested from neigh-
boring groves at each flight, necessitating control measures for
each brood. However, the summer brood, the adults of which are
on the wing in June, can usually be ignored as far as spraying is
concerned as the entomogenous fungi ordinarily will control it
very well. This leaves the fall and the spring brood to be dealt
with by insecticides. Ordinarily the average grove will need to
be sprayed for one or both of these broods in connection with
the control of purple scale. As we have seen, the eggs of the
whitefly hatch in about a week. The younger the larvae the
more easily they are killed. Therefore it is important to spray
as soon as practically all the eggs have hatched. Another rea-
son for spraying early in the life history of the whitefly is to
avoid the drain on the trees resulting from the feeding of the
larvae. To spray the trees after the larvae have done much of
their damage would be somewhat like locking the barn after
the horse has been stolen. Altho most of the fall brood of white-
flies are usually on the wing during the last of August and the
first week in September, there are a good many slowly develoo-
ing individuals that come straggling along during the early part
of September. So it is usually well along in September before
the flight of the adults can be said to be over. This will vary
in different parts of the state and in the same grove from year
to year. The grower should watch the flight of the fall brood
of whiteflies and when they have practically all disappeared
he should mark down the date. He should then wait ten days
so that practically all the eggs will have hatched. The expira-
tion of this time will mark the most favorable time to spray for
whiteflies. This will bring the date to the last part of Septem-
ber ordinarily.
Moreover, it is difficult to spray a grove during the summer
rainy season when there is apt to be a shower two afternoons
out of three. The trees must be dry before they are sprayed.
If there is water standing on the leaves it will dilute the spray


Florida Agricultural Experiment Station

solution and make it ineffective. Sometime then in late Sep-
tember or early October, conditions are usually right for spray-
ing with oil emulsions for whiteflies and scale-insects and the
spraying should be done promptly for the reasons given above.
Moreover, growers like to get this fall spraying out of the way
before the picking season opens. If the fruit has much of a
coating of sooty mold this spraying will help to loosen it and
aid in getting rid of it in the packing house.
One exception, however, must be made to early fall spray-
ing. In the case of early varieties such at satsumas, Parson
Brown oranges, etc., the fall spraying should be delayed until
after the fruit has been picked. As recently (Farmers' Week
Address, 1926), pointed out by Mr. W. W. Others, spraying
with oil emulsions delays the ripening of the fruit. In the case
of the early varieties the price is usually so much better early
in the season that the grower cannot afford to delay the ripen-
ing of his fruit except in the case of a very heavy infestation.
As stated above, the spring brood of the common whitefly
is on the wing in late March. Again the growers should wait
until the brood has disappeared and ten additional days to al-
low the eggs to hatch. This would bring the spraying in April,
but it is not quite safe to spray when the fruit is too small. It
is, therefore, usually recommended that growers postpone this
spring spraying until the spring flush of growth has matured
and the trees have become partially dormant and the fruit has
reached the diameter of approximately an inch. This will bring
the spring spraying sometime in May.
Of course it will not always be necessary to apply both of
these sprayings to a grove. If the trees are free of scale-insects
or whiteflies there is nothing to be gained by the costly spray-
ing. However, a good clean-up spray, particularly in the early
fall, is much to be recommended, as trees thoroly sprayed at
this time should remain reasonably free of insect pests thruout
the winter.
Under special conditions it may be desirable to apply the oil
emulsions at other times. Trees sprayed with Bordeaux to
control scab or melanose should always be sprayed within two
months with an oil emulsion to counteract the increase of scale-
insects due to the killing of the entomogenous fungi by the Bor-
deaux. This is very important. If a grove becomes heavily in-
fested with scale-insects during the winter it should, of course,


Bulletin 183, Insects of a Citrus Grove

be sprayed before the spring flush of growth makes spraying
Spraying Solutions.-The spray solutions which have been
most used are emulsions of lubricating oils. These are made by
thoroly emulsifying a paraffin oil with soap and water. There
are two government formulae, both developed by Mr. W. W.
Others of the Bureau of Entomology, stationed at Orlando.
One does not need any heat and is called "cold mix". It is as
Fish-oil soap ......................... ............... 8 lbs. or 1 gallon
Lubricating oil, 24 or 28 Baume .............. 2 gallons
Water ................... ................... 1 gallon
For this emulsion, oils similar to the "Diamond Paraffin
Oil," "Atlantic Red" or the "Red Insecticide Oil" are used. The
following directions for making this emulsion are copied from
U. S. Bureau of Entomology Circular 168:
"In preparing the stock mixture the soap should be put into a recep-
tacle of about 5 gallons' capacity and the oil should then be added very
slowly while the mixture is being vigorously stirred. It is important that
the oil be added in small quantities at first and also that the stirring be
sufficient to keep the oil and soap in the form of an emulsion after each
addition of oil. Thus at first about a pint of oil should be added to the
soap and the mixture stirred until no free oil appears. As the amount of
oil is increased it should always be stirred or mixed thoroly before the
next addition is made. After the required amount of oil has been added
and after free oil has ceased to appear on top of the soap, the water is
slowly poured in, about a quart at a time. To determine whether the mix-
ture will form a perfect emulsion add a little of it to soft water, and if
no oil floats, the mixture is perfect and may be used for spraying. The
presence of floating oil indicates an imperfect mixture and results from
adding the oil too suddenly or from insufficient stirring. This condition
may be remedied by the addition of more soap, which is preferable to
throwing away the entire mixture.
For spraying orange trees use 1 gallon of the stock mixture prepared
as just described to 50 gallons of water, or use the entire amount to make
200 gallons of spray material. This dilution contains approximately 1
per cent of oil, which is the maximum strength required for whiteflies
and the purple scale. For three-fourths of 1 per cent of oil add 1 gallon
of the stock mixture to 66 gallons of water, and to obtain one-half of 1
percent add 1 gallon of the stock mixture to 100 gallons of water.
Many alterations may be made in the foregoing formula. The quan-
tity of soap will depend largely upon the time consumed in adding the oil
and the amount of stirring accompanying this process. The amount of
soap is lessened if the stirring is uniform and if ample time is taken in
the preparation. Petroleum fuel oil, or crude oil, and distillate, or gas
oil, may be used instead of the paraffin oil, but in these cases a mixture
of about twice the strength will be needed to kill the insects. The amount
of water is unimportant, since the emulsion should be perfect if either i
or 4 quarts be added. The only thing to be remembered is that the di-
luted spray should contain the required percentage of oil."
The dilution recommended above (1%) is sufficient when
chiefly whitefly is to be killed, but if purple scales and particu-



Florida Agricultural Experiment Station

larly Florida red scales are very abundant Mr. Others recom-
mends 11/3 or 1 1/2% of oil. To make a 11/2% solution use
six quarts of the stock solution to 50 gallons of water.
The Boiled Formula.-The following formula is cheaper as it
requires less soap:
Soap ...........--............... .......... 2 pounds
Lubricating oil ............................--...................-. 2 gallons
Water ................ ..... ................. 1 gallon
This differs from the old formula, with four times as much
soap, in that it was intended to be heated. It is heated to the
boiling point and emulsified by forcing it twice thru a hand
pump. When ready to use, this new stock solution is to be di-
luted, as was the old. Because of its cheapness this new, heated
stock solution will probably find favor among growers who use
large quantities. When only a little is wanted, however, the
old formula will often be preferred because it does not require
This formula can be made without heat, as was first shown
by Mr. Colin MacDonald of Grand Bay, Alabama. He emulsi-
fied it by forcing it thru a pump several times.
The foregoing formulae require soft water. Hard water
must be softened before being used. Some hard waters may
be softened by carbonate of soda or caustic soda, others seem
to require soap (Dr. E. W. Berger in Ann. Rep. Fla. Agr. Exp.
Sta. 1911). Mr. Others (Fla. Grower, Oct. 27, 1917) gives
the following directions for softening even the hardest waters
from the deep wells of Florida:
Add a pound of caustic soda to 1 quart of water. Stir for one minute,
then add 100 gallons of water. Dissolve 2 pounds of soap in 1 gallon of
water and add this to the 100 gallons. Then add the oil emulsion. When
spraying use no agitator.
There are several good proprietary insecticides very similar
to the above government formulae, i. e. made from the "red"
During the past year or two there have been placed on the
market emulsions made from the so-called "white oils". They
are, of course, more expensive than the above oil emulsions
originating from less purified oils.

Fumigation has been tried repeatedly in Florida but has not
heretofore made much headway with the growers, due to sev-


Bulletin 183, Insects of a Citrus Grove

eral objections. It could be used only at night and during a
comparatively few weeks during winter. In these early experi-
ments the hydrocyanic acid gas was generated first by the old
pot method in which sodium cyanide is dropped into a pot con-
taining dilute sulphuric acid under a tent; later by a cyana-
fumer in which the gas is generated in the same manner but in
a separate machine known as a "cyanafumer" outside of the
tent. The use of liquid hydrocyanic acid has also been tried in
During the past year or two a method of fumigating citrus
trees has been used which overcomes some of the above objec-
tions. This method consists in dusting the trees with calcium
cyanide dust. This dust, when it comes in contact with moist
air or soil, liberates the hydrocyanic acid gas. This method of
fumigating trees seems to be safe over as wide a range of con-
ditions of weather as spraying. That is, it can be carried on
during any time of the year except during the rainy season
and during the early spring months when there is much new
growth and young fruit on the trees. The kills obtained by
fumigation are appreciably higher than those obtained by spray-
ing. The cost is of course greater as compared with a single
spraying. It is, however, possible that further experience with
this method will show that the reduced number of fumigations
necessary may, under at least some conditions, compensate for
the greater cost of the individual operation, particularly for
scale-insects. Where the whiteflies are the chief insects to be
controlled, fumigation would not appear practical, due to the
fact that the trees would be reinfested by the flight of the next
brood of adults and fumigation would have to be repeated. At
the time of the earlier experiments with fumigation the com-
mon whitefly was of relatively greater importance than it is
Fumigation, however, should be tried only by experienced
men. Inexperienced growers should hire it done by such men
rather than attempt to do it themselves. Furthermore, the
cost of the tents would render the method prohibitive if the
small grower had to provide his own tents. The dust ordinarily
used in fumigating trees is mixed with 15% of sulphur in order
to kill more effectively rust mites as well as scale insects and


Florida Agricultural Experiment Station

(By Dr. E. W. Berger)
It is commonplace information to those who are conversant
with this subject that insects are subject to destruction by dis-
eases as well as are larger animals and man. While bacteria
are the principal agents causing diseases in the higher animals,
certain parasitic fungi are generally the causative agents in
insect diseases. There are at least six fungous parasites known
to infect the whiteflies infesting citrus, and about as many
more on the scale-insects. On the whiteflies these are: Red
aschersonia, yellow aschersonia, brown whitefly-fungus, cinna-
mon fungus, white-fringe fungus, and occasionally a species of
Sporotrichum. All these fungi, except the Sporotrichum, grow
on, or infect, the larvae, or immature stages, of the whiteflies.
Sporotrichum, a fungus similar to the chinchbug fungus, infects
the full-grown adult whiteflies. The fungi known to infect and
destroy citrus scale-insects are: The red-headed scale-fungus,
white-headed scale-fungus, black scale-fungus, Cuban ascher-
sonia and turbinate scale-fungus.
Fungous growths consist of masses of exceedingly fine threads
that mass themselves in various ways: as fluffy, irregular
masses (molds), as cushions or pustules (the aschersonias and
brown whitefly-fungus), little stems with heads (red-headed
scale-fungus), as toadstools and mushrooms.
Fungi reproduce themselves by means of exceedingly small
bodies called spores. Those of the red aschersonia are so
small (and they vary in size) that 13,000,000 to 52,000,000 of
them could be arranged one layer thick on the surface of a
square inch.
When a spore (seed) of an insect-destroying (entomogenous)
fungus that has become lodged on or near its insect-host germi-
nates, it sends out one or several minute threads that penetrate
the body wall of the insect. Once inside the insect, these grow
and ramify into all its parts, gradually absorbing the substance
of the insect and transforming it into fungus. Sooner or later
the fungus begins to burst thru some part of the insect's skin,
wholly or partly overgrowing the insect, and forming a cushion,
a pustule, or heads on short stems, and, in turn, produces spores
(seeds). These fungi obtain their nourishment only from the
insects that they infect and not from the leaves or other parts
of the plant that the insects infest.


Insects of a Citrus Grove 357

Florida is indeed forunate that it has so many of these para-
sites to assist in the control of its insect pests. Its moist cli-
mate and abundant rainfall, together with a high temperature,
during the period of summer rains, from about June through
September, account for this fact, as fungi require these condi-
tions in order to thrive. The importance of fungi in keeping
down scale-insects, for instance, can easily be demonstrated by
spraying a tree with fungicide, such as Bordeaux mixture. This
destroys the fungi and the scales increase, a fact discovered in-
dependently by many citrus growers. Whenever it becomes
necessary to spray with Bordeaux, and scales or whiteflies are
present, this should, as a rule, be followed after some weeks
with an insecticide, as otherwise the scales or whiteflies may
so increase as to seriously injure the trees.
In setting forth the merits of the fungi, the writer does not
wish to be understood as recommending them as a panacea,
but principally as an aid in the control of scales and whiteflies.
The fungi do not thrive in all kinds of localities nor under all
conditions in which groves may be found. As previously indi-
cated, they thrive best during the period of summer rains.
Sometimes, however, favorable weather conditions prevail
earlier, as early as April, and the brown fungus thrives later in
fall than the others. The writer also once observed an unusual
development of the red-headed scale-fungus during a warm
February (Gainesville, 1909). But while these exceptional in-
stances occur, experience and observation all indicate that the
best results with fungus are in general obtained during the
period of summer rains. Neither do the fungi thrive in groves
and trees that are out of condition with perhaps only one half
to one third enough leaves upon them to conserve the moisture.
Young trees just set are poor candidates for fungus and fungus
should not be used on trees under three years old from the time
of transplanting. Unusually favorable weather conditions may,
of course, result in a fungus controlling the scales or whiteflies
in such trees, but as a more certain proposition, we recommend
spraying such trees with a spray containing oil.
The grower should not wait until his trees are loaded with
scales or whiteflies before introducing fungus or spraying with
oil sprays, etc., but should at all times know exactly the insect
condition of his trees, and use the treatment indicated for the


Bulletin 183,

Florida Agricultural Experiment Station

time and place. During the period of summer rains we recom-
mend the fungi as spraying with insecticides may be difficult
and unsatisfactory at that time on account of frequent showers.
Results from applying fungus are not immediate, but if the
application is successful some fungus will become visible in
three to six weeks, more generally in four weeks.

Any of the insect-destroying fungi listed herein can be intro-
duced by simply spraying a mixture of their spores in water
into the trees infested with the insect or insects of which the
fungus is an enemy. For insects such as whiteflies that live on
the underside of leaves, the spray must be directed against that
side. A mixture of fungus spores (the seeds of a fungus) in
water is easily made by simply mixing, stirring and rubbing
some fungus material in water and straining through coarse
cheesecloth. Approximately 100 fungus pustules, cushions or
heads may be allowed to one gallon of water. Much more or
even less may be used depending on whether plenty or but
little fungus is available. Fungus materials collected from
trees may be used, but the pure cultures when available are to
be preferred as they are perfectly free from all other fungus
spores and diseases, which may not be true of fungus taken from
trees. Cultures of the red aschersonia, yellow aschersonia and
the Cuban aschersonia are obtainable from the Plant Board.
Fungus material of fungi not obtainable in pure cultures should
preferably be collected from deciduous trees (see under each
fungus) when it is wanted for use on citrus; or vice versa.
Directions for using pure cultures of fungus are sent with
each order.
Mixtures of fungus spores and water should not be allowed
to stand in brass or copper containers for more than a few
minutes. It is better to employ only vessels and spray pumps
having but little or no brass or copper in their construction, as
some copper may become dissolved and kill the spores of the
Fungus may also be introduced by simply pinning or tying
fungus material collected from trees into other trees. Leaves
with whitefly-fungus should be pinned with the top of the
loose leaf against the bottom of the leaf on the tree. This places


Bulletin 183, Insects of a Citrus Grove

the loose leaf in its natural position so that insects may crawl
over it and scatter the fungus spores.
Scale-fungus material may also be used by cutting small
pieces of twigs and tying these onto the limbs and twigs of
the scale-infested trees. (Fig. 173.)

Since 1915 the Plant Board has been growing and furnishing
pure cultures of the red aschersonia, or red whitefly-fungus
and for several years also cultures of the yellow aschersonia,
or yellow whitefly-fungus. A
culture consists of the amount -
of fungus that can be grown in
a pint wide-mouth bottle, and
is sufficient for an acre of trees.
The Plant Board is still fur-
nishing these fungi at one dol-
lar per culture, with directions
for using them. The red ascher-
sonia will infect both the com-
mon whitefly and the cloudy-
winged whitefly. The yellow
aschersonia will thrive only on
the cloudy-winged whitefly. It
is urged that those who request
fungus send at least twenty or
thirty leaves collected at ran-
dom from their worst infested
trees for examination in order
to determine whether only one
of these fungi is required or
whether the order may be filled
Fig. 173.-A scale-fungus applied by ty-
with both kinds. ing a Piece of twig with fungus onto a
scale-infested twig.
The Cuban aschersonia is the
most recent addition to the fungi grown in pure cultures and
supplied by the Plant Board. Although but little experimental
work has been done with it, there appears to be no doubt that
it will prove a useful addition. So far it is known to infect
and destroy the pyriform scale on guava, the liriodendron scale
frequently found infesting magnolias and the banana shrub and
the soft brown scale on citrus. It has also been found infecting


Florida Agricultural Experiment Station

a soft scale on Ilex cassine and the swamp bay (Tamala pubes-
cens). The price is the same as for the other fungi. Those
who wish to try it should send plenty of scale for examination
with their request.
Remittances for fungus should be made in advance by check
or money order payable to the "State Plant Board of Florida."
(Postage stamps cannot be accepted.) Address: "Entomologi-
cal Department, State Plant Board, Gainesville, Florida." The
nominal charge of one dollar per culture, to cover actual cost of
production, is made necessary because the Plant Board has no
appropriation for this work.

Four species of aphids or plant lice are commonly met with
on citrus in Florida. They are, in the order of their im-
(1) The new citrus aphid (Aphis spiraecola Patch).
(2) The melon aphid (Aphis gossypii Glover). .


Fig. 174.-Foliage curled by the citrus aphid. (From Bul. 174.)



Bulletin 183, Insects of a Citrus Grove

(3) The brown citrus aphid or grapefruit aphid (Toxop-
tera aurantiae (Fonsc.)).
(4) The green peach aphid or the common garden aphid
(Myzus persicae Sulz.). The last three are minor pests. But, for
the past three years, and particularly during the. springs of
1924 and 1925, the first named was a pest of extremely great
importance. During the past season it has not been as severe.
These aphids can ordinarily be distinguished by their color.
The new citrus aphid is of a quite uniform light green color,
almost identical with the color of the young tender citrus leaf;
the very young ones are a trifle paler. When the wing pads
begin to form the thorax turns first a light pink color and fin-
ally, as the wings develop, dark brown, almost black. However,
the abdomen usually remains green. The melon aphid is very
variable in color but the young stages are usually a light yellow-
ish-green, much lighter than the corresponding stages of the
new citrus aphid. The older stages are usually much darker,
a dark olive green, some of them having a slate-blue cast, vary-
ing to almost black. Toxoptera aurantiae is brownish, or red-
dish brown sometimes with a purplish hue. The garden aphid
is colored much like the new citrus aphid but is much smaller.
Often a colony of aphids will consist of two or three of these
species mixed.

Aphis spiraecola Patch.
This aphid first attracted attention as a citrus pest during
the spring of 1924, altho it was not until a year later that it
was distinguished from the melon aphid. However, its pres-
ence in certain groves in the Manatee section as early as the fall
of 1922 has been quite definitely established. There is no sure
record of its presence on citrus in Florida at an earlier date.
There are many records of earlier infestations of aphids, but
usually such expressions as "the aphids left the citrus and went
to watermelons" would indicate that the species involved was
the melon aphid.
The origin of the citrus aphid is a mystery. Its native plant
is undoubtedly shrubs of the genus Spirea, of which the bridal
wreath is the species most commonly planted in Florida. The
insect is undoubtedly closely related to the apple aphis of the


Florida Agricultural Experiment Station

north (Aphis pomi) and Miss Patch, who described Aphis spi-
raecola, now regards it as identical with that species. As a cit-
rus pest in Florida it was, when first discovered, confined to
the southwestern part of the state, the center of the infestation
being in the neighborhood of Tampa. From that center it
spread during the springs of 1924-25 to the entire citrus belt
of the peninsula. It has been found also in west Florida in the
neighborhood of Pensacola. But it seems to be entirely absent
from the satsumas in the main satsuma belt, altho found on
spirea thruout the entire region. In the summer of 1925 Mr.
Others also found it in one citrus section of California, (Fla.
Ent. Vol. 9, No. 4) where apparently it had been established
for many years.
Besides spirea and citrus, it attacks the Japanese flowering
quince, haw apple, pear, the laurel cherry, and a considerable
number of herbs. Most of these are rather accidental hosts
and will be found infested only in heavily infested groves. The
sow thistle (Sonchus) and fireweed (Erechthites) are appar-
ently favorites.
During most of the year the insect breeds parthenogeneti-
cally and viviparously, that is the female is not fertilized by a
male and the young are brought forth alive. But as the cold of
the winter comes on, usually about the last of November, true
males and females are also produced. These differ markedly in
color from the parthenogenetic aphids in that they are a bright
straw yellow. These females lay eggs which in more northern
sections carry the species thruout the winter. In Florida these
eggs have never been observed to hatch, but invariably shrivel
up (A. N. Tissot). These sexual forms and eggs have never
been observed on citrus, only on spirea, the flowering quince
and other closely related shrubs.
The rate of breeding and growth depends very much upon the
temperature. Careful studies during the past year by Mr. A.
N. Tissot, Assistant Entomologist of the Experiment Station,
show that they go thru their life stages and breed most rapid-
ly during early May when it takes about six days for them to
complete their development. That is to say that six days after
birth an aphid usually begins to bring forth young. The aver-
age rate at that season is five per day. As the weather gets
warmer not only the rate of growth but the number of young


Bulletin 183, Insects of a Citrus Grove

produced per day diminishes. In June it takes eight days to
produce a generation and the average number of young pro-
duced is only two per day. This slowing up of breeding during
the summer time undoubtedly has much to do with the fact
of the insect's becoming less numerous at that season. As cool
weather approaches the growth also slows up until the average
length of a generation the latter part of November, 1925, was
ten and a half days.

In common with other aphids, the new citrus aphid is sub-
ject to the attacks of a large number of enemies which during
most of the year keep down their numbers, but have usually
been unable to do so in the spring when weather conditions are
favorable for the aphids.


Among the most important enemies of the new citrus aphid
are ladybeetles. These feed on aphids during both the mature
and immature stages. The eggs are laid among colonies of
aphids. These hatch out in from four days to a week into small,
usually hairy, larvae. These usually consume between two and
three weeks in growth and then transform into a quiescent pupa
stage. They remain in this stage for about a week and then
the mature ladybeetles emerge. The time spent in the differ-
ent stages will vary with the different species of ladybeetles,
but the above will represent an average.

Cycloneda sanguinea immaculate (Fab.)
This (Fig.
175) is the most
important lady-
beetle feeding
on the new cit-
rus aphid. It "
is common
thruout the en-
tire year. A n
adult of this
species will eat, Fig. 175.-Blood-red ladybeetle. Adult, left; pupa, center;
speces wll et ,larva, richt.


Florida Agricultural Experiment Station

on an average, sixty aphids per day, the larvae average about
sixteen per day. The larvae of these beetles are seriously at-
tacked by a fungous disease (Cladosporium) and to a lesser ex-
tent by two hymenopterous parasites, Tetrastichus blephyri and
Homolatylus terminalis.

Hippodamia convergens Guer.

This (Fig. 176) is the second most important ladybeetle
which feeds on the new citrus aphid. In late spring it ap-
proaches i n
abundance the
blood-red lady-
1 labeetle, but
d during the
winter and
early spring it
is not numer-
ous. It is pre-
Fig. 176.--Convergent ladybeetle. Larva, left; pupa, center; dominately a
adult, right.
southern spe-
cies which needs warm weather for its development. This lady-
beetle is more common on insects affecting truck crops. It is
the most common ladybeetle in colonies of the melon aphid on
cucurbits, cotton, etc. It is also the common ladybeetle on ruta-
bagas and cabbages infested with the turnip louse and cabbage
louse and on peppers and other truck crops.
The egg stage lasts from three to four days and the larval
from thirteen to sixteen, the pupa stage from four to seven
days in April and May. There is also a preoviposition period
of about eight days, making the period from one generation
to another about a month. Early in the season these stages
take longer. Each female lays about four eggs a day.
As in the case of the blood-red ladybeetle, the chief check
on the multiplication of this ladybeetle is a disease, but a
different one. This disease appears to be caused by a bacterial
organism. It is very common and destructive.
A larva of this species eats from forty to seventy aphids
per day, while an adult eats nearly ninety.


Bulletin 183, Insects of a Citrus Grove

Olla abdominalis var. sobrina Csy.
Up to the middle of April this (Fig. 177) is the second most
abundant ladybeetle in colonies of the citrus aphid. After that
date, tho it actually increases in numbers, it is forced into sec-
ond place by the rapid rise in numbers of the convergent lady-
beetle. It appears to reach its maximum about May 1 and in
June becomes
ver y scarce.
In April it
takes about t ,
four days for
the eggs to
hatch. The
larval stages
occup y 23 Fig. 177.-Two-spotted ladybeetle. Larva, left; pupa, center;
adult, right.
days, the pu-
pal, six days, and the preoviposition period about 11 days, mak-
ing the time from one generation to another about 44 days. A
larva of this species eats, on the average, about twenty aphids
per day. The larvae are very subject to a fungous disease
caused by a species of Cladosporium.
This little ladybeetle (Fig. 178) is the fourth most common
ladybeetle found feeding on the new citrus aphid. It seems to
be preeminently a summer species and by the end of June is
the most common ladybeetle in the colonies of aphids. The lar-
vae of this ge-
nus are of strik-
ing appearance
because of a
dense covering
of white hairs.
r. T The y suggest
mealybugs or
trash bugs at
first glance.
The larvae of
Fig. 178.-Scymnus terminatus. Larva, left; pupa, center;
adult, right, this species are
heavily parasitized by a wasp-like parasite, Anisostylus similis.


Florida Agricultural Experiment Station

Other ladybeetles found feeding on this aphid were Scymnus
brullei Muls; Scymnus collaris Melsh. (Fig. 179) ; Scymnus cre-
perus fraternus Lec.; Exochomus marginipennis children Muls.
(Fig. 180), a little red ladybeetle with black spots on the wing
covers; Micro-
weisia coccidi-
vora (Ashm.), a
Very small lady-
beetle with the
front part of
the wing covers
i red, the back
Fig. 179.-Scymnus collaris ladybeetle. Larva, left; pup, part and the
center; adult, right. thorax black;
Stethorus utilis (Horn), the smallest of all the ladybeetles,
scarcely larger than the head of a pin, smooth and shining
black in color;
Cerato m e-
gilla fuscilabris
f '1 o r i d a n a
(Leng.), a spot-
ted lady beetle
ally found in-
festing co 1 o-
nies of the cit- Fig. 180. -Exochomus marginipennis children. Larva, left;
rus aphid in low pupa, center; adult, right.
places. The Australian lady beetle is also found feeding on
the citrus aphid.

Leis sp.
In June 1925 the Experiment Station imported from Cali-
fornia a ladybeetle very much larger than any of our native
species. As this ladybeetle came originally from China it is re-
ferred to as the Chinese ladybeetle (Fig. 181). A larva of this
species eats an average of nearly 200 young aphids per day, and
an adult an equal number. An effort will be made to establish
this ladybeetle in Florida.
Life History.-The eggs of this species hatch during warm
weather in three days. During the winter time the average
period is five days. The larvae require 11 days to hatch. They


Bulletin 183, Insects of a Citrus Grove

remain in the pupa stage five days. Thus it is seen that dur-
ing warm weather their life cycle occupies 23 days and during
the winter time 35 days. In addition to the time spent in de-
velopment there
is a preoviposi-
tion period of 30
days. A female
lays on the aver-
age about 71
Next to the
ladybeetles, syr- b
phus fly larvae
are the most im-
portant insect
predators on aph-
ids. .In almost
any colony that
has been estab-
1 is h e d for as Fig. 181.-Chinese ladybeetle. a, eggs, b, larva, c, pupa, d,
much as a week, adnt.
one or more of these legless yellow maggots may be seen crawl-
ing about and impaling aphids on its sharp beak. These in-
sects are more abundant in the early spring. Some species
seem to disappear entirely in May. Like the larvae of the lady-
beetles, they are heavily parasitized by both vegetable parasites
(fungi and bacteria) and insects. Three wasp-like parasites
were bred out
from the syr-
phus flies dur-
ing our studies
o f the citrus
aphid in 1925.
The adults of
these larvae are
two -winged
flies. (F i g .
Fig. 182.-Syrphus fly, Baccha lugens. Left to right, adult, 182.) These
pupa, larva. flies feed on


Florida Agricultural Experiment Station

the nectar and pollen of flowers and may often be seen hover-
ing about the flowers. They have the ability to hover in front
of a flower like a humming bird without alighting on it. The
eggs are rather large for the size of the flies and glistening
white in color. They are laid among the aphids where they are
conspicuous objects.
Syrphus wiedemanni Johnson (Syrphus americana Wied.) :
This species of syrphus fly larvae became very abundant as
early as the last of January 1924. In 1925 the numbers began
to disappear in April and were entirely gone in May. One larva
of this species ate 513 aphids in ten days. Two others ate an
average of 41 and 44 aphids per day. It is thus seen that for
their size syrphus fly larvae are voracious feeders.
Allographa obliqua (Say): This is another syrphus fly
which is very abundant in the early part of the season but dis-
appears in April.
Baccha clavata Fab.: (Fig. 183.) This syrphus fly larva be-

larly abundant
late in the sea-
son, reaching its
S.iF abundance in
.:, 1 late May or
early June and
continued to be
found in colo-
nies of aphids
Fig. 183.-Syrphus fly, Baceha clavata. Left to right, adult, all Su m m e r.
pupa, larva. The larvae of
this species were much subject to a disease, apparently of bac-
terial origin.
Aphis-Lions are also important checks on the multiplication
of aphids. Descriptions and illustrations of these insects will
be found under the heading of scale-insects, page 307.

Several fungous diseases are at times very destructive to
aphids. The most common of these is caused by the fungus


Bulletin 183, Insects of a Citrus Grove

Emputsa fresenii Now. Warm, humid weather extending over
several days is very apt to start an epidemic of this disease
which may in a day or two almost totally destroy the aphids.
In 1925 this disease thoroly controlled the aphids about the 15th
of April. In 1924 it was the middle of June before a general
epidemic occurred. The disease carried off many aphids at
other times and was a very important check on their multipli-
Dr. W. A. Kuntz, of the State Plant Board, who has given
this fungus a close and exhaustive study, thus describes the ap-
pearance of infested aphids:
"First indication of the disease on the aphid attacking citrus is a slight
yellowish color over thorax and fore-abdomen with a grayish bloom. Ab-
domen very slightly swollen. (Newly molted aphids yellowish thruout.)
Hind legs somewhat raised from leaf or twig surface. Proboscis dark in
color. Elevation of abdomen becomes more evident. Death occurs. After
death yellow changes to, at first, a light brown and later to a ripe-olive
brown. The production of conidia is evident ten to eighteen hours after
death. These give to the surface of the diseased insect a tan to smoke-
colored appearance, glistening in the sunlight. Halo of spores may be
observed in moist calm weather on the leaf surface. With time the insect
becomes dark brown with tan areas, irregular, flattened and much smaller
in size."
Mr. R. L. Miller and Mr. W. L. Thompson, of the State Plant
Board, have discovered that heavy, dashing rains are very de-
structive to citrus aphids, which are washed off the plants and
pounded to death on the ground. After some heavy rains the
only live aphids which could be found were in the curled leaves
where they were protected from the rain, whereas before the
rain they had been numerous on all tender parts of the plant.


By Cultural Methods.-As the citrus aphids can live only on
young succulent foliage, except the few that may be able to find
other host plants on which they may tide over the starvation
period, they must starve to death when there is not such foliage
on the trees. Fortunately, citrus trees naturally grow in flushes
of growth alternating with periods of relative dormancy. This
is particularly true of older, bearing trees. Younger trees, par-
ticularly some varieties like Temples, are prone to a more con-
stant growth and aphids are consequently more injurious to
such trees.


Florida Agricultural Experiment Station

It should be the grower's aim to accentuate this natural
tendency of a citrus tree to grow in flushes, as it is very hard
on the aphids. The most important of the dormant periods is
that of the winter season. The most important factor in throw-
ing a tree into dormancy in the winter is undoubtedly cold and
next most important drouth. However, there are practices,
which are under the grower's control, which have a tendency to
make trees grow in the winter time. Heavy applications of ni-
trogen late in the fall may do this and should be avoided. If
trees need heavy applications of nitrogen in the fall they should
be put on in the early part, so that the trees may make a good
flush of growth and then go dormant in the winter. On the
other hand trees should not be starved. Groves in which the
trees are starved are apt to be putting out a little growth all
the time instead of growing in flushes followed by periods of
dormancy. Cultivation late in the fall should be avoided as it
has a tendency to stimulate growth. Sometimes spraying with
an oil emulsion, particularly if many of the leaves are caused
to drop, may bring out new foliage. Fall spraying should be
applied not later than October. Sickly trees which are apt to
be putting out growth at unseasonable times should be removed
from the grove.
Winter Treatment of Aphids.-During the winter the grow-
er should make an especial effort to get his grove free of aphids.
As a general thing it will be only the young trees that will need
attention at this time. Water sprouts and other sporatic shoots
appearing during the winter should be cut off so as to leave no
source of food supply for the aphids. On the other hand trees
should not be so severely pruned as to stimulate growth at that
time. Occasional colonies of aphids found in the groves should
be destroyed.
Dipping.-On young trees much of the winter growth is apt
to be out on the ends of the branches. A very thoro and cheap
method of dealing with these is to dip them in a good strong in-
secticide. A good insecticide for this purpose is a solution of
nicotine sulphate, one pound to 800 pounds of water, and about
an ounce or two of soap for each gallon of water. A compound
of derris will also make an excellent dip as it will not burn ten-
der foliage. Insecticides should be placed in a bucket so the
infested twigs can be bent over and dipped into the bucket. The
liquid will enter the curled leaves and should give 100% kill.


Bulletin 183, Insects of a Citrus Grove

Spot Dusting or Spraying.-Early in the spring when young
sprouts are apt to start out in the interior of the tree where
they cannot be dipped, spot dusting or spraying (see page 373)
should be resorted to. If dusting is to be employed it is neces-
sary that the atmosphere be perfectly quiet. Enough wind to
tell from what direction it is coming is sufficient to interfere
with dusting. The temperature should also be about 60 degrees.
The most satisfactory dust so far tried for this purpose is a 3%
nicotine sulphate-lime dust. This can be purchased already
mixed or made at home at a great saving in cost by mixing in
a barrel (Fig.
184) 33/ pounds
of 40% nicotine
sulphate and 50
pounds of hy-
drated lime. i
If growers
will free their
groves of aphids
during the win-
ter time they
will not be much
troubled with
aphids flying in
from other
groves during "
the early spring.
When new
growth is com-
ing out on the
trees so that
there is plenty Fig. 18..--A home-made mixer for mixing nicotine sulphate
of suitable food with hydrated lime.
for aphids, very few winged individuals are produced, con-
sequently there is very little migration from one grove to
another. The hardening of the foliage is the stimulus for the
production of winged individuals which may fly many miles.
Dusting.-The most thoro and usually the cheapest way of
dealing with the aphids on bearing trees during the spring
flfish of growth is to dust the grove with a nicotine sulphate-


Florida Agricultural Experiment Station

lime dust thru a power dusting machine. But to do effective
work it is absolutely essential that the atmosphere be quiet.
The cloud of dust should hover about a tree for a full minute.

Fig. 185.-Young trees tented ready for dusting.

If there is too much breeze to allow this, dusting should not be
attempted as it would be inefficient.

~~Cc~~. 1-:~~6
u h.L~u. ~ ~ l'U;

'ig. 186.- Traveling hood for power duster to make possible dusting on a windy day.


Bulletin 183, Insects of a Citrus Grove

Dusting Under Tents.-Young trees, up to a height of seven
or eight feet, can be most thoroly freed of aphids by dusting
them under a tent (Figs. 185 and 186). By using tents the
operator is independent of the wind. If the weather is warm,
70 or above under the tents, exposure of a minute will be suf-
ficient. For use under tents hydrocyanic acid gas generated
from calcium cyanide can be used instead of the nicotine sul-
phate-lime dust, but one must be sure that the trees are dry
and be careful of the dosage or burning may ensue. Hydro-
cyanic acid gas is also more apt to kill ladybeetles and syrphus
fly larvae.
Spraying.-Any good contact insecticide will kill all aphids
hit; lime-sulphur, one to 50, is fairly effective. As the com-
mon oil emulsions are apt to burn tender foliage. one must be
careful in their application. Soap and nicotine sulphate make
a most excellent spray, as also do compounds of derris. It is
not as easy to get a spray into the curled leaves as it is to get a
Whether it would be more economical to spray or dust will,
as in the case of rust mites, depend much upon the grower's
equipment, the size of his grove, the age of the trees, the dis-
tance to water, etc.
Set Out Young Trees Early.-Young trees set out late in the
winter or spring may be so severely attacked by aphids that they
will be killed outright. If possible young trees should be set
out during the early part of the winter. Our experience has
been that the first flush of growth on trees set out in Decem-
ber is not attacked by aphids. It is important to bring the
spring flush of growth out without too much damage from
aphids. Trees will then go dormant in the late spring and the
aphids will largely be starved out before the June flush of
growth starts. If the aphids prevent a tree from putting out
its full spring flush of growth, the trees instead of going dor-
mant may continue their efforts to put out new growth between
flushes and furnish the aphids with constant food supply. Or-
dinarily it is only the spring growth that will need attention.
Due to the slowing up of breeding during the summer, heavy
rains and the attacks of fungous diseases, the summer flush of
growth is ordinarily not much troubled by aphids.


Florida Agricultural Experiment Station

Aphis gossypii Glover
Next to the new citrus aphid, the melon aphid is the most
numerous one on citrus. However, it rarely becomes sufficient-
ly abundant to make control measures necessary as it is common-
ly held in check by its natural enemies. In addition to the natu-
ral enemies mentioned for the new citrus aphid, the melon aphid
is heavily parasitized by a minute wasp-like insect. This para-
site lays an egg in the aphid. From this egg a grub hatches
out which feeds on the tissues of the aphid, finally killing it.
Parasitized aphids swell up greatly until they become almost
spherical in shape. (Fig. 187.) The dead aphids turn a brassy
brown color. The grub
of the parasite after
reaching full size inside
the aphid turns into a
pupa and finally the adult
wasp emerges thru a
round hole eaten in the
top of the aphid. These
greatly swollen aphids
with round holes in their
abdomens are very com-
mon sights in a colony
of melon aphids. Altho
this parasite occasion-
ally attacks the new cit-
.rus aphid, the vast ma-
jority of the grubs fail
to emerge from the
aphid. The citrus aphid,
1 i k e-the melon aphid,
.. swells greatly and turns
a d e e p reddish brown
Fig. 187.-Parasitized bodies of Aphis gossypii color. But the grub of
the wasp nearly always dies without emerging. It is the fail-
ure of this parasite to work well in the new citrus aphid which
is the reason for the heavy infestation of this aphid.
Phyllocoptes oleivorus (Ash.)
Next to scale-insects and the citrus whitefly the rust mite
is the most expensive guest the citrus grower entertains. It is a


Bulletin 183, Insects of a Citrus Grove

sucking animal which extracts the oils from both leaves and
fruit, altho its work on the fruit attracts more attention. As a
result of this injury the rind turns a russet brown and fails
to develop normally. The rind of a russeted orange is tough and
leathery and much thinner than that of a bright fruit from the
same tree. This alone results in reducing the size of the fruit
and hence more are required to fill a box. The fruit fails to
develop properly, especially if injured early in the season, re-
sulting in a further reduction in size, and as oranges are com-
monly sold by the box, the grower loses money on small fruit.
Also a small fruit that would otherwise be marketable becomes a
cull when its size is further reduced by the mites. Altho the
quality of the interior of the fruit is not damaged and russeted
oranges are as palatable as bright ones, the market demands a
bright fruit and russets uniformly bring a lower price. The
opinion prevails in many quarters that russeted oranges are
even sweeter than bright ones. This is perhaps due mostly to
the fact that russeted fruit is not as apt to be marketed before
it is ripe.
The rust mite then attacks the pocket-book of the grower from
four directions:
1. By withdrawing oil and other juices from the leaves and
fruit it interferes with their normal growth and functions;
2. By detracting from the appearance of the fruit and low-
ering its price;
3. By reducing the size so that it requires more to fill a
box, and increasing the number of culls;
4. By delaying the coloring of the fruit so that it cannot be
marketed early.
Altho they do not show it so plainly, the leaves are really in-
jured as well as the fruit. Severely infested leaves lose their
shining appearance and take on a dry look.
Infested grapefruit sometimes develop a grayish leathery-
looking skin called "buckskin." This in its origin is perhaps
not due entirely to the rust mite. Other factors, possibly a fun-
gus, may contribute to its development. However, if the rust
mite is controlled in a grove, "buckskinning" disappears which
shows that the mites are necessary for its development.


Florida Agricultural Experiment Station

The rust mite (Fig. 188) is very small, scarcely visible to one
with the best of eyesight, but when present in large numbers is
easily recognized by one familiar with
it by the dusty or powdery appearance
of the fruit and leaves.
/.x The mite iS light yellow and wedge-
'shaped. It is broadest in front and ta-
pers uniformly to the posterior end
o where there are two small lobes, false
feet which the insect uses as an aid in
clinging and crawling. It has four short
weak legs by means of which it creeps
slowly over the leaves and fruit. When
S c full-grown it is 1/200 of an inch long.
SThe young are a little paler in color
Fig. 188--range rust mite: a, than the adults and shorter in propor-
dorsal view; b, lateral view--
enlarged, the dot in circle in- tion to their length.
dicating natural size; e, leg:
d, egg, with embryo just about LIFE HISTORY
ready to hath--more en- The eggs are large for the size of the
larged. (After Hubbard)
adult female and consequently few in
number. They hatch in four or five days in summer but during
the colder days of winter may require two weeks or more.
A week or ten days after hatching the mites molt, first resting
for a couple of days. The white skins are left clinging to the
leaf or fruit where they are largely responsible for the dusty
or mealy appearance. Shortly after the molt egg-laying be-
gins so that an entire generation may develop in a fortnight.
This rapid development enables the mites to multiply enormous-
ly in a short time if weather conditions are favorable.
The mites move about considerably. As they exhaust the oil
from one cell they move to the next. On a smooth surface,
such as an orange leaf, they can cover ten or twelve feet an hour.
In addition to traveling by their own exertions, rust mites are
often carried about by other animals. They are so small that
they can be readily transported by almost any insect as well as
by birds and man. Doubtless many are carried about by other
spiders. Such spiders as the gossamers that spin a frail web
and sail away on it with the wind may carry many rust mites
with them. Rust mites avoid both direct sunlight and dense


Bulletin 183, Insects of a Citrus Grove

shade. As a result, the shaded half of an orange growing in an
exposed situation is often russeted while the part exposed to the
sunlight remains bright. On the other hand, an orange growing
in a shaded place may be russeted on the exposed side and re-
main bright on the other. Sometimes a ring of rust is formed
around the fruit where the intensity of the light is most satis-
factory to the mites. Perhaps as a result of the aversion mites
have for dense shade, fruit grown in a low hammock where the
trees are frequently more or less shaded by other trees are less
liable to attack than fruit grown on the higher, more open lands.
For the same reason fruit produced in the interior of the tree
is not so apt to be russeted.

Mites multiply most rapidly during dry weather. So it is
during dry weather or immediately following drouths that an
especially vigilant watch should be kept for rust mites. The
month of June is, if a number of years be averaged, most likely
to bring a heavy infestation. But the mites are liable to cause
damage during any month of the year. A number of predators
feed on rust mites, syrphus flies and predaceaus thrips (Aleuro-
dothrips fasciapennis) being among the most important. How-
ever, they cannot be depended upon to control the mites.
Mr. W. W. Others has recently shown (The Florida Bug-
gist, Vol. I, No. 3) that a sudden severe cold spell is very fatal
to mites, not only the adults and young being killed but the
eggs also are destroyed.
The efficient control of rust mites calls for constant vigilance.
Because of their small size they are difficult to detect even by
one with good eyesight. The citrus grower should provide him-
self with a good hand lens that will magnify fifteen or twenty
diameters, and carry this constantly in the grove. With this he
should examine his fruit every few days, especially any tree
that has a dry, dusty or powdery appearance. Old fruit hang-
ing to the tree, such as the "June bloom" of the previous year,
is most likely to be infested and should receive special attention.
If control be delayed until the rust appears on the fruit it will be
too late, as enough damage will have been done to prevent the
fruit from being graded as "brights." Fruit once russeted will


Florida Agricultural Experiment Station

never be bright again altho the rust may become a little less
noticeable as the fruit colors up. The grower who has permit-
ted his fruit to become russeted can, and of course, should, pre-
vent further damage by promptly spraying, provided the mites
are still present.
The only way to be sure of having bright fruit is to watch
it constantly and as soon as the rust mites are noticed apply the
spray. The grower should have his spraying machine always
in working order and a supply of insecticides always at hand so
there will be no delay when the mites are first noticed.
Because of the difficulty of seeing the rust mites, and the
rapidity with which they multiply, some growers make a prac-
tice of spraying their trees every month or six weeks as a
precautionary measure. Altho this practice is undoubtedly pref-
erable to neglect or carelessness in respect to rust mites, it will
lead to unnecessary expense in spraying. It may be justifiable
when necessary to leave the grove in the hands of a foreman
who is incompetent to notice the first signs of increase in the
number of mites.
Like all members of the spider class, rust mites are very
sensitive to sulphur. Sulphur does not kill the eggs but, as it
remains active on the trees for several days, it kills the young
mites as they hatch. It is not necessary that the mite be actually
hit by the sulphur; the sulphur slowly oxidizes on the tree and
will kill all mites within a radius of a small fraction of an inch.
It is thus a sort of fumigation process.
One may use either free sulphur, or some of its compounds,
applying it dry, or in the form of a spray. Free sulphur is one
of the best remedies against red spiders, or mites. It is some-
what slower in its action than some compounds of sulphur, often
taking two or three days or more to do its work, but it remains
active for a long time, frequently two or three weeks, and usually
kills the mites.
Sulphur may be applied as either a spray or a dust. Which-
ever the grower should use is largely a matter of cost and will
depend much upon his equipment, size of the grove, handiness
to water, etc. Dusting is much more rapid than spraying. A
grove can be dusted in from one-fourth to one-tenth the time it


Bulletin 183, Insects of a Citrus Grove

takes to spray it, depending much upon the distance necessary
to haul the water, etc. The cost is less. In dry, warm weather
dusting is fully as effective as spraying, but if the weather is
cool or the dusting is followed by a heavy rain within a day or
two after application, spraying will usually give better control.
Growers with large groves will find dusting more economical
than spraying. But small growers may well hesitate about go-
ing to the extra expense of buying a dusting machine. Growers
must have a sprayer to control scale-insects and whiteflies and,
if the grove is not too large, it will be more economical to use
the same spray outfit for controlling rust mites than to tie up
a considerable sum of money in the dusting machine.
The greatest advantage of dusting over spraying is the ra-
pidity with which it can be accomplished. Rust mites multiply
very rapidly if the weather conditions are favorable and if it
takes as much as a week for a grower to cover his grove with
a spray machine the rust mites may have done much damage
before he completes the operation, even tho he begins to spray
promptly upon the appearance of the rust mites. A dusting
machine may also be found very useful in the control of aphids.
Small growers with young trees, up to a height of twelve feet
or so, can get along fairly well with a hand duster, costing from
$15 to $25. Those of the bellows type are more suitable for this
work than those of the fan type as they throw the dust some-
what higher.
For dusting one may use simply the finely ground flowers of
sulphur. The more finely ground the more readily it goes thru
the dusting machine, but some of the finely ground sulphurs
cost appreciably more. Commercial makers of sulphur dusts
frequently add about 15% of hydrated lime to the product.
This makes it go thru some of the dusting machines more read-
ily than the pure sulphur.
Sulphur works better when the nights are moist and the days
bright and sunny, as under these conditions the decomposition
takes place more rapidly.
Many growers make the mistake of applying too little sul-
phur to their trees and consequently getting a poor control. A
good sized bearing tree will require, according to size, from a
quarter to half a pound of sulphur dust. If there is much wind
blowing, even more will be required to give a good covering.


Florida Agricultural Experiment Station

Lime-sulphur is the spray solution commonly used for rust
mites. Use about 1 gallon to from 50 to 65 gallons of water.
The grower can make his own lime-sulphur by boiling lime and
sulphur together over a fire, but this does not ordinarily pro-
duce as good a compound as the commercial product which is
made in large quantities and boiled with live steam. There are
several insecticide houses making the substance in the State.
This reduces the cost appreciably as lime-sulphur is rather
bulky and the freight becomes a considerable proportion of the
cost on long hauls. The product, especially the home made, is
liable to vary considerably in its strength and should be tested
with a Baume hydrometer before being used. The hydrometer
costs but a dollar or two and with care should last for years.
If the product tests 32 degrees, which is standard, 1 gallon to
65 of water is sufficient. If the reading is lower more should
be used. The following table gives the number of gallons of
water to use with a gallon of the lime-sulphur at any degree of
concentration likely to be encountered. For convenient refer-
ence there has also been included the amount to use as a winter
wash to kill San Jose scale on either trifoliata or peaches or
plums and also the amount to use as a fungicide on citrus during
the summer.

TABLE 1.-Dilution Table for Lime-Sulphur Solution
Baume Number of gallons of water to one gallon of lime-sulphur
reading For a winter wash As a fungicide For rust mite
36 9% 34 82
35 9 33% 79
34 8% 32 76
33 8%1 31 73
32 8 30 70
31 7% 29 67
30 71% 28 64
29 7 27 61%
28 6% 26 57%
27 61 24% 54%
26 6 23% 51
25 5 221 48%
24 514 21 45%
23 5 19 42%
22 4% 18% 39 2/3
21 41/ 17% 36%
20 4 17 34
19 3% 16% 31%
18 31 1514 29%
17 3% 14% 27%
16 3 13% 25%
15 2% 12% 24


Bulletin 183, Insects of a Citrus Grove

Aside from its insecticidal value, lime-sulphur seems to act
as a stimulant to the fruit, increasing its size and causing it to
ripen earlier.
The oil emulsions also kill all rust mites struck, but do not
harm those which only get close to it, as does the lime-sulphur.
A commercial product, "soluble sulphur" or soda-sulphur, is
sometimes added to the oil emulsions to make them more effective
against rust mite. Either of these compounds is often used alone
in place of the lime-sulphur.
The soda-sulphur stock solution is:
Flowers of sulphur.........................30 pounds
Caustic soda .................. .....................20 pounds
W ater .....................................................20 gallons
This should test about 16 degrees Baume. When ready to
use take 1 part of the solution to 40 of water. When used alone
it is not as effective as the lime-sulphur solution.
Some of the proprietary oil emulsions on the market are made
with the idea of combining them with lime-sulphur, others are
not. The grower should be sure of his oil emulsion before he
combines it with lime-sulphur.

Tetranychus spp.
Two species of spider mites infest citrus in Florida. One, the
six-spotted mite, is pale grayish-yellow with six dark spots ar-
ranged in two rows on the back. Some growers restrict the
name "red spider" to this species. Others use it, as here, to
include both species.
Both are sucking pests which withdraw sap from the leaves
and, like the rust mite, are most troublesome in dry weather.
They are preyed upon by many insects and larger spiders. Both
the larvae and the adults of ladybeetles and the larvae of lace-
wing flies feed upon them altho they prefer other food, espe-
cially aphids. Aleurodothrips also feed upon them.
Control in each case is the same as for the rust mite, but
they are not killed as readily by sulphur dust during cool
T. sexmaculatus Riley
The six-spotted mites attack the under side of the leaves
where they spin thin, tent-like webs under which they stay. As
a result of their sucking the leaves turn yellow in the spots under


Florida Agricultural Experiment Station

the web. These spots increase in size as more sap is withdrawn
until finally the whole leaf becomes yellow, curls, and falls. If
many of the leaves are lost the fruit also falls from the devitalized
trees and the financial loss occasioned thereby is direct and se-
vere. The young show few or none of the spots which are char-
acteristic of the adults.

T. citri McGregor
The purple mite, which is much less destructive than the six-
spotted mite, is found on both sides of the leaves and on the fruit.
The affected parts take on a gray, dry appearance, quite different
from the yellow spots caused by the six-spotted mite.
This mite is much more abundant on satsumas in the western
part of the state than on round oranges in the peninsula. 'It is
also common on citrus trifoliata.
The reddish-yellow eggs, besides being glued to the leaves, are
held by a series of silken threads arranged in a peculiar and
characteristic fashion. A silken stalk arises perpendicularly
from the upper side of the egg and to the top of this stalk are
fastened fourteen threads of silk which run out in as many di-
rections, like guy ropes of a derrick, and are fastened to the
surface of the leaf.
The eggs hatch in a week or two and the young require about
twelve days for growth. During this period they molt three
times. The very young larvae have, like insects, six legs, but
after the first molt there are eight, the typical number of the
spider class. The female lives for about a month after becoming
an adult, during which time she lays from thirty to seventy-five
Frankliniella tritici bispinosus Morgan
The Florida flower thrips (Fig. 189) is a minute, soft-bodied
insect about a twenty-fifth of an inch long and is very common
in many flowers, including citrus blossoms. Its color varies
from yellow to orange. The abdomen is commonly lighter col-
ored than the thorax. When the insect is disturbed it curls its
abdomen up over its back as if ready to sting. The insect is
harmless to man, altho on the tenderer parts of the skin it is



Bulletin 183, Insects of a Citrus Grove

capable of causing some slight pain with its mouth parts.
Under a lens it is seen to have brownish-red eyes and eight-
jointed antennae. There are four wings. These are thin and
membraneous and fringed with relatively long hairs. The

Fig. 189.-Florida flower thrips: Adult female. Highly magnified. (Drawing by Dozier.)

young are very similar to the adults but lack the wings, and
are lighter in color.
Thrips may inflict two types of damage to the crop: (1)
Shorten the crop by causing an excessive dropping of the bloom
and young fruit, and (2) lower the grade of the fruit by scarring
it and making it unattractive in appearance.
Thrips are sucking insects but their punctures are shallow,
very numerous, and close together so that the attacked tissue has
the appearance of having been rasped away. The area attacked
loses its color and becomes sunken.
In the orange and grapefruit bloom the favorite feeding place
is on the inside of the cylindrical column of stamens. Next, the
succulent petals are chosen. A limited amount of feeding on
these evanescent organs probably does little harm, but if the
insects are abundant the tissue of the receptacle about the base
of the ovary is attacked, and then the ovary itself. It is in the


Florida Agricultural Experiment Station

receptacle also that most of the eggs are laid and here the lar-
vae of the next generation can be found feeding after both sta-
mens and petals have fallen and most of the adult insects have
flown to more inviting fields. If sufficiently injured, this re-
ceptacle turns yellow and finally causes the young fruit to drop.
As the orange tree generally produces an abundant bloom,
much of which will necessarily drop, the actual amount of dam-

Fig. 190.-Thrips marks on grapefruit.

age the insects do to the setting of the fruit may, if the bloom
is heavy, be small. The results of several years of experimen-
tation with this insect indicate that on trees which have a
heavy bloom and a moderate number of thrips, or even a heavy
infestation of thrips, if the bloom also is very heavy, thrips
do little harm. The writer has observed that many groves set
a big crop of fruit in spite of a moderately heavy infestation of


Bulletin 183, Insects of a Citrus Grove

thrips. However, our experiments show that if the bloom is
moderate or scanty and thrips unusually abundant they may
seriously shorten the crop. On some trees this reduction was
as great as two-thirds as compared with sprayed trees.
The feeding of the thrips on the ovary of the blossoms or the
young fruit causes smooth, brownish, sunken areas in the shape
of streaks and blotches, and often circles about the fruit. (Fig.
190.) These sunken areas have a thinner skin than the remain-
der of the fruit and are more liable to attacks of fungi and
insects, such as the pumpkin bug, than is the healthy skin. This
damage is usually done when the fruit is less than three weeks
old. It is mostly the work of the young thrips that hatch out
in the receptacle at the base of the fruit after the petals and
stamens have fallen. These young crawl onto the fruit and feed
there until they acquire wings, when they fly away. Few adults
are ever found on the fruit after the petals and stamens have
In one grove in which a rather careful estimate was made
23 percent of the fruit was sufficiently scarred to lower its
grade in the hands of a careful grader, and four percent was
counted as culls. This is the greatest amount of damage noted.
It will usually not exceed five to ten percent of the fruit even
in a grove where thrips have been abundant.
The eggs are laid mostly in the enlargement of the stem (re-
ceptacle) at the base of the blossom. They are placed just under
the epidermis in a shallow slit made by the saw-like ovipositor
of the female. They hatch in two to four days, three days being
the average time required. The larval stage is of ten to twenty-
four days' duration, averaging fifteen days. The last two days
are spent as pupae. Altho capable of moving during this stage
the insect feeds virtually not at all. The wings show as short
pads on the back. The adult female begins to lay eggs freely
when about five days old. It is seen that the entire life history
thus requires about twenty-three days. This is true only during
the warmer part of the year. During the winter, development is
much slower and reproduction ceases altogether in the coldest
weather. While some breeding usually goes on in every winter
month it is limited to the warmer periods. During the coldest



386 Florida Agricultural Experiment Station

weather thrips lie inactive in the depths of flowers. There are
probably a dozen generations in the course of a year.
In breeding cages the adults have lived for eight weeks in
winter and for four weeks in March. Out of doors, under natural
conditions, they may probably live longer.

Apparently, very few insects or other animals feed upon
thrips; their very insignificance protects them. Neither do they
seem to be much parasitized by entomogenous fungi.
Inclement weather is by all odds the most efficient agency in
checking multiplication. A heavy dashing rain has frequently
been observed to nearly exterminate them, only a small fraction
of one percent surviving. The rain knocks them from the flowers
and pounds them to death on the ground.

As previously stated our present information would indicate
that thrips are usually only a minor pest of citrus. Only when
abundant, at least a dozen per blossom as an average, will it
pay to spray for them. Yet the past several seasons' work of
the Station would indicate rather clearly that in case of a heavy
infestation of thrips, even in a grove with abundant bloom,
spraying even once will increase the amount of fruit set from
three to eight percent. On a few trees with scanty bloom and
abundant thrips it has increased the amount three hundred
percent. On the average the proportion of scarred fruit was
reduced about fifty percent by one spraying.
The first spraying should be given when the trees are in full
bloom and the nozzle should be pointed straight into the blos-
soms. Some dropping will result from this spraying but it will
consist entirely of fruits that would have dropped later if no
spraying had been done. A week or ten days afterward, if -there
are still many thrips in the later bloom or on the young fruit, a
second spraying may be given.
In view of the effect of dashing rains on thrips, the importance
of using strong pressure is evident. Indeed, water alone does
much good if driven at a pressure of at least 200 pounds. A
spray gun does better work than a rod and nozzle. However,
to do effective work, an insecticide is necessary. Tobacco is

Bulletin 183, Insects of a Citrus Grove

very efficient and a little soap or lime-sulphur to give it body
increases the effectiveness of the spray. The following, first used
against a closely related thrips in the orange groves of Califor-
nia, has given the best results in Florida:
Commercial lime-sulphur solution, 32 degrees Baume................2 2/3 quarts
Nicotine sulphate ..... ............................-. .....-% pint
W after ........................... ...... .................................50 gallons
Some growers spray lime-sulphur into the bloom to control
scab, using it at a strength of 1 part to about 40 of water. In
that case it is necessary only to add the 31/2 ounces of nicotine
sulphate to the lime-sulphur solution. Some growers have re-
ported damage from the use of lime-sulphur at this strength.


There are a number of large plant-bugs which attack almost
any succulent plant and at times become very annoying pests.
On citrus they inflict two kinds of injury. They suck the sap
from the young and tender twigs, often causing them to wilt and
finally die. It is only on young trees that this type of injury
is worthy of attention. A habit fraught with much more danger
to the financial interests of the grower is that of attacking the
ripening fruit in the fall. From this the bugs sometimes extract
so much juice that the fruit drops. Sometimes as much as half
of the crop is lost in this manner. Even if the fruit clings to the
tree the punctures made by the bugs give to fungi and other
organisms that cause decay an avenue of entry into the fruit.
Naturally those varieties of citrus that have thin skins suffer
most. Tangerines, including satsumas, are the first choice of
the bugs, and oranges second. Grapefruit is not much troubled.

Nezara viridula Linn.
The pumpkin bug or green stink bug is by far the most
common and destructive of the large plant bugs. It breeds
particularly on- such legumes as cowpeas and beggar-weed and
when these are grown as a summer cover crop in the groves and
allowed to stand too long, the bugs may attack the fruit. The
color of this bug is usually bright green, but some of the bugs,
especially hibernating ones, are dark olive-green or pinkish in
color. The females are a little more than a half inch long and
slightly more than half as wide, being broadly oval in outline.


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