|UFDC Home||| Help ||
|Table of Contents|
|Florida flower thrips|
|Large plant bugs|
|Minor pests of the fruit|
|Borers of trunk and limbs|
|Bark and leaf scavengers|
|Minor pests of young trees|
|Other pests of young trees|
|Allies of the citrus grower|
|Trees that harbor citrus insec...|
CITATION SEARCH THUMBNAILS PAGE IMAGE ZOOMABLE
STANDARD VIEW MARC VIEW
|Table of Contents|
Table of Contents
Florida flower thrips
Large plant bugs
Minor pests of the fruit
Borers of trunk and limbs
Bark and leaf scavengers
Minor pests of young trees
Other pests of young trees
Allies of the citrus grower
Trees that harbor citrus insects
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
bJletin 88 April, 1937
(A revision of Bulletin 67)
COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service
University of Florida, State College for Women
And United States Department of Agriculture
Wilmon Newell, Director
CITRUS INSECTS AND
J. R. WATSON, Entomologist
Florida Agricultural Experiment Station
E. W. BERGER, Entomologist
State Plant Board of Florida
Bulletins will be sent free to Florida residents upon application to the
AGRICULTURAL EXTENSION SERVICE
BOARD OF CONTROL
GEO. H. BALDWIN, Chairman, Jacksonville
OLIVER J. SEMMES, Pensacola
HARRY C. DUNCAN, Tavares
THOMAS W. BRYANT, Lakeland
R. P. TERRY, Miami
J. T. DIAMOND, Secretary, Tallahassee
STAFF, AGRICULTURAL EXTENSION SERVICE
JOHN J. TIGERT, M.A., LL.D., President of the University
WILMON NEWELL, D.Sc., Director
A. P. SPENCER, M.S., Vice-Director and County Agent Leader
J. FRANCIS COOPER, M.S.A., Editor
JEFFERSON THOMAS, Assistant Editor
CLYDE BEALE, A.B., Assistant Editor
E. F. STANTON, Supervisor, Egg-Laying Contest
RUBY NEWHALL, Administrative Manager
COOPERATIVE AGRICULTURAL DEMONSTRATION WORK
W. T. NETTLES, B.S., District Agent
H. G. CLAYTON, M.S.A., District Agent, Organization and Outlook Specialist
J. LEE SMITH, District Agent and Agronomist
R. S. DENNIS, B.S.A., Assistant District Agent
A. E. DUNSCOMBE, M.S., Assistant District Agent
R. W. BLACKLOCK, A.B., Boys' Club Agent
E. F. DEBUSK, B.S., Citriculturist
A. L. SHEALY, D.V.M., Animal Industrialist2
HAMLIN L. BROWN, B.S., Dairyman
N. R. MERRHOF, M.AGR., Poultryman2
D. F. SOWELL, M.S., Assistant Poultryman
WALTER J. SHEELY, B.S., Agent in Animal Husbandry
C. V. NOBLE, PH.D., Agricultural Economist2
FRANK W. BRUMLEY, PH.D., Agricultural Economist, Farm Management
R. H. HOWARD, M.S.A., Asst. Agr. Economist, Farm Management
GRAY MILEY, B.S.A., Asst. Agr. Economist, Farm Management
D. E. TIMMONS, M.S.A., Agricultural Economist, Marketing
R. V. ALLISON, PH.D., Soil Conservationist2
A. E. MERCKER, Field Agent, Cooperative Interstate Marketing1
COOPERATIVE HOME DEMONSTRATION WORK
MARY E. KEOWN, M.S., State Agent
LUCY BELLE SETTLE, M.A., District Agent
RUBY MCDAVID, District Agent
ANNA MAE SIKES, B.S., Nutritionist
VIRGINIA P. MOORE, Home Improvement Agent
ISABELLE S. THURSBY, Economist in Food Conservation
CLARINE BELCHER, M.S., Clothing Specialist
NEGRO EXTENSION WORK
A. A. TURNER, Local District Agent
BEULAH SHUTE, Local District Agent
1 In cooperation with U. S. D. A.
INJURIOUS INSECTS ..... ...... ................. ... ......... 5
Scale-Insects ..................... ................. .... ........ ...... ................. .. 6
A rm ored Scales ...................................... ... ... ...... ........... ........ ... 7
Purple Scale .................................. .....--- ...................... ......... .. 9
Natural checks ........................- ......-..- ......... .....----------.............. 13
Entomogenous Fungi ....--.......-........-....--... .....--------........-- .--... 13
Predaceous Insects .........--.. ........---- ..... ..--......----------......... 16
Control --..-.........-.........-- ----.-- ...- .-------................... -.-- 20
Long Scale ......--------......-- ....-- .. ----.......--..........- ... ....-..--- ......- ..... 21
Florida Red or Round Scale ................... ................................ ... 22
Minor Armored Scales.-----...........---- ................................. 24
California Red Scale ...........................----....-- ..- ..... ......... 24
Dictyospermum Scale ......................---- ...... ....----...-..--- ...--- .. 25
Rufous or W est Indian Scale........-...---- .......................... ............... 25
Camphor Scale ..............-- ---...... .... .... .....................- .......- 25
San Jose Scale .......... ......... .................................. .............................. 26
Chaff Scale ........................................ -- ...................... ........... 26
Citrus Snow Scale ................................... ................................... ... 28
Soft Scales .......................................----..----..... .......... ......... 28
Soft Brown or Turtle Back Scale...................... ............................. 29
Hem ispherical Scale ............. ............... ...................................... 30
Black Scale ..--...............-----...- --............--............... .......... 31
W ax Scales ...... ............................. ...................... 31
Florida Wax Scale ..............---............. ------- ..................... 31
Barnacle Scale ......----........................---- .... ....-- ....---- ....--. 33
Japanese or Mexican Wax Scale--............... .........................- 33
Pyriform Scale ............................ .-- -. ............... -.... ... .--.........- .. 34
Green Shield Scale .................................................... ....... ..... ..-- 35
Entomogenous Fungi of Soft Scales-.--...... ..............---------............ 35
MEALYBUGS ...--..----...... -----.--- ------.....-....--.-..........................-.-- 37
Common, or Citrus, Mealybug................--.......---------...........---- .. -- 38
Long-Tailed Mealybug ..............--.............-- .........---......---- ---- ..--- 41
Cottony-Cushion Scale .............................. ---------............-- ..--- 41
Vedalia or Australian Ladybeetle-..---.........................--.............. 43
W HITEFLIES .....................................................--.....-- ...--- ...................... ........ 45
Common, or Citrus, Whitefly .............--........- .... ............-......... 47
Food Plants ....--....-----.........----......-- ..----... ----......-....-- ........--- 48
Cloudy-Winged Whitefly ..........................................---..-----.....--.. 50
W oolly W hitefly ............................-- .......-----.... ..-..--- ..- ..-- ...- --........ 53
Flocculent W hitefly .........-- ...................-- .... ..---- ...---- ---....-- ........ 55
Florida, or Guava, Whitefly ....................-.......----.......-... .. .---- 55
Bay W hitefly ...................----.......... ........- ...............- -- .............. 56
Inconspicuous, or Sweet Pootato, Whitefly .......--....................--- ......... 56
Mulberry Whitefly ................. .................... .... .---- --- ........-.... 56
Blackfly ......-..-..........-- -........................... ...-----..........--- ....------............ 56
W hitefly Fungi .................. --................................... -------- 57
Control of Whiteflies and Scale-Insects..---.......---............--.....---. 60
Spraying ..... .............................. ...... .......--.--- ........-------..... 60
Fumigation .................-................. -----... ---------............-... 64
By Fungus Parasites ............. ..... ........--.........- .......---- ... 64
APHIDS ................................................... .....--- ......-....--------- 68
The Green Citrus Aphid .............................. .....---- ..---- ...... ... 69
Enem ies .............................................------.. ........... 70
Ladybeetles .......-...--------............... ...-- ---.. -------- 71
Syrphus Flies ......................................--- ......----- -- 75
Aphis-Lions ............................... ... .......----- ..- ......-...... -- ----- -- 76
Fungus Diseases .....- .........--.........----...... ...-------. 76
Control .........................-.-- ....... -..---------........... ..... 77
The Melon Aphid ...---..............- ... .......... --- --.-----. 82
RUST M ITE .--........-----.............................- .----. .. ........................ 83
RED SPIDERS ....--- ..--------..................... ..................................-------------... ...... 89
Six-Spotted M ite ........-------........... .. .......................................... 89
Purple M ite ......................... .......................... ............................. ............ 90
FLORIDA FLOWER THRIPS ..... ..........................................................---... 90
LARGE PLANT BUGS .................................................................................... ..... 95
Southern Green Stink-Bug or Pumpkin Bug-...........-- .........-- ------... ....... 95
Other Plant Bugs .................... ..........-- ............. ... ......--- -- ..... 101
Cotton Stainer .......................... -- ............. .. .............................. 101
M INOR PESTS OF THE FRUIT...........................------........................... .................. 102
Orange Totricid ................... .........------ ................ .............. 102
Grasshoppers and Katydids ........................... ............- -..................... 103
Bagw orm s ........................................------...................... .- .............-...-............ 104
R odents ........................................................................- ................................... 105
Mediterranean Fruit Fly ..--.....----...-............-- ............-............................. -105
Morelos Fruit Fly .................................... -----------........... .............. 106
Scavengers ......................................-------.....-----..... -----....................... 106
BORERS OF TRUNK AND LIMBS ..... ----....... ................... ................................... 107
Orange Sawyer ---...--.. ---------..........-.......... --.. ....---..----....................... 107
Shot-Hole Borers, or Pin-Head Borers..........---...-- .................. ... .... 107
Tineid M iner .... --- --.......... .. ----........... ......... ......... .. ................ 108
BARK AND LEAF SCAVENGERS .............. ---..........-------....................... 108
Psocids ........................................ ........... ....--------- ..------ ---..... 108
Hymenorus Obscurus -....----.....--.. -----............. --- ....-------.---. 109
MINOR PESTS OF YOUNG TREES .........-.................................... 109
LEAF EATERS .................. .---- ... ..--.. .......---- .....-----. .-----..- .... 110
Orange Dog ............................... .......------- ...... ....- ......---- 110
Slug Caterpillars ---------..... ----..---.-----......---- ..------ 112
Puss Moth ................ --------..----................. --..--- .--- .. 112
Saddle-Back .........-- .... ------------.......-- ........-..--...-... 113
Hag M oth .................----------.... ... ............... .......... 113
Grasshoppers .............------ ........------....--.--........- --... 114
Katydids .....................--------...... ....................--.--- ..---- ..----- 116
Citrus Root-Weevil --.......--.. ----------.. ..--... ---.................------- .---- 117
June Bugs ... --- -----...........--............. .----..............----- 117
Prickly-Ash Beetle ....------...... ..............--.---..--- ................. ------118
Striped Cucumber Beetle .........-----............... -----------................. ....... 118
OTHER PESTS OF YOUNG TREES.. -............--...-------........................ 119
Sharp-Shooter, or Orange Jassid-....--------------..................------. 119
Ants ...... .------ ............--............................ ...... ..................-- 119
Termites, "White Ants", or "Wood Lice"...- ................................... 121
Salamanders and Gophers ................. --..................... ......------. 122
Millipeds ....-----.......-...-................... ......... ...--.......... .------- ....... 125
ALLIES OF THE CITRUS GROWER.........--......-----------.-.------ ...... 125
Birds ----.......................... .----....-...---. ..... ------..............----. 125
Other Vertebrates ....... ...-----------....... ---- -----.................. 126
Predaceous Bugs ........--.. ---- .....-----..----.-- ..----- 126
W asps .....---------.. ..-......-..................- ----- -... .................... 126
Parasitic Flies ...........-..... .--. -. -----.............. -- ---................... 127
TREES THAT HARBOR CITRUS INSECTS...............-- --......----------------- 127
ACKNOWLEDGMENTS ....... ---- ---------------..... -----.. ........ 127
LITERATURE CITED ................-.......---------........-. 128
CITRUS INSECTS AND
By J. R. WATSON AND E. W. BERGER
The aim of this bulletin is to discuss briefly the most com-
mon insects found in Florida citrus groves-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 writers have selected chiefly those insects which have been
the source of much correspondence with citrus growers. Neither
has any attempt been made to present an exhaustive account of
the more important pests, nor to repeat data that are easily ac-
cessible to the average grower through 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 smaller forms and early stages of most insects,
a good hand lens is necessary. A satisfactory one, magnifying
15 or 16 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.
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 order of importance:
1. Purple scale
2. Rust mite
3. Common citrus whitefly
4. Florida red scale
5. The green citrus aphid
6. Cloudy-winged whitefly.
6 Florida Cooperative Extension
There is, however, a larger number of pests which should be
watched, and against which the grower should take measures
during occasional years. They are, again approximately in the
order of their importance:
7. Red spiders
9. Long scale
11. Pumpkin bugs and other plant bugs
12. Cottony-cushion scale
13. Citrus snow scale
14. Orange dog
15. Chaff scale
18. Gophers and salamanders.
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 are usually flat and are closely attached to the
surface of the host plant like a scale. They are bugs and,
therefore, sucking insects, although very degenerate in struc-
ture. While most insects go through four stages during their
development (egg, nymph or larva, pupa and adult) this is true
of only the males of scale-insects. Females virtually omit the
last two stages. They acquire mature sexual organs and re-
produce while still retaining the larval form. Even in the male
the adult life is extremely brief, lasting for but a day or two.
Citrus Insects and Their Control 7
As the adult males are very small and inconspicuous, gnat-like
creatures, the orange grower seldom notices them. They have
only two wings. Having no mouth parts or digestive organs,
they can take no food during their adult life. Their only activ-
ities consist in finding and fertilizing the females.
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,
horny substance between which the insect lives, much as an
oyster in its shell, although not attached to the plates by muscles.
The 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
after 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 usually is 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. The larva
usually can move about until egg laying time, but it moves very
slowly. Insects of this group are called soft scales (Coccinae).
In the third group, mealybugs and their relatives (Dactylo-
pinae), no hard coating is formed but the body usually is cov-
ered with flaked wax which gives a mealy appearance. They
usually retain their legs and are capable of moving about
In the armored scale group the eggs usually 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
8 Florida .Cooperative Extension
eggs hatch under this protective covering which shelters them
not only from rain and cold but also from other insects which
might 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. Having found it,
they insert their beaks composed of four slender threads, and,
if they are destined to become females, never move about again.
They at once begin to secrete threads of wax which form a cov-
ering 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 later a second
molt takes place. This time, however, the molted skin is re-
tained and incorporated with the new portion of the scale
where usually it is quite conspicuous. (Fig. 1.) It is situated
near the middle or the front end of the mature scale and often
differs a little in color from
the remainder. At this point
N in the life history a difference
between the males and fe-
S males begins to be noticeable.
,'- The males grow no more but
molt again and pass into the
pupal stage from which the
A R adult two-winged fly-like cre-
Fig. 1-A-Scale of female with exuviae atures emerge in about a
central: a, first exuvia; b, second exuvia;
c, secretionary covering. B-Scale of female week.
with exuviae terminal: d, first exuvia; e, sec-
ond exuvia; f, secretionary covering. (After The female is fertilized
Merrill and Chaffin, 171.)
shortly after the second molt
and does not molt again, although she continues to increase in
size. As a result of this growth after the second molt, female
scales are much larger than males and live longer. Males go
through this molt at an age earlier by about a week than females.
The third and fourth molts are then passed quickly so that by
the time the females are through with their second molt and
are ready to breed, the males have become winged adults and
quickly find the females. The armored scales produce very little
Iltalic figures in parentheses refer to "Literature Cited" in the back
of this bulletin.
Citrus Insects and Their Control 9
Lepidosaphes beckii (Newm.)
The purple scale is the most destructive insect in Florida
citrus groves. The mature scale (Figs. 2 and 3) is shaped
somewhat like an oyster shell. It is purplish-brown in color
and 1/s inch in length. It is found on the twigs and fruit as
Fig. 2.-Purple scale on grapefruit, showing reaction to light. The clear spot in the
center was in contact with another fruit.
well as on the leaves. However, it is not abundant on the trunk
or larger branches except on young trees. On the leaves it
collects 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.
Although the effect of scattered individuals is not externally
apparent, they check the growth of the infested part and inter-
fere with its functions. If sufficiently abundant in one place
10 Florida Cooperative Extension
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. 3.-Purple scale following woolly whitefly. (After Watson, 29.)
Besides this direct injury the punctures of scale-insects af-
ford avenues of entry for certain fungus diseases of the fruit,
such as stem-end rot.
The eggs are laid under the scale of the mature female. They
hatch in from 15 to 20 days. The young crawlers remain 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 avoid both deep
shade and direct sunlight 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. 2.) 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. 3.) Probably for this reason scale-insects usually are
more severe along a road than in other parts of the grove. The
dust particles settling on the leaves provide the crawlers with
Citrus Insects and Their Control 11
partial shade and protection. An unusually favorable place for
the development of the scale crawlers is in leaves curled by the
green citrus aphid. Scales in these curled leaves are very diffi-
cult 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
negative geotropism, a movement opposite to the pull of the
earth. This leads the crawlers toward the tops of branches
where they find suitable food. Their reactions to light, how-
ever, 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 18 or 20 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 molted skin of the second-stage larva
is incorporated with the new scale; a habit characteristic of all
armored scales. In the purple scale most 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. 1B.) The
female begins to lay eggs when about two months old and con-
tinues for three or four weeks, averaging 30 or 40 eggs.
In summer the entire life history extends over a period of
about three months. During cooler weather growth and develop-
ment take place much more slowly, although in our climate
probably seldom wholly cease.
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.
ASSOCIATION WITH WHITEFLIES
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. The real reason is that
12 Florida Cooperative Extension
sooty mold growing in the honeydew secreted by the whiteflies
gives protection to crawlers and young scales. 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 pre-
dators and parasites, both insects and fungi. Extensive tab-
ulations by the writers have shown that the percentage of in-
festations with parasitic 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 usually
is entangled form an ideal refuge for the scales and an old
colony of this whitefly almost invariably shows a heavy infesta-
tion of purple scale. (Fig. 3.)
The seriousness of purple scale damage is shown most clearly
when the scales collect in groups on a leaf, as under a colony
of woolly whitefly. The attacked part of the leaf turns yellow
while other parts remain green. These yellow areas often per-
sist 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, com-
monly called "greasy spots" or "black melanose", have their
origin in attacks of scale-insects. If a large area of the leaf is
attacked by scales the leaf will fall.
Scale attacks on twigs are attended by as serious consequences
as on leaves, a heavy infestation resulting in death of the twig.
On fruit the results of activities by scales are hardly less
marked. If the scales are abundant, the fruit is stunted, ripen-
ing is delayed and coloring is uneven. Vigorous scrubbing is
necessary to remove the scales before packing the fruit. An-
other serious consequence of the presence of scales on fruit is
that punctures made in the rind afford avenues for the entry
of various fungi which cause decay, as previously stated. The
crawlers collect under and around the calyx of the fruit. If
scales are at all abundant on trees, there will always be found
a heavy infestation about and under the fruit calyx, and often
the entire space is covered with a layer of scales several deep.
Citrus Insects and Their Control 13
Fawcett (10) has shown that there is an intimate relation be-
tween the numbers of scales in this situation and the develop-
ment of stem-end rot in the fruit.
The most efficient parasites of purple scale are entomogenous
fungi. Five species are especially common on this scale. In
order of abundance they are the pink scale-fungus, red-headed
scale-fungus, white-headed scale-fungus, black scale-fungus, and
cinnamon fungus. As in the case of those species which para-
sitize whiteflies, these fungi grow most abundantly during the
rainy season. Their development is not, however, so strictly
limited to the summer season as is that of the whitefly-infecting
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 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 dis-
tributed in Florida (and other countries).
To the casual observer it is indistinguish-
able from the red-headed scale-fungus
(Fig. 4). The color of its heads, how-
ever, 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 undoubtedly
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), main-__
ly when on citrus, but also on other hosts; Fig 4. Red headed
obscure scale or water oak scale (Chrysom- scae range). The
phalus obscurus), on water oak; gloomy te no the us
scale or red maple scale (Chrysomphalus Sloared t- (state
entebricosus), on red or swamp maple;
2The scientific names of the fungi as revised by T. Petch (20) and as
given by H. S. Fawcett (12 or per letter to the writer) have been adopted
in the text. The old names are given in footnotes.
SMicrocera fugikuroi Miy. et Sa.
14 Florida Cooperative Extension
California red scale (Chrysomphalus aurantii), on citrus; purple
scale* (Lepidosaphes beckii), on citrus; black thread scale (Isch-
naspis longirostris (Sign.)), on Ficus and other plants; some
RED-HEADED SCALE-FUNGUS (Sphaerostilbe aurantiicola (B.
et Br.) Petch).4-This fungus is very effective against a number
of scale-insects and is widely distributed and common. Its red-
dish heads, smaller than pinheads, grow out from the infected
scales and are easily visible. (Fig. 4.)
The following scale-insects have been found infected by this
fungus in Florida: Purple scale on citrus; San Jose scale (Aspi-
diotus perniciosus), mainly on trifoliate orange, peach, plum
and pear; long scale (Lepidosaphes gloverii), on citrus; ivy
scale (Aspidiotus hederae), mainly on chinaberry; chaff scale
(Parlatoria pergandii), mainly on citrus.
According to records of the Entomology Department, State
Plant Board, and others (5), this fungus also parasitizes Put-
nam's scale (Aspidiotus ancylus), on pecan; latania scale (Aspi-
diotus lataniae), mainly on chinaberry, avocado
and loquat; English walnut scale (Aspidiotus
juglans-regiae), on pecan; Aspidiotus spinosus,
on Bauhinia; 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 pro-
teus, mainly on palms; pine scale (Chionaspis
pinifoliae heterophylae), on pines.
WHITE-HEADED SCALE-FUNGUS (Podonectria
coccicola (E. and E.) Petch).6- (Figs. 5 and
6). It is apparently the first scale-fungus of
which there is any record in Florida and is
figured and described as a "bark fungus" by
H. G. Hubbard (15).
Fg 5. hite- Hubbard, however, failed to discover its
headed scale fungus
on eitrs twig. X" parasitic nature and believed it lived on dead
eura is'e. (sate scales. The writers believe, furthermore, that
Plant Board.) it was this fungus which saved the citrus
industry in the thirties of the last century, when the long scale
had been introduced at Mandarin and St. Augustine, and the
'Splaerostilbe Coccophila Gul.
*This fungus at present appears to be the principal parasite of purple
Citrus Insects and Their Control 15
trees were killed back each year. It is reported that even
whiskey and aloes were tried but were useless in destroying
the scale and reviving the trees. But after
some years the trees recovered, from some
then unknown cause, and it is believed now
that the cause was a friendly fungus, wholly,
or in part at least. Contributing causes may
have been insect enemies of the scales, but as
the insect enemies now present are never so
efficient, the presumption is that it was fungus.
This fungus occurs nearly everywhere in
Florida, wherever there is long scale or pur-
ple scale. As its name indicates, it appears
as small whitish heads growing out from the
It has been found infecting and destroying
the following scales: Long scale, on citrus;
purple scale, on citrus; chaff scale, on citrus.
BLACK SCALE-FUNGUS (Myriangium duriae
Mig. 6. -- White-
Mont.).-This fungus is illustrated in Fig. 7. headed scae-fungus.
Perfect stage. En-
Its distribution apparently is more northerly large twice. (State
than the other fungi, except the red-headed
scale-fungus. Specimens on San Jose scale
have been received from Virginia. This
fungus probably occurs everywhere in Flor-
ida. It has the appearance of black spatter
or black spots.
Insects killed by it are: Purple scale, on
citrus; long scale, on citrus; chaff scale, on
citrus; San Jose scale, mainly on trifoliata,
peach, plum and pear; Putnam's scale,
mainly on pecan; gloomy scale, on maple;
white peach scale (Diaspis pentagona, on
mulberry and peach; English walnut scale,
on Ilex vomitoria and pecan; latania scale,
on holly and chinaberry; mining scale
(Howardia biclavis), on various trees and
Fig. 7.-Black scale- shrubs
fungus. (By H. E. Brat- CINNAMON FUNGUS (Verticillium Cinna-
momeum Petch6).-This fungus occasionally
infects purple scale, long scale, chaff scale, soft brown scale,
6V. heterocladum Penz.
16 Florida Cooperative Extension
as well as whitefly larvae; also palmetto scale, on palmetto;
tea scale (Fiorinia theae), on Camellia japonica; dictyospermum
scale (Chrysomphalus dictyospermi), on Asparagus plumosus;
proteus scale (Parlatoria proteus), on ophiopogon; pyriform
scale (Pulvinaria pyriformis), on citrus and mango; and fern
scale (Hemichionaspis aspidistrae), on fern.
The purple scale is extensively preyed upon by other insects.
These predators are native insects that before the introduction
of the purple scale into Florida fed upon native scale-insects.
They have 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-
8) is by far the
It is very com-
mon i n citrus
groves where it
Fig. 8.-The twice-stabbed lady-beetle. Larva on left, pupa in f e e d s largely
center, and adult on right.
upon the crawl-
ers, and often on the young scales and eggs. It tears up the
females to get them. Like most ladybeetles this one is nearly
round in outline, almost hemispherical in shape. 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 1/5 inch in diameter.
The young, like the larvae of all beetles, is an entirely dif-
ferent 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. 8) 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 larvae often climb
onto a dead twig and attach themselves in a cluster to it.
(Fig. 9.) Ladybeetles do not crawl out of the larval skin when
they pupate but the skin splits length-wise of the back, ex-
Citrus Insects and Their Control 17
posing the pupa within. Life history of the
beetle occupies about a month.
Another ladybeetle (Exochomus marginipen-
nis children Muls.), about /8 inch long, occa-
sionally is found in citrus trees feeding
chiefly on scale-insects, although it has been
seen eating whitefly larvae and aphids. The
wing cases are brown with two comma-
shaped black dots near the tips. The head and
thorax and the abdomen beneath are black.
The larva is black and white. The original
habitat of this species is mostly oak trees where -'
it feeds on native scales and aphids.
The two-spotted ladybeetle (Olla abdominalis
var. sobrina Csy.) (Fig. 46) is very similar
in appearance to the twice-stabbed and has ig. 9.-up a
about the same habits. bbd edy tle
The blood-red (Fig. 44) and the convergent slightly enlared.
ladybeetle (Fig. 45) also feed on scale-insects. However, their
preference is for aphids and they will be described under that
DOWNY DARKLING BEETLE
Epitragodes tomentosus (Lee.)
The downy darkling beetle (Fig. 10), a brown, oval beetle
about 5/16 inch long, is common in citrus trees. Although not
related to ladybeetles, it feeds largely on scale
crawlers. It is very beneficial in controlling
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.
LACEWING FLIES OR APHIS-LIONS
Fig. 10.-Epa- Larvae of lacewing flies are important checks
Sodets t s to scale-insects and aphids. They are flat,
(Lee.). Four times
natural size, (Adapt- spindle-shaped larvae, grayish in color but
ed from Hubbard.)
marked with brown or dull red. The front
of the body ends in two long, slender, sickle-shaped jaws on
which the insect impales its victims while it sucks their body
fluids. This is done through a tube formed by the secondary
jaw maxillaee) fitting over a groove in the true jaws (man-
dibles). These larvae are voracious, attacking insects much
18 Florida Cooperative Extension
larger than themselves. Indeed, they do not hesitate 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 serious. These larvae are particularly fond of aphids,
and therefore are
called aphis lions.
When full grown,
14 to 16 days after
hatching, they seek
some sheltered place
such as a curled
leaf and spin spher-
ical glistening white
cocoons about them-
selves. (Fig. 11.)
Here they remain
for a week or 10
Fig. 11.-Lacewing: Empty cooons. Four times days and then the
emerges. Dr. R. L. Miller has noted (18) five species of aphis-
lions feeding on scale crawlers and aphids.
One may often see an animated rubbish heap moving over
a leaf or the bark of a citrus tree. Close examination 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 dry skins of its victims.
There are two genera of lacewings common in citrus groves.
The adults of one genus are green (Chrysopa), those of the
other brown (Heierobius). 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 parasite emerges. The larvae are
also parasitized by fungi and bacteria which produce fatal
Citrus Insects and Their Control 19
THE GOLDEN-EYED LACEWING
The golden-eyed lacewing (Fig. 12) 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 insect
measures about 11 inches across the ex-
The eggs are laid on top of stiff stalks
/2 inch long and 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 Fng. T12.- den-e sla
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 run-
ning about among them. These are mites. They belong to
the spider class of animals rather than to the insects, as shown
by their eight legs. Insects never have more than six true legs
although 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
Many of these mites feed largely or entirely on the dry
material of dead scales. Others attack living scales although
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 be-
come 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 undoubtedly kill all mites hit by the
spray, but a great many will be found untouched under dead
scales or in other sheltered places.
20 Florida Cooperative Extension
Upon close examination of a group of scales usually it will 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 wasps. They are much
smaller than true wasps and belong to different families. There
are several families of these wasp-like parasites.
In one family, the ichneumon flies, the body usually is 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
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 or in the eggs of a scale-insect either by
inserting her ovipositor under the scale or boring directly
through it. This egg hatches into a soft, whitish, footless, grub,
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.
CONTROL OF PURPLE SCALE
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 to effect 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
Citrus Insects and Their Control 21
females, escaped the first application, time to hatch; but it will
not give them time to mature and in turn lay eggs.
Fig. 13-Increase of purple scale due to spraying the tree with bordeaux mixture:
Top row, sprayed fruit; bottom row, unsprayed fruit.
Lepidosaphes gloverii (Pack.)
Mixed with the purple scales often may be found other scales
almost identical in color and of about the same length, but
straighter and much narrower. These are the long scales. (Fig.
14.) They are closely related to purple scale to which they
bear such a marked resemblance that growers do not ordinarily
distinguish between them.
According to Ashmead (1) this scale was introduced into
Florida about 1835 at Mandarin. By 1860 it had spread over
the orange district and had become so destructive that it threat-
22 Florida Cooperative Extension
ened the existence of the citrus industry. Glover (13), in 1857,
stated that it was entirely free of parasites. This accounts for
its rapid multiplication. Later, parasites, both insects and fungi,
I .- appeared and were finally able to
control it better. Some of these para-
sites probably were introduced from
S '- 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
(15), much more common than the
Purple scale, although now it is much
Its life history, parasites and con-
trol are practically identical with
those of the purple scale. It is a little
more closely confined to the twigs and
branches and less to the leaves and
fruit than the purple scale.
FLORIDA RED OR ROUND SCALE, OR
Chrysomphalus aonidwm (L.)
:" Scale for scale, the Florida red
scale is the most pernicious of Flor-
ida citrus scale-insects. It does less
aggregate damage than 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 citrus belt,
probably because it is almost entirely
confined to leaves and fruit and when
these are removed by a freeze it is
Fi- 14.-Long scale (Lesido-
saph.,- gloverii). Enlarged 4 times, almost exterminated.
(After Merrill and Chaffn.)
Atr Merill nd hn.) This scale is dark reddish-brown
in color, with a conspicuous reddish-brown center, almost cir-
cular in outline (Fig. 15), and about 1/12 inch in diameter
when full-grown. The center is formed by the cast-off first
larval skin. This is nipple-shaped and varies in color from
Citrus Insects and Their Control 23
grayish to a reddish-yellow brassy color. The surrounding part
of the scale, which covers the second larval 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 purple scale.
The mature female under the scale is
bright yellow in color and the shape of
a wide short top.
The scale of the male is only about
one-fourth as wide as 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 ap-
pearance give the impression, at a su-
perficial glance, of a liquid which has
been pressed out from under the scale
and then hardened. This lobe serves
to distinguish a male from a young Fig. .-Florid red cale
female. Chrysomphalus aonidum (L.)
Twice natural lsie.
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 born7 when the females are about 10 weeks old and
continue to be produced 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 commonly parasitize the purple scale only
the pink scale-fungus is found at all common on this scale. At
times it becomes unusually effective.
7Eggs are produced which hatch at once or after a few hours.
24 Florida Cooperative Extension
CONTROL OF FLORIDA RED SCALE
The same oil emulsions which are used against purple scale
are best for this one also. However, because of the thick and
heavy scale which fits the leaf or fruit very closely, 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
not killed by the first spraying time to mature and die and their
last young to emerge, but not allow sufficient time for a new
generation to mature and begin to produce young.
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 should be thoroughly dormant.
Fumigation with hydrocyanic acid gas (see p. 64) has been
particularly effective in combating this scale. The average
kill secured in groves under the senior author's observation has
been between 97 and 98%. Crawlers of this scale do not have
the tendency, so marked in purple scale, to crawl under other
scales and into other protected situations. As a result these
scales are mostly found fully exposed on the surfaces of the
leaves and fruit where they receive the full effect of the gas.
Hence the percentage of kill is higher than with purple scale.
Lime-sulfur with wettable sulfur will kill the crawlers but
not the older stages of this scale.
In spraying fungus into a grove which has considerable Flor-
ida 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.
MINOR ARMORED SCALES
CALIFORNIA RED SCALE
Chrysomphalus aurantii (Mask.)
This scale, one of the worst pests with which the California
grower has to contend, is widely scattered over citrus growing
sections of the world. It is well distributed in Florida but in
Citrus Insects and Their Control 25
most sections has not been serious. In some groves in Pinellas
County it has given trouble.
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 through the semi-transparent scale
that gives this scale the name "red". The pink scale-fungus
sometimes attacks this scale. This may be the reason why it
has never become such a pest in Florida and in the more humid
portions of the West Indies as 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".
RUFOUS OR WEST INDIAN 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 throughout the West Indies.
Pseudaonidia duplex (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
26 Florida Cooperative Extension
this country from Japan. It resembles somewhat in shape the
purple scale but is smaller and darker in color. Thorough spray-
ings with oil emulsions have been used to control this scale, but
the most successful method seems to be fumigation with hydro-
cyanic acid gas.
SAN JOSE SCALE
Aspidiotus perniciosus Comst.
The San Jose scale, a pernicious pest of peaches, plums, pears,
and apples, attacks Poncirus (Citrus) trifoliata. It has been
reported as temporarily attacking young orange trees in groves
where these 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.
Control of this scale on Poncirus trifoliata would be best
accomplished by spraying in summer with the red-headed and
the black scale-fungi and at some time in winter when the
bushes are dormant and leafless with commercial lime-sulfur
solution, 1 part in about 9 of water, as is recommended for
infested peach trees. For a table of dilutions for different
strengths of lime-sulfur see page 88. A 2% oil emulsion applied
during the winter is fully as effective as the lime-sulfur 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 irregularly 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.
Citrus Insects and Their Control 27
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 16 eggs. These are
large for the size of the female, hence the small number. The
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. Crawlers of the first generation are especially abundant
in March or April and of the last in September or October, but
there is much overlapping arid 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 is very efficient 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 through
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 oil emulsions, or fish-oil soap
alone. The best times for spraying are toward the end of the
seasons of maximum abundance of crawlers, which are April
and October. In groves sprayed regularly for whitefly in May
and September the chaff scale will cause no trouble. The only
extra precautions needed 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 leaves and fruit.
Among the most common host plants of this scale besides
citrus are camphor, many palms, Ficus, japonica, mango, and
28 Florida Cooperative Extension
oleander. When growing in an infested grove these plants also
should be sprayed.
CITRUS SNOW SCALE
Chionaspis citri Comst.
The citrus snow scale gets its name from the white color of the
male scales (Fig. 16). These are long and narrow. There is
a prominent longitudinal ridge, and a 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 yellowish in color. Owing to the
M' inconspicuous color of the females it is
the male scales that make a colony notice-
The scale of the female is dark brown
with a lighter margin, a color resembling
the tree bark so closely that the scales
are hard to detect. In shape it resembles
somewhat the purple scale but is broader.
It has a prominent longitudinal ridge
which, with the color and situation on the
tree, readily distinguishes it from the
purple scale. The first larval skin is
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. It is not widely distributed in
Control is the same as for chaff scale.
Fig. 16.-citrus Snow In this group of unarmoredd) soft
scale (Chionasnis citri).
scales, no true scale covering, separate
from the body of the insect, is formed, but 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 fastened permanently to the bark
of the tree, but is able to move about until the eggs begin to
Citrus Insects and Their Control 29
form. At this time the legs are covered and made useless by the
swelling of the body as the eggs form and are more or less
fastened to the branch, leaf, or fruit.
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
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
sooty mold grows and an infested plant soon becomes blackened.
This honeydew is greatly relished by ants which are seen con-
stantly about the scales.
The soft scales seldom seri-
ously injure a mature tree,
but on nursery stock and on
trees recently set the turtle-
back scale sometimes causes
some trouble. After death
these scales soon fall off the
trees instead of remaining
for many months as a crust
which partly shuts off the
light and air as do the ar-
They are easily controlled
by the oil emulsions.
SOFT BROWN OR
Coccus hesperidum (L.)
In this species and the next
described, the wax is incor-
porated with the skin which Fig. 17.-Soft brown scale. Natural size.
becomes tough and parch- (After Comstock.)
ment-like, resembling in appearance the covering of the armored
scales. (Fig. 17.) These scales are larger than the armored
scales and thicker.
30 Florida Cooperative Extension
The full-grown female of this scale is between 1/8 and 1/6
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 mark-
ings on the back of a turtle, hence the name. 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
through 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 nymphs attack only young growth, leaves and
twigs. Consequently this scale increases most rapidly during
flushes of growth in 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
35) has been observed as a very effective fungus parasite of
this scale in several places in south Florida.
The early stages are easily killed by the oil emulsions and int
groves regularly sprayed with them for whiteflies and purple-
scale this scale will be controlled without any special attention.
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-
Saissetia hemisphaerica (Targ.)
The hemispherical scale is similar in size, color, and shape
to the soft brown; but its center is more swollen and the mar-
gin is narrower so that it is nearly hemispherical in profile,
hence the name. It averages about 1/7 inch in length and a
trifle less in width. The height is about 1/12 inch. The egg
,is about 1/150 inch in length and is yellowish-white.
This scale infests guava, avocado, Asparagus plumosus, ja-
ponica, Ficus spp., ferns, peach, rose, palms, and many other
Citrus Insects and Their Control 31
plants, including citrus. Natural and artificial control are the
same as for the soft brown scale.
Saissetia oleae (Bern.)
The black scale (Fig. 18), 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. Florida seems to be the only important citrus center of
the world which does not have consider-
able trouble with this scale.
The adult female 'is from Y8 to 1/4
inch long. It is black or dark brown in
-color and nearly hemispherical in shape.
Markings on the back form a distinct
letter "H". It gives off honeydew in
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 15 to 20 days. The young prefer
the leaves but migrate to the stems be-
-fore they are half grown. They grow
slowly, requiring from six to eight months
to reach maturity (22).
The wax scales are soft scales which
secrete a thick layer of white wax which is.-Back scale. (Ater
completely covers the body. This wax is Wlson. S.)
soft and can be readily scraped off. Underneath the wax the
skin proper is soft and delicate. These scales give off abundant
honeydew. Even a moderate infestation suffices to blacken
thoroughly the host plant.
Three of these wax scales are likely to be found on citrus in
Florida, but only the Florida wax scale is common.
FLORIDA WAX SCALE
Ceroplastes floridensis Comst.
The Florida wax scale (Fig. 19) when not stained by sooty
mold or other foreign matter is snow-white, often with a pink-
32 Florida Cooperative Extension
ish tint imparted to it by the red color of the insect beneath.
Its pure white wax, 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 1/8 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. 19.) 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
The eggs are dark red
Sr and about 1/100 inch long.
S They average in number
between 75 and 100 for
each scale and are placed
under the female which
shrinks as they accumulate.
The pale brown crawlers
show a preference for the
leaves where they collect
especially along the midrib
on the under side. Young
larvae are star-shaped and
even more beautiful than
Fig. 19.-Florida wax scale. (After Wilson, 8e,)
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
maturity. Because of this mortality the insect never becomes
a serious pest of orange or grapefruit trees. On the thick
angular stems of Poncirus trifoliata Raf., it can retain its hold
much better and sometimes becomes more of a pest. The native
Citrus Insects and Their Control 33
food plant of this insect is chiefly the gallberry (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,
feijoa, guavas, cherry laurel, sea grape, Ficus, loquat, mango
and many others. The writers have 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 caterpillar, Laetilia cocci-
divora Comst. (see mealybugs), sometimes' de-
stroys this 'scale. This scale is also very effec- k
tively parasitized by the turbinate fungus.'
Should it become necessary to spray for 'this
scale the oil emulsions will probably be found per-
Ceroplastes eirripediformis Comst.
The barnacle scale is closely related to the Flor-
ida wax, which it resembles in appearance and
life history. Its most conspicuous difference is in
its height which is about equal to its width. (Fig.
20.) The waxy coat is dirty-white in color mot-
tled with brown and is divided into distinct plates.
These plates give the scales a hard, limy appear-
ance, and the angular outline which it shares with
the Florida wax scale, suggests a barnacle in Fig. 20.-Bar-
nacle scale. (Af-
appearance, hence the name. It is larger than ter Wlson, ,4.)
the Florida wax scale, being 1/5 inch long and
1/6 wide. It is a native scale, found throughout 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.
JAPANESE OR MEXICAN WAX SCALE
Ceroplastes ceriferus (Anderson)
The Japanese or Mexican wax scale has been found in a num-
ber of localities in Florida, growing on wild persimmon and
34 Florida Cooperative Extension
gumbo limbo. Citrus, however, is one of its host plants and will
probably be found infested in Florida.
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 through the wax.
i PYRIFORM SCALE
,y. se Pulvinaria pyriformis (Ckll.)
The pyriform scale (Fig.
21) is found on many plants,
by, co c including citru s, guava,
mango, ivy, and many orna-
Smentals. It frequently be-
; comes very abundant on avo-
cados which it blackens thor-
Soughly with the sooty mold
s which grows in its honey-
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
protection to the eggs which
are laid in it. The full-
grown female varies from
1/12 to 1/6 inch in length.
The young are oval, green-
ish-yellow and without any
Fig. 21.-Pyriform scale (Pulvinaria pyri- signs of cotton.
orms) on guava leaf. This scale is easily killed
by contact insecticides, as the oil emulsions, soap solution, kero-
sene emulsion, etc.
The Cuban Aschersonia (Aschersonia cubensis) and Cephalo-
sporium lecanii have been observed frequently as very effective
fungus parasites of this scale. The Cryptolaemus ladybeetle
also feeds on this scale.
Citrus Insects and Their Control 35
GREEN SHIELD SCALE
Pulvinaria psidii Mask.
In Florida the green shield scale has attacked chiefly the wild
rubber tree, guava, mango, sea grape, and avocado in about
the order named. Only occasionally has it been taken from
citrus in Florida, and is said to be the worst pest citrus has
in southeastern Asia.
Fig. 22.-Green shield scale (Pulvinaria psidii Mask.) on leaf of wild fig, or wild rubber
(Ficus aurea). After Wilson, 34. Enlarged twice.
The adult female forms cotton even more abundantly than
its related species, the pyriform scale. The mass finally be-
comes many times larger than the scale proper, which is about
the size of the pyriform scale but more oval in outline, and
lighter in color. (Fig. 22.) It is greenish-brown. This scale
is now widely distributed in south Florida.
ENTOMOGENOUS FUNGI OF SOFT SCALES
A number of fungi do very effective work in parasitizing soft
scales. The following are the most important ones:
CUBAN ASCHERSONIA (Aschersonia cubensis Berk. and Curt.).8
sAccording to Petch (courtesy H. S. Fawcett, letter 1924) this has
perfect stage in Hypocrella epiphylla.
36 Florida Cooperative Extension
-This fungus (Fig. 23) consists of buff, brown or reddish
pustules 1/16 to nearly 1/4 inch in diameter. Frequently it
has been collected effectively destroying the liriodendron scale
on banana shrub at Gainesville. It appears to be widely distrib-
uted, however, and has been received from widely separated
localities in Florida and from Porto Rico and Cuba.
The chief importance of this fungus lies in the fact that it
has been received infecting and destroying several important
pests of the soft scale group. Pure cultures of this fungus were
first grown by the junior author in 1920, and are occasionally
available for distribution.
This fungus has been received on the following scales: Soft
brown scale (Coccus hesperidum), on citrus; liriodendron scale
Fig. 23.--Cuban Aschersonia on pyriform scale on guava leaf. Plant Board photo by
A. H. Beyer, courtesy of Experiment Station. Slightly reduced.
(Toumeyella liriodendri), on banana shrub and magnolia;
tessellated scale (Eucalymnatus tessellatus), on mango, cape
jasmine and dahoon holly; pyriform scale (Pulvinaria pyri-
formis), on guava, avocado, rhynchospermum, bottlebrush, red
bay and other plants-this scale rarely occurs on citrus in Flor-
ida; green scale (Coccus viridis), on unknown plant from Cuba;
Florida wax scale (Ceroplastes floridensis), on fern; Lecanium
nigrofasciatum, on red bay.
TURBINATE FUNGUS (Aschersonia turbinata Berk.) .-This
is the parasite that controls Florida wax scale. It produces one
or several short whitish stems that grow out from the mass of
fungus covering the scale. These stems approximate 1/16 inch
in height and diameter and end in a shallow cavity containing
9According to Fawcett (1926) this has a perfect stage in Hypoorella
turbinata (Berk.) Petch.
Citrus Insects and Their Control 37
the red or near-red spores. It probably occurs wherever Florida
wax scale is abundant on citrus and other plants. It has also
been received on the liriodendron scale, on banana shrub.
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,
cover the entire insect. It has been received from the West
Indies, and various localities in Florida. The importance of
this fungus lies mainly in its being an effective parasite of the
pyriform scale, which, while but a minor pest of citrus in Flor-
ida, 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 green scale
(Coccus viridis (Green)) on citrus in Ceylon (19) 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 mango
in the Virgin Islands; Coccus acuminatus (Sign.) on mango in
Barbados; liriodendron scale on magnolia and banana shrub;
tessellated scale (Eucalymnatus tessellatus (Sign.)) on palms
and some other plants; Toumeyella turgida on pine (Pinus
taeda) (Fawcett, 9).
This fungus can be readily grown artificially in pure cultures,
should a need for doing so arise.
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 throughout life and are
able to 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 controlled by those natural
checks. They give off large amounts of honeydew in which a
particularly heavy growth of sooty mold develops, blackening
the whole colony and all surrounding vegetation.
38 Florida Cooperative Extension
COMMON, OR CITRUS, MEALYBUGS
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 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 crevices of the bark.
Fig. 24.-Citrus mealybug; infestation on grapefruit.
Mealybugs often collect around the stem end of the fruit.
Frequently they get under the calyces where they are respon-
sible for the falling of much young fruit, particularly grape-
fruit. In this situation they are entirely hidden and only after
the fruit has dropped can one detect the presence of mealybugs
on the old calyx. A specially favored place is the sheltered nook
formed by two or more fruits in contact. This is more fre-
quently the case with grapefruit than with other citrus) conse-
Citrus Insects and Their Control 39
quently mealybugs are rather more troublesome to grapefruit.
Grapefruits become blackened with a particularly copious and
sticky honeydew which, with the sooty-
mold (Fig. 24) makes a vigorous scrub-
bing necessary before they can be
packed. Also, they are apt to cause an
uneven color of the ripening fruit, the
coloring process being delayed in the
The female grows to a length of from
1/10 to 1/4 inch. Her color varies from
white to light brown, with brown legs Fig. 25.-A mealybug. (From
and antennae. (Fig. 25.) The male is
small, light colored, and has two long white threads of wax
The female lays from 350 to 400 eggs in the mass of cotton
which she secretes. The eggs hatch in from eight to 10 days in
summer, but twice this time is required in winter. The larvae
require from six to 10 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 usually
)control them fairly well. Among such predators are ladybeetles
and their larvae, the larvae of lacewing flies, trash bugs, and
syrphus-flies, and the scale-eating caterpillar, Laetilia coccidi-
vora. The latter is a dark red caterpillar 2 inch in length. It
makes covered passage-ways of silk among the scales on which
it feeds. The adult is a grayish-brown moth 1/3 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 insects that otherwise would feed upon them.
During 1930 the Experiment Station imported from Cali-
fornia a species of ladybeetle, Cryptolaemus montrouzieri,
which came originally from Australia. This ladybeetle, often
called "Crypt", feeds especially on mealybugs. The Experiment
Station raised thousands of these beetles on mealybugs which
in turn were raised on the sprouts of potatoes and other plants.
These beetles were distributed widely over the State of Florida.
40 Florida Cooperative Extension
They have been found in the spring showing that they can live
throughout the winter out-of-doors, at least during a mild winter,
such as the ones of 1931-2 and 1936-7. However, usually very
few ever survive the winter and to obtain any appreciable
amount of control of mealybugs by their use it will be necessary
to reintroduce them each spring as is done in California where
they are- extensively used. These beetles are being raised on a
commercial scale by one insectary in Florida and sold to growers.
MEALYBUG FUNGUS (Entomophthora fumosa Speare).-This
fungus was- discovered in Florida in 1920 on the citrus mealy-
bug by Dr. A. T. Speare (25), at that time in, the employ of the
Bureau of Plant Industry. It may become very effective during
the period of summer rains, but may allow the mealybugs to
increase inordinately during spring. However, it appears to be
always present on infestations of mealybugs whenever proper
weather conditions occur.
Mealybugs killed by this fungus appear "to be enveloped in
a dark slate-gray woolly covering", whence the specific name
fumosa (smoky). At other times some dead ones "appear jet
black, almost glistening" without the woolly covering.
In Florida this fungus has been found infecting the citrus
mealybug (Pseudococcus citri). From Louisiana Dr. Speare
received it on the citrus mealybug, and also on a species of
Phenacoccus mealybug infesting hibiscus.
Methods for growing this fungus in artificial cultures in the
laboratory have not been discovered.
CONTROL OF MEALYBUGS
Careful spraying will reduce mealybug numbers. It is import-
ant to have good pressure to force liquid into corners and crev-
ices, and also to wash many of the insects from their support.
Washing them off the trees is so effective that spraying with
clear water often is sufficient to control them, yet it is better
to use an insecticide. One may use one of the oil emulsions
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 emulsion 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
Citrus Insects and Their Control 41
thoroughly. However, unless one has a good agitator he should
not try this, as burning may result from indifferent mixing.
Another good spray mixture is one pint of nicotine sulfate and
a gallon of an oxidized oil derivative in 100 gallons of water.
The most effective spray we have ever tried is a commercial
Mealybugs are more abundant on some ornamentals than on
citrus. These, when grown about a citrus grove, may be a source
of infestation on citrus 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 on 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 mealy-
bug are the same as those of the common mealybug.
Icerya, purchase Mask.
This notorious pest of citrus, native of Australia, was intro-
duced into Florida from California in 1893. It was carried to Cali-
fornia in 1868 and a dozen years later had reached the citrus
sections where it threatened 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 ladybeetle
was found preying on the scale and was introduced into Cali-
fornia in 1889. It increased rapidly and soon had the scale under
While this mealybug has never been as serious a menace here
as in California it caused much trouble until, through the efforts
42 Florida Cooperative Extension
of the Experiment Station, the Australian ladybeetle was
brought here also. The experience in California was repeated
here. The Vedalia seldom exterminates the scale from a grove
but always keeps it under at least fair control. Sometimes the
scale will increase for a time and become
quite conspicuous, but then the Vedalia
also increases and soon checks the scale.
For 15 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. It is now generally dis-
tributed throughout the State.
The cottony-cushion scale (Fig. 26) is
brown and has somewhat the appearance
of a soft scale. When the egg-laying period
arrives, the female forms a large mass of
cotton which elevates the posterior portion
of her body until she stands almost on her
head. This soft, cottony cushion, in which
500 to 800 eggs are laid, may reach a length
of nearly a half inch, and is ridged length-
wise. Because of these longitudinal ridges
this scale is also called "the fluted scale".
Adults are found usually on the bark of
trunk, limbs, or twigs; but the young fre-
quent the leaves, especially 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
crevices and forks of twigs.
Ausiig. 2a.-daye t Besides citrus, the insects are partial to
edalia, feeding on the roses. The careless shipping of cuttings
about the State is probably responsible for
the rapid spread of the insect. In the Annual Report of the
Florida Agricultural Experiment Station for 1915 (29), is a
longer list of host plants. In the Quarterly Bulletin, State
Plant Board of Florida, Vol. III, No. 4, is a complete host list
Citrus Insects and Their Control 43
Time required for development varies from three to four
months or more, even in summer. There are about three gen-
erations a year but no distinct broods. This scale increases
most rapidly during dry seasons but is more apt to persist
during the rainy season than is the mealybug. Ants carry these
insects from tree to tree, and should be controlled in a grove
infested with cottony-cushion scale.
CONTROL OF COTTONY-CUSHION SCALE
Though much more expensive and troublesome than by the use
of Vedalia, cottony-cushion scale can be kept under control by
spraying. Efficient solutions are lime-sulfur and oil emulsions
used to control other scale-insects and whiteflies. The same
thiocyanate recommended for mealybugs is effective. On a few
dooryard trees frequent washing with a strong soap solution
may be sufficient, especially if the adult females with their
eggs are rubbed off.
VEDALIA OR AUSTRALIAN LADYBEETLE
The only permanent and satisfactory method of controlling
this scale in a large grove is by the introduction of the Vedalia
or Australian ladybeetle (Rodolia (Novius) cardinalis (Muls.))
(Fig. 27.) This is much smaller than most native ladybeetles,
being only 1/8 inch long. It is of a cardinal-red color, spotted
and fringed with black. The larva (Fig. 26)
which also feeds 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 cottony sac of the
female scales, but' sometimes on the nearby
branches. Each female lays up to 50 eggs per Fig. 27.-Austra-
day. The eggs hatch in five or six days and li" ardili.) Eo-
the young larvae at once begin to feed on the large drawing.
eggs of the scale. As they grow larger they feed also on the
scales, both old and young. The larvae require about three
weeks for growth and another week is spent in the pupal stage.
These pupae are scattered singly about among the scales and
are found most frequently on the leaves. (Fig. 28.)
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 ladybeetles to clean
44 Florida Cooperative Extension
up an infestation so quickly. This is usually accomplished in
three or four months after the introduction of the beetles.
Except for an oc-
casional citrus aphid,
Vedalia feeds only on
cottony cushion scale
or turns cannibalistic,
if the scale becomes
scarce. Therefore, when
the supply of scales in
a grove runs low, the
Vedalia may die out.
After the disappearance
of the beetles, the scale
may again multiply in
the grove. It may then
be necessary to reintro-
duce the Vedalia, al-
though experience in
Florida has shown this
to be seldom necessary.
As soon as the scale
again becomes abund-
ant, the beetles almost
Fig. 28.-Pupae of the Vedalia, or Australian laydbeetle. probably flying from
Twice natural size.
adjoining groves. Some
observations of the writers show that the Vedalia has found
colonies of the cottony-cushion scale at least two miles from
where the beetles hatched (29).
Colonies of Vedalia are being supplied to growers for $1 each
by the State Plant Board, Gainesville.
The native, twice-stabbed ladybeetle (Fig. 9) does good work
against this as well as other scales, but it cannot be depended
upon to control the scale as well as the Vedalia. Trash bugs
and the scale-eating caterpillar also have been seen to feed upon
COTTONY-CUSHION SCALE FUNGUS (Spicaria javanica Bally).10
-This fungus covers the infected scales with a delicate, gray-
ish-lavender, powdery growth. It probably is the same fungus
10ldentified by Erdman West.
Citrus Insects and Their Control 45
that Gossard observed destroying cottony-cushion scale in Pinellas
County in 1899 (14). Occasionally specimens of it are received
on this scale. According to Gossard, this fungus may become
very effective when weather conditions (abundant warmth and
moisture) are suitable. However, alone it appears not to have
been capable of effectively keeping the cottony-cushion scale in
check without the assistance of the Vedalia.
Where or how this fungus holds over between outbreaks of
the scale in Florida is not known. In Ceylon it occurs on a wax
scale (Ceroplastes), on green scale (Coccus viridis), cottony-
cushion scale (Icerya purchase), the caterpillar of Euproctis
flava and on egg masses of another insect (Homona cafearis).
Bally described it on a beetle, Stephanoderes hampei, in Java.
It can be easily grown in pure cultures, on plugs of sweet
potato, should the need for doing so arise. For the present,
however, the Vedalia effects an almost perfect control of the
cottony-cushion scale, so that this need has not appeared.
WHITEFLIES OR ALEYRODIDS
Eight species of whiteflies have been found on citrus in
Florida. In the order of their abundance they are:
1. The common, or citrus, 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, Paraleyrodes perseae (Quaint.)
6. Inconspicuous, or sweet-potato, whitefly,
Bemisia inconspicua (Quaint.)
7. Mulberry whitefly, Tetraleurodes mori (Quaint.)
8. Florida, or guava, whitefly, Trialeurodes floridensis
Whiteflies are sucking insects. Indeed, they are quite closely
related to scale-insects, and like them the young nymphall)
stages are 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 as in scale-insects, both sexes are
winged and active. The presence of winged females enables
the insect to spread much more rapidly from tree to tree and
from grove to grove and greatly increases the difficulty of
46 Florida Cooperative Extension
The life history of all whiteflies is very similar and one dis-
cussion will answer for all, although the time spent in develop-
ment will vary with different species. As with all insects, there
are four stages in the development of the whitefly-egg, larva
(or nymph), pupa, and adult (or imago).
The whitefly egg is nearly oval in outline, and very small.
It is usually less than 1/100 inch long and about half as wide,
barely visible to the
unaided eye. When
abundant the eg gs
give the citrus leaves
an appearance of be-
ing covered with a
mealy dust. (Fig. 29.)
The eggs are laid on
the under side of the
leaves of the host
Fig. 29.-Common (citrus) whitefly: Adults and eggs, plants to which they
on leaf. (After Gossard.)
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
nymphs crawl about for a few hours, but have a distinct aver-
sion 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 nymphs (Figs. 31 and 36) never
move again, but remain anchored; 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 nymph seems scarcely to resemble an in-
sect, as commonly known. This process is re- Fig. S2.-The cal-
peated twice. fornia whitefly-eating
p. ladybeetle (Delphasts
The fourth stage nymph (Figs. 32 and 37) drain). Enlarged
differs; considerably from these in other stages.
It takes much less food, is thicker, and the organs of the adult
whitefly begin to: form. This stage corresponds to the ,pupal
stage of most insects. After a more or less prolonged pupal
Citrus Insects and Their Control 47
stage (the time depends much upon the temperature) the pupal
case splits across the back and the adult insect emerges. In this
stage the insect differs greatly from the
nymph. It has the typical three parts of the
usual insect body-head, thorax, and ab-
domen-and is provided 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 entomologi-
cal 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, although the Fs. .1-Common (it-
male is a bit smaller than the female. Sp) whiefy: Firstg ge
nymph. (After Berger, 4.)
COMMON, OR CITRUS, WHITEFLY
Dialeurodes citri (Ash.)
In most sections of the State this is the most common whitefly
and the one the grower has in mind when he speaks of "whitefly".
Fifteen or 20 years ago it was our most destructive citrus insect
and still holds that distinction in the satsuma belt. During the
past few years, however, it has undergone a striking reduction
in numbers in the peninsular part of the State. It still, how-
ever, does an immense amount of damage. It injures citrus
trees in three ways:
1. It withdraws immense quantities of sap. This is a serious
drain on the trees, checking their growth and that of the fruit.
Fruits on badly infested trees are always fewer and inferior
2. Nymphs of whiteflies throw off from their alimentary tract
large quantities of honeydew. This falls on leaves and fruit
and in it grows the fungus 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.
48 Florida Cooperative Extension
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 light from the leaves and thus interferes
S 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 been treated
under purple scale.
The eggs (Fig. 33) of this
species are pale yellow and
are scattered singly over the
leaves, a marked preference
being shown for young
leaves. Each female lays
about 100 eggs in the course
Fig. 2.--Common, or citrus, whitefly: Fourth- f her life of a week or 10
stage nymph. (After Berger, 4.)
days. Most of them hatch
in from 10 to 12 days. The summer brood spends about three
weeks in the nymphal 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
10 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 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, especially if the weather is exceptionally warm.
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. 34.)
FOOD PLANTS OF COMMON, OR CITRUS, WHITEFLY
The common whitefly has been observed to mature on the
following plants, arranged approximately in order of prefer-
Citrus Insects and Their Control 49
Preferred Less Severely Infested
Chinaberry and umbrella tree Laurel cherry
Citrus, all varieties and species Coffee
Satsumas Smilax sp.
Round oranges Wild olive (Osmanthus americanus)
Trifoliata Green ash
Kumquats Japonica (Camellia japonica)
Lemons Jessamine (Jasminum sp.)
Limes English ivy
Grapefruit Native persimmon
Cape jasmine (Gardenia) Water oak
Privet Trumpet flower (Tecoma radicans)
Prickly ash Picus sp.
Japanese persimmons Scrub palmetto
Button bush (Cephalanthus occiden-
Mexican orange (Choisya ternata)
Osage orange (Maclura aurantiaca)
Portugal cherry (Cerasus sp.)
The wild and useless plants in the above list; particularly
those near the head, should be destroyed when growing near
groves. Of these the
chinaberry and um-
brella trees are particu-
larly important. T he
planting of these trees
in citrus communities
should be prohibited by
public sentiment and by
law. It has been esti-
mated that a good-sized
chinaberry t r e e will
produce on the average
between 25,000,000 and
each season. From
these trees the adults of
the late summer brood
Fig. 33.-Eggs of common (citrus) whitefly. Magni-
fly out to infest citrus fied. (After Berger, 4.)
trees when the matur-
ing leaves of the chinaberry are no longer attractive.
50 Florida Cooperative Extension
PARASITES AND PREDATORS
In Florida but few insects, and virtually no higher animals,.
feed upon the citrus whitefly. This is undoubtedly because it
is an imported insect which has left its enemies behind. In
India, probably its native home, several insects prey upon or
parasitize it, and an unsuccessful attempt was once made to
introduce some of them (35).
II I I II i Ii I II I iI I II
I I I I I I .. I I .1
II 1 I I ': I I I I
I. I JI
( I I II I 1 I I I I I V 1
I I\ I- I I I.I I "I_ I Z I 1 1:,1
II` i L-* 'i i_- i.- ll, i i i i - ji I
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
Woolly whitefly. --- Common citrus whitefly. ..... Cloudy-winged whitefly.
Fig. 34.-Diagram showing relative date of emergence of adult whiteflies.
(From Bul. 126, 29.)
The twice-stabbed ladybeetle (described under purple scale)
(Fig. 8) destroys some crawlers and occasionally an older larva,
but prefers other food, especially scale crawlers. A tiny, dark
brown ladybeetle, Delphastus pusillus (Lec.), seems to be very
fond of the eggs, but for several reasons never becomes suffi-
ciently abundant to be of much practical benefit. A related
species, Delphastus catalinae (Fig. 30), an efficient enemy of
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 con-
sidered as a single species. The junior author, then entomologist
to the Experiment Station, first separated the two species (4).
He named this insect Aleyrodes nubifera. The most marked
differences are in the egg, which is black in this species (Fig.
35), and in the fact that this species is attacked by another
Citrus Insects and Their Control 51
species of fungus, the yellow aschersonia, in addition to those
that attack the common whitefly.
Black eggs or the yellow fungus on the leaves will at once
acquaint the grower with the presence of the cloudy-winged
the past few years
this species h a s
much more abund-
ant and in many
sections in the
southern part of
the State is now
the dominant spe-
cies, and in some
sections D. citri
is absent. The
cies is less com-
mon in the north-
ern part of the
citrus belt. Before Fig. 35.--Eggs of cloudy-winged whitefy. Magnified.
the "big freeze" of
1894-95 this species was common over the entire citrus belt,
but as its food" in Florida is confined mostly to citrus it was
exterminated in much of the northern part
Sof the citrus belt by the entire loss of the
leaves from the trees in that region.
DESCRIPTION OF CLOUDY-WINGED
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.
35.) The females of this species show
an even greater fondness for new growth,
particularly watersprouts, than do those
Fig. 36.-Cloudy-winged of citri. The leaves of watersprouts are
hitefly: First-stage ymph. often so thickly strewn with eggs as to
be distinctly blackened.
The nymphs (Figs. 36 and 37) closely resemble those of citri
ilOther hosts are Ficus nitida, one or two other species of rubber, and
yam vine, all very sensitive to frost.
52 Florida Cooperative Extension
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 its shape as does that of citri.
The adult, too, is similar but in the 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
an imperfect winter
brood is less common
than with citri and the
summer broods lag be-
hind those of that spe-
cies, as shown in the
diagram (Fig. 34).
The maximum flight
of the spring brood of
adults occurs in early
Fig. 87.-Cloudy-winged whitefly: Fourth-stage nymph. April, a b o u t three
(After Berger, 4.)
weeks later than that
of citri; the summer brood 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
(citrus) 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 grower should spray at the time
recommended for the common species. Although 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
Citrus Insects and Their Control 53
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 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
In spraying the fungi where this species is present, the yel-
low Aschersonia may be added to the others.
Aleurothrixus 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, a foremost authority on this
group of insects, states that it is identical with the whitefly
which was collected from the sea grape (Coccolobus) 25 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 (29). It would seem most prob-
able then that, although it is a native insect which has long
lived on the sea grape, it has comparatively recently developed
a strain which has taken 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 de-
veloped elsewhere and was introduced into '
Florida 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, but .
it was quickly subdued by a little wasp-like /
parasite (Eretmocerus haldemani). (Fig. 38.)
The dense mat of wool (Fig. 39) which per- .S.-E
sists for months on the leaves makes an excel- GreatY ty merged.
(From Bul. I26.)
lent place in which young purple scales can
hide, and much woolly whitefly in a grove has always been
54 Florida Cooperative Extension
followed by a heavy infestation of purple scale. This is per-
haps the most serious phase of an infestation of woolly whitefly.
The name woolly whitefly is derived from curled waxy fila-
ments which completely cover the pupa and have the appearance
of wool. The empty pupal cases of this species are very per-
sistent and remain on the leaves for many months after the
adults have emerged.
Fig. 39.-Leaf infested with woolly whitefly. (From Bul. 126.)
The eggs are brown in color, and curved in shape somewhat
like a short sausage. They are laid mostly in circles (Fig. 39).
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 lays eggs on nearly mature
leaves, often on the leaf on which she herself was raised.
The first-stage nymphs 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 nymphs 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
Citrus Insects and Their Control 55
short distances. On the other hand, they will cling tenaciously
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.
Although 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 chief parasite is Eretmocerus haldemani. This insect lays
its eggs in the larvae of the whitefly. The grub of the parasite
feeds on the substance of the whitefly nymph and finally kills
it. The parasite pupates inside its host, which markedly swells,
and emerges about the time the adult whitefly should emerge.
These parasites are so abundant that they have invariably con-
trolled infestations of this whitefly, 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 recommended for
use against other species. It is imperative, however, that the
oil be applied before many larvae have reached the third stage,
as the dense mat of wool more or less smeared over with honey-
dew protects third- and fourth-stage larvae from the oil. Most
favorable periods for spraying are late February or early March,
early June, the middle of August, and about November 1.
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.
FLORIDA, OR GUAVA, WHITEFLY
Trialeurodes floridensis (Quaint.)
The Florida 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.
56 Florida Cooperative Extension
Paraleyrodes perseae (Quaintance)
The bay whitefly resembles somewhat the woolly whitefly in
the larval stages and one might easily confuse them. But this
species lacks the curly wool, although it has the straight waxy
plates. These plates break up, when the adult emerges from the
pupal case, into short rods scattered about the sluggish winged
insect which squats in the center, presenting an appearance sug-
gestive 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 red bay (Ta-
mala). It is common but seldom abundant in citrus groves.
Only once has the senior author seen a grove that needed spray-
ing 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.
INCONSPICUOUS, OR SWEET POTATO, WHITEFLY
Bemisia 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 citrus trees. It is markedly smaller in both
larval and adult stages than the other whiteflies. Otherwise,
it resembles citri quite closely. It is parasitized by red Ascher-
sonia. It has never been sufficiently abundant to demand con-
trol measures. Should it do so, doubtless it can be controlled
by oil emulsions.
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. Although present
on a variety of trees, including mulberry and persimmon, it
has never given any trouble to citrus growers in Florida. How-
ever, the same insect, or a variety or strain of it, is said to be
a serious pest of oranges in Mexico.
Aleurocanthus woglumi Ashby
This is another dangerous aleyrodid, apparently first intro-
duced in America into Jamaica and found there in 1913. It now
Citrus Insects and Their Control 57
occurs in Cuba, the Bahamas, Panama, Costa Rica, and presum-
ably other tropical American countries.
More than 60 species of host plants are listed for the New
World: citrus, coffee, mango, avocado, guava, sapodilla and
banana are preferred.
More recently it has been introduced into the island of Key
West, presumably through the smuggling of plant material from
Cuba. A vigorous eradication campaign by the State Plant
Board of Florida (Bureau of Entomology and Plant Quarantine,
U. S. D. A., cooperating) has been waged for several years, and
appears to be on the verge of success.
Like. the two species (Dialeurodes citri and D. citrifolii) most
troublesome to citrus in Florida, its native home is southeastern
Asia, in this instance Malaya and the East Indies. There a
number of parasites and predators hold it in check. To reduce
the threat of this pest to Florida, several of these were intro-
duced into Cuba (1929-1931) through the joint efforts of Cuba,
the Bureau of Entomology, U. S. D. A., and the State Plant
Board of Florida.
Of the several parasites introduced into Cuba, one, Eretmo-
cerus serious Silv., has been a marked success, reducing the black-
fly from a very severe pest which threatened the very existence
of the citrus industry there to a minor one. From the laboratory
established near Havana parasites have been introduced into
other West Indian islands and Central America.
Two ladybeetles, Cryptognatha sp. and Scymnus smithianus
Silv., also were successfully introduced into Cuba. Indications
are that the former may be very effective at certain seasons;
the effectiveness of the latter is doubtful.
The descriptive word "black" applies to both the larvae and
the adults. As the body of the adult is dark brown and the
wings are smoky with a white cross, the general impression to
the unaided eye is bluish-black.
It has been shown that the use of certain highly refined oils
in emulsion, when properly and intelligently applied as a spray,
give rather effective control of the blackfly.
RED ASCHERSONIA (Aschersonia aleyrodis Webber).-Also
known as red whitefly-fungus. This fungus (Fig. 40) 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,
58 Florida Cooperative Extension
Panasofkee, and other places in Florida. It forms pink and red
pustules 1/8 inch or less in diameter. The fungus is pink but
the spore masses are red and give it the red color. It is an im-
portant factor in the control of common whitefly (Dialeurodes
citri) and cloudy-winged whitefly (Dialeurodes citrifolii) on
citrus. The junior author has also observed it abundantly in-
fecting a whitefly on sweet potato, probably Bemisia inconspicua,
Trialeurodes ruborum on blackberry, Aleurodicus cardini on
guava, and specimens of an unknown black aleyrodid heavily
infected by this fungus have been received from Fort Myers,
Florida. Other unidentified aleyrodidae on dahoon holly and
swamp bay in hammocks, and Tetraleurodes mori on French
mulberry, at times also become infected with it. According to
records kept by the Entomological Department of the State Plant
Board, this fungus is a useful parasite of the blackfly (Aleuro-
canthus woglumi) in Cuba, Jamaica, and Costa Rica.
This was the first fungus grown in pure cultures by the Plant
Board, based on methods developed by Dr. H. S. Fawcett while
at the Florida Experiment Station (1906-1911).
Fig. 40.-Red whitefly-fungus, or red aschersonia, showing roundish white areas
with black centers, the pink and red fungus pustules. Natural size. (Bul. 67.)
YELLOW ASCHERSONIA (Aschersonia goldiana Sacc. et Ellis).12
-The yellow whitefly-fungus was discovered at Winter Park,
Florida, by P. H. Rolfs in 1906. It resembles red aschersonia
(Fig. 40) in general appearance. The fungus growth, itself,
is cream-color or nearly white, but when this becomes covered
with masses of ripe yellowish spores the color becomes a kind
12A. flavo-citrina P. Henn.
Citrus Insects and Their Control 59
of yellow. It is effective only against the cloudy-winged white-
fly but is probably no more effective against this species than
the red aschersonia. Pure cultures are sometimes available.
Fig. 41.-Brown whitefly-fungus. Natural size. Round black areas are the
BROWN WHITEFLY-FUNGUS (Aegerita webberi Fawcett).-
Figure 41 is an excellent illustration of this fungus, which was
discovered in 1896 by Dr. H. J. Webber at Manatee, Florida.
It forms brown pustules about 1/8 inch in diameter on the under-
side of the leaves of citrus infested by either the common citrus
or the cloudy-winged whitefly. As this fungus, 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 effective. It also thrives later in the sea-
son after dry weather has set in. This fact is probably due to
its habit of growth just explained. The fine fungal threads re-
ferred to also finally grow around the edge of the leaf and even-
tually 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 or parts of leaves
assume a cinnamon-brown color. While most of the spores are
formed on top of the leaf, some also are formed underneath.
Unfortunately, methods for growing this fungus in pure cul-
tures have never been successful.
State Plant Board records also show this fungus as a useful
parasite of the blackfly (Aleurocanthus woglumi) in Cuba.
60 Florida Cooperative Extension
WHITE-FRINGED FUNGUS (Fusarium aleyrodis Fetch).13-This
fungus was first noticed by P. H. Rolfs in 1907 at Sutherland,
Florida. It has since been found widely distributed through-
out the State. This fungus 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 larvae
die without evidence of another cause, it is the white-fringe
fungus that is present. It is found on both the common 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 has not been
undertaken, although it is easily grown in pure cultures.
CINNAMON FUNGUS (Verticillium cinnamomeum Petch14).-
This occurs occasionally on citrus, infecting whitefly larvae,
chaff scale, soft brown scale, purple scale and long scale. It
also infects these and other similar insects on other plants
(page 15). In appearance its pustules are like the brown fungus
but with a powdery surface and cinnamon color. It is widely
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.
CONTROL OF WHITEFLIES AND SCALE-INSECTS
As stated under the heading of purple scale, the control of
whiteflies and scale-insects is a single problem; control measures
are the same.
The common method of controlling whiteflies and purple scale
in Florida is to spray the trees with an oil emulsion.
Time to Spray.-As explained previously, 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-
13Microcera sp. Fawcett.
14V. heterocladumr Penz.
Citrus Insects and Their Control 61
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 broods 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 stated before, whitefly eggs hatch
in about a week. The younger the larvae the more easily they
are killed. Therefore it is important to spray as soon as prac-
tically all eggs have hatched. Another reason for spraying early
is to avoid the drain on the trees resulting from the feeding
of the larvae. Although most of the fall brood of whiteflies
are usually on the wing during the last of August and the first
week in September, there are a good many slowly developing
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 the date. About 10 days later when practically
all eggs have hatched will be the most favorable time to spray
for whiteflies. This will bring the date to the last part of Sep-
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.
Water standing on the leaves will dilute the spray solution and
make it ineffective. Trees should not be sprayed with this oil
emulsion when the temperature is 900 or above, particularly
if the sun is shining brightly. Under these conditions one is
liable to get serious burning of the fruit. Sometime then in
late September or early October, conditions are usually right
for spraying with oil emulsions for whiteflies and scale-insects
and the spraying should be done promptly. 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
One exception, however, must be made to early fall spraying.
In the case of early varieties such as satsumas, Parson Brown
62 Florida Cooperative Extension
oranges, etc., the fall spraying should be delayed until after
the fruit has been picked. As first pointed out by W. W. Others
(36), spraying with oil emulsions delays the ripening of the
fruit. With early varieties the price usually is so much better
early in the season that the grower cannot afford to delay the
ripening of his fruit except in the case of a very heavy infesta-
tion. Neither should varieties like Hamlins, with a particularly
tender rind, be sprayed at this time as they are easily burned.
With the spring brood of the common whitefly, on the wing
usually in late March, again the grower should wait until the
brood has disappeared and give 10 additional days to allow the
eggs to hatch. This would bring the spraying in April, but
it is not quite safe to spray with an oil emulsion 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 spraying sometime in May or June.
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
spraying. However, a good clean-up spray, particularly in the
early fall, is much to be recommended, as trees thoroughly
sprayed at this time should remain reasonably free of insect
pests throughout the winter.
Under special conditions it may be desirable to apply the oil
emulsions at other times. Trees sprayed with bordeaux to con-
trol scab or melanose should usually be sprayed in June with an
oil emulsion to counteract the increase of scale-insects due to
the killing of the entomogenous fungi by bordeaux, and to the
residue which it leaves. This is very important. If a grove
becomes heavily infested with scale-insects during the winter
it should, of course, be sprayed before the spring flush of growth
makes spraying unsafe.
Spraying Solutions.-The spray solutions most used in the
past for controlling scale-insects and whiteflies are emulsions
of various oils. Two general types of these are on the market.
One is made from the so-called "red" oils. Recently more highly
refined oils have been used. These can be used on more tender
foliage than the older oil emulsions, as they are distinctly less
liable to burn. Usually, however, they are more expensive.
Citrus Insects and Their Control 63
The old oil emulsions generally used soap as the emulsifying
agent. One, called the "cold mix", does not need heat. It has
the following ingredients.
Fish-oil soap ........................................ 8 lbs. or 1 gallon
Lubricating oil, 24 or 28 Baume ................... ........ 2 gallons
W ater ... .................. ............................. ........... 1 gallon
If the water used for spraying is hard it should be softened.
The following directions for preparing it are copied from
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 many oil emulsions on the market. They differ
not only in character of oil used and the emulsifying agent, but
also in amount of oil contained, hence in the concentrations to
be used. In all cases follow the directions on the container. In
most cases the diluted spray should contain at least 1 percent
of actual oil.
It has long been known that lime-sulfur sprays would kill
the crawlers of scale-insects and usually the first anchored stage.
Experiments by W. L. Thompson of the Citrus Experiment Sta-
tion (27) have shown that on the whole two sprayings of lime-
sulfur in the spring are about equivalent to one spray of oil
emulsion in the control of scale-insects and whiteflies, and at
the same time give much better control of rust mites. This
combination of rust mite and scale-insect spray has been much
used in the last few years. The addition of from 5 to 10 pounds
per 100 gallons of wettable sulfur to the lime-sulfur enables
one to cut down the amount of lime-sulfur used and hence makes
the spray safer to use on tender foliage and during hot weather.
Wettable sulfur not only adds sulfur to the solution, making it
more effective in controlling both rust mites and scale-insect
crawlers, but also is an excellent spreader. This work is thor-
oughly discussed in Bulletin 282 (27).
One precaution must be observed. A spray of oil emulsion
and one of lime-sulfur must not be applied too close together.
At least two weeks should intervene, more if there has been
but little rain. A mixture of lime-sulfur and an oil emulsion
on leaves and fruit is liable to result in burning.
64 Florida Cooperative Extension
Fumigation has been tried repeatedly in Florida but has never
made much headway with growers, due to several objections.
The early methods could be used only at night and during a
comparatively few weeks of winter. In these early experiments
the hydrocyanic acid gas was generated first by the old pot
method in which sodium cyanide is dropped into a pot contain-
ing dilute sulfuric acid under a tent; later by a cyanafumer in
whiic the gas is generated in the same manner but in a separate
machine (cyanafumer) outside of the tent. The use of liquid
hydrocyanic acid also has been tried in Florida.
More recently a method of fumigating citrus trees has been
used which overcomes some of the above objections. 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. The cost is of course greater
as compared with a single spraying. Sometimes, however, the
reduced number of fumigations necessary may, under at least
some conditions, compensate for the greater cost of the individ-
ual operation, especially for the Florida red scale. Where white-
flies 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 fumiga-
tion would have to be repeated.
Fumigation should be tried only by experienced men. Inex-
perienced growers should hire it done by such men rather than
attempt to do it themselves. Furthermore, the cost of tents
renders the method prohibitive if the small grower has to pro-
vide his own tents. The dust ordinarily used in fumigating
trees is mixed with 15% of sulfur to kill more effectively rust
mites as well as scale-insects and whiteflies.
CONTROL BY FUNGUS PARASITES
There are at least six fungus parasites known to infect white-
flies infesting citrus, and about as many more on scale-insects
(3). On whiteflies these are: Red Aschersonia, yellow Ascher-
sonia, brown whitefly-fungus, cinnamon fungus, white-fringed
fungus, and occasionally a species of Sporotrichum. All these
fungi, except 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-
Citrus Insects and Their Control 65
insects are: The red-headed scale-fungus, pink scale-fungus,
white-headed scale-fungus, black scale-fungus, Cuban Ascher-
sonia, turbinate Aschersonia, Cephalosporium fungus, and cin-
Fungus 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 red Aschersonia are so small
(and they vary in size) that from 13,000,000 to 52,000,000 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 through 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, pro-
duces 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.
Florida is indeed fortunate in having so many of these para-
sites to assist in the control of its insect pests. Abundant rain-
fall and high temperatures during the period of summer rains,
from about June through September, provide conditions under
which fungi thrive. The importance of fungi in keeping down
scale-insects, for instance, can be easily demonstrated by spray-
ing a tree with a fungicide, such as bordeaux mixture. This
destroys the fungi and the scales increase, a fact discovered
independently by many citrus growers. Whenever it becomes
necessary to spray with bordeaux, and scale-insects or white-
flies are present, this should, as a rule, be followed after some
weeks with an insecticide, as otherwise the scale-insects or white-
flies may so increase as to seriously injure the trees.
Fungi are not recommended as a panacea, but principally as
an aid in the control of scale-insects and whiteflies. The fungi
do not thrive in all kinds of localities nor under all conditions
in which groves may be found. As previously indicated, they
66 Florida Cooperative Extension
thrive best during the period of summer rains. Sometimes, how-
ever, favorable weather conditions prevail earlier, as early as
April, and the brown fungus thrives later in fall than the others.
The junior author also once observed an unusual development
of the red-headed scale-fungus during a warm February (Gaines-
ville, 1909). But while these exceptional instances occur, ex-
perience and observation all indicate that 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 trans-
planting. Unusually favorable weather conditions may, of
course, result in a fungus controlling either the scale-insects
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
either scale-insects or whiteflies before introducing fungus or
spraying with oil, but should at all times know exactly the insect
condition of his trees, and use the treatment indicated for the
time and place. During the period of summer rains we recom-
mend 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.
HOW TO INTRODUCE FUNGUS
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 (seeds) 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. 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 pure
cultures when available are to be preferred as they are perfectly
Citrus Insects and Their Control 67
free from all other fungus spores and diseases, which may not
be true of fungus taken from trees. Cultures of red Aschersonia,
yellow Aschersonia and Cuban Aschersonia are obtainable from
the Plant Board. 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
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
fungi if allowed to stand in contact too long.
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 the
loose leaf in its natural position
so that insects may crawl over
it and scatter the fungus spores.
Scale-fungus material may be
applied also by cutting small
pieces of twigs and tying these
onto the limbs and twigs of the
scale-infested trees. (Fig. 42.)
PURE CULTURES OF FUNGUS
Since 1915 the State Plant
Board of Florida has been grow-
ing and supplying pure cultures
of red Aschersonia, or red
whitefly-fungus, at cost of pro- I
duction. A few cultures of yel-
low Aschersonia, Cuban Ascher-
sonia and the Cephalosporium
SFig. 42.-A scale-fungus applied by ty-
fungus also are sometimes avail- ing a piece of twig with fungus onto a
scale-infested twig. (After Rolfs and Faw-
able. A culture consists of the cett, s28.)
68 Florida Cooperative Extension
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 furnishing these fungi at one dollar
per culture, with directions for using them. The red Ascher-
sonia will infect both the common 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 20 or 30 leaves collected at random from
their worst infested trees for examination in order to determine
whether only one of these fungi is required or whether the re-
quest may be filled with both kinds.
Address: "Entomological Department, State Plant Board,
: Four species of aphids or plant lice are commonly met with
pn.citrus in Florida. They are, in order of importance:
1. The green citrus aphid (Aphis spiraecola Patch).
2. The melon aphid (Aphis gossypii Glover).
3. The brown citrus aphid or grapefruit aphid (Toxoptera
( ra ntia.e (Fonsc.)).
4. The green peach aphid or the common garden aphid
(Myzus persicae Sulz.). The last three are minor pests. But
,during the springs of 1924, 1925, 1932, and 1937, the green
Citrus aphid was a pest of considerable importance.
SThese aphids ordinarily can' be distinguished by their color.
The green 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
green 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 green citrus aphid but is much smaller.
Often a colony of aphids will consist of two or three of these
Citrus Insects and Their Control 69
THE GREEN CITRUS APHID
Aphis spiraecola Patch
This aphid first attracted attention as a citrus pest during
the spring of 1923, although 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 are many
records of earlier infestations of aphids, but usually the species
involved was the melon aphid.
The origin of the citrus aphid is a mystery. Its native hosts
are undoubtedly shrubs of the genus Spirea, of which the bridal
wreath is the species most commonly grown in Florida. The
insect is undoubtedly closely related to the apple aphis of the
north (Aphis pomi) and Miss Patch, who described Aphis spi-
raecola, now regards it as identical with that species. As a
citrus 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
Fig. 43.-Foliage curled by the green citrus aphid. (After Beyer, 8.)
70 Florida Cooperative Extension
spread during the springs of 1924 and 1925 to the entire citrus
belt of the peninsula. In the summer of 1925 Mr. Others found
it in one citrus section of California (40), where apparently it
had been established for many years, and it has been found in
Besides spirea and citrus, it attacks the Japanese flowering
quince, haw apple, pear, laurel cherry, and a considerable num-
ber of herbs. Most of these are rather accidental hosts and
will be found infested only in heavily infested groves. The sow
thistle (Sonchus), fireweed (Erechthites), and Mexican tea
(Chenopodium ambrosioides) apparently are 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
winter comes on, usually about the last of November, true males
and females are produced. These differ markedly in color from
the parthenogenetic aphids in that they are a bright straw yel-
low. These females lay eggs which in more northern sections
carry the species throughout 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
especially wild crabapple in the northern part of the State.
The rate of breeding and growth depends very much upon the
temperature. During early May it takes about six days to com-
plete their development, or six days after birth an aphid usually
begins to bring forth young. The average rate at that season
is five per day. As the weather gets warmer not only the rate
of growth but the number of young produced per day diminishes.
In June it takes eight days to produce a generation and the
average number of young produced is only two per day. This
slowing up of breeding during summer undoubtedly has much
to do with 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 101/2 days.
ENEMIES OF CITRUS APHIDS
In common with other aphids, the green citrus aphid is sub-
ject to attacks by a large number of enemies which during most
Citrus Insects and Their Control 71
of the year keep down their numbers. Occasionally in spring
when weather conditions are favorable for the aphids, the ene-
mies are unable to hold it in check.
Among the most important enemies of the green 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 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 stages
varies with the species of ladybeetles, but the above represents
Cycloneda sanguine immaculata (Fab.)
This (Fig. 44) is the most important ladybeetle feeding on
the green citrus aphid. It is common throughout the entire
year. An adult
of this species
will eat, on an
aphids per day,
the larvae aver-
age about 16 per
day. Larvae of
these beetles are
tacked by a fun-
Fig. 44.-Blood-red ladybeetle. Adult, left; pupa, center;
gus d i s e a s e larva, right.
and to a lesser extent by two hymenopterous parasites, Tetras-
tichus blephyri and Homolatylus terminalis.
Hippodamia convergens Guer.
This (Fig. 45) is the second most important ladybeetle
which feeds on the green citrus aphid. In late spring it ap-
proaches in abundance the blood-red ladybeetle, but during the
winter and early spring it is not numerous. It is predominately
a southern species which needs warm weather for its develop-
72 Florida Cooperative Extension
ment. This ladybeetle 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 com-
4. V. infested with
the turnip louse
0 and cabbage
Spouse and on
Fig. 45.-Convergent ladybeetle. Larva, left; pupa, center; crops.
The egg stage
lasts from-three to four days, the larva from 13 to 16, and
the pupa from four to seven days in April and May. There
is also a prebviposition 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.
The chief check on the multiplication of this ladybeetle is a
disease which appears.to be caused by a bacterial organism.
It is very common and destructive.
A larva of this species eats from 40 to 70 aphids per day,
while an adult eats nearly 90.
Ola abdominalis var. sobrina Csy.
Up to the middle of April this (Fig. 46) is the second most
abundant ladybeetle in colonies of the citrus aphid. After that
dat e, though
it actually in-
creases in num-
bers, it is
forced into sec-
ond place by .
the rapid rise
in numbers of
the convergent Fig. 46.-Two-spotted ladybeetle. Larva, left; pupa, center;
ladybeetle. I t
appears to reach its maximum about May 1 and in June becomes
very scarce. In April it takes about four days for the eggs to
Citrus Insects and Their Control 73
hatch. The larval stages occupy 23 days, the pupal six days, and
the preoviposition period about 11 days, making the time from
one generation to another about 44 days. A larva of this species
eats, on the average, about 20 aphids per day. The larvae are
very subject to a fungus disease caused by a species of Clado-
SCYMNUS TERMINATUS Say.
This little ladybeetle (Fig. 47) seems to be preeminently a
summer species and by the end of June is the most common
aphids. The lar-
vae of this ge-
nus are of strik-
because of a
dense covering '
of white hairs. *
trash bugs at
first g 1 a n c e. Fig. 47.--SCmnue terminat.. Larva, left; Dupa,. center;
Larvae of this
species are heavily parasitized by a wasp-like parasite, Anisos-
Other ladybeetles found feeding on this aphid were Scymnus
brullei Muls; Scymnus collaris Melsh. (Fig. 48); Scymnus cre-
m u s margini-
Muls. (Fig. 49),
a little red lady-
black spots on
the wing cov-
Fig. 48.-Scymnus collaris ladybeetle. Larva, left; pupa, ers; Microwei-
center; adult, right.
(Ashm.), a very small ladybeetle with the front part of the
wing covers red, the back part and the thorax black; Stethorus
utilis (Horn), the smallest of all the ladybeetles, scarcely
larger than the head of a pin, smooth and shining black in
74 Florida Cooperative Extension
color; Ceratomegilla fuscilabris floridana (Leng.), a spotted
ladybeetle occasionally found infesting colonies of the citrus
aphid in low
s beetle is also
o aon the citrus
aphid, but prob-
ably never com-
pletes its devel-
Fig. 49.-Ezochomus marginipenis children. Larva, left; the
pupa, center; adult, right opment there.
Leis dimitata var. 15-spilota Hope
In June 1925 the Experiment Station imported from Cali-
fornia a ladybeetle very much larger than any native species.
As this ladybeetle came originally from China it is referred
to as the Chinese
50). A larva of
this species eats
an average of
nearly 200 young M
aphids per day,
and an adult an
The Leis lady-
beetle has become b
lished in Orange
County where it
has usually given
trol of aphids, a
very little dam-
Only in years of Fig. 50.-Chinese ladybeetle. a, eggs; b, larva; c, pupa; d, adult.
aphid infestation, like the spring of 1937, has it failed to do so.
The beetle was sent out to over 100 localities in the State
and has become established inf only one other to date. It is
not an easy matter to establish this ladybeetle in a grove (33).
Citrus Insects and Their Control 75
Life History.-The eggs of this species hatch during warm
weather in three days, during winter in five days. Larvae re-
quire 11 days to mature. They remain in the pupal stage five
days. Thus during warm weather their life cycle occupies 23
days and during winter 35 days. There is also a preoviposition
period of 30 days. A female lays on the average about 71 eggs.
Next to the ladybeetles, syrphus fly larvae are the most im-
portant insect predators on aphids. In almost any colony estab-
lished as long as a week, one or more of these legless yellow
maggots may be seen crawling about and impaling aphids on
its sharp beak. These insects are more abundant in the early
spring. Some species seem to disappear entirely in May. Like
the larvae of the ladybeetles, they are heavily parasitized by
both vegetable parasites (fungi and bacteria) and insects. Three
wasp-like parasites were bred out from the syrphus flies dur-
ing our studies of the citrus aphid in 1925.
The adults of these larvae are two-winged flies.. (Fig. 51.)
These flies feed on the nectar and pollen of flowers and often
may be seen
They have the
ability to hover
in front of a
flower like a
ing on it. The
eggs are rather
large f or the Fig. 51.-Syrphus fly, Paccha lugens. Left to right, adult,
size of the flies
and glistening white in color. They are laid among the aphids
where they are conspicuous objects.
Syrphus wiedmanni 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, and re-
appeared in October. One larva of this species ate 513 aphids
in 10 days. Two others ate an average of 41 and 44 aphids
76 Florida Cooperative Extension
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, November
to January, and is found during every month of the year.
Baccha clavata Fab.: (Fig. 52.) This syrphus fly larva be-
late in the sea-
son, reaching its
late May or
1Z early June and
continues to be
found in colon-
-ies of aphids all
Fig. 52.-Syrphus fly, Baccha clavata. Left to right, adult, larvae o f this
much subject to a disease, apparently of bacterial 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 17.
Several fungus diseases at times are very destructive to
aphids. The most common of these is caused by the fungus
Empusa fresenii Now. Warm, humid weather for 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 and
again in 1937 this disease thoroughly 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 mul-
W. A. Kuntz, of the Plant Pathology Department, Florida
Experiment Station, who has given this fungus a close and
exhaustive study, thus describes the appearance of infested
aphids (16) :
Citrus Insects and Their Control 77
"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 throughout.)
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
CONTROL OF APHIDS
Heavy, dashing rains are very destructive to citrus aphids,
which are washed off the plants and pounded to death on the
ground. After heavy rains it often happens that the only live
aphids to be found are 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.-Since 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"
It should be the grower's aim to accentuate this natural
tendency of a citrus tree to grow in flushes. Most important
dormant period is that of the winter season. The most important
factor in throwing a tree into dormancy in the winter is un-
doubtedly cold and next most important drouth. However, there
are practices under the grower's control which have a tendency
to make trees grow in winter. Heavy applications of nitrogen
late in the fall may do this and should be avoided on young
trees. 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
of young trees should be applied not later than October. Sickly
78 Florida Cooperative Extension
trees apt to be putting out growth at unseasonable times should
Winter Treatment.-During winter the grower should make
an especial effort to get his grove free of aphids. Generally
only young trees need attention at this time. Water sprouts
and other sporadic shoots 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
Dipping.-On young trees much of the winter growth is
apt to be on ends of branches. A very thorough and cheap
method of dealing with this tender growth is to dip the infested
ends of branches. A good insecticide for this purpose is a
solution of nicotine sulfate, one pound to 800 pounds of water,
and about an
ounce or two of
soap for each gal-
lon of water. A
compound of der-
ris will also make
an excellent dip
as it will not burn
should be placed
in a bucket into
w h i c h infested
twigs can be bent
over and dipped.
T h e liquid will
enter the curled
leaves and should
give 100% kill.
or Spraying. -
Early in spring
Fig. 53.-A home-made mixer for mixing nicotine sulfate with w hen young
hydrated lime. (After Beyer, 6.)
sprouts are apt to
start in the interior of the tree where they cannot be dipped,
spot dusting or spraying (see page 81) should be resorted to.
If dusting is to be employed it is necessary that the atmosphere
Citrus Insects and Their Control 79
be perfectly quiet. Enough wind to tell from .what direction
it is coming is sufficient to interfere with dusting. The temper-
ature also should be above 60 degrees. A satisfactory dust is
a 3% nicotine sulfate-lime dust. This can be purchased already
mixed or made at home at a considerable saving in cost by mix-
ing in a barrel (Fig. 53) 3% pounds of 40% nicotine sulfate
and 50 pounds of hydrated lime.
A cheaper dust can be made from free nicotine. This is sold
as a solution of 50% nicotine. A 2% dust of this free nicotine
(i.e. 2 pounds of the 50% nicotine solution in 50 pounds of
lime) has given as good a kill as a 3% dust of nicotine sulfate.
If growers will free their groves of aphids during winter they
will not be much troubled with aphids flying in from other
groves during early spring.
During most seasons there is very little migration of aphids
from grove to grove until about the middle of March. By this
time growth has usually commenced to harden on some trees
causing the aphids to produce wings and fly away. Usually,
up to the middle of March, most of the aphids in any particular
grove have been raised there during the winter.
Fig. 54.-Young trees tented ready for dusting.
Dusting.-The most thorough and usually the cheapest way
of dealing with aphids on bearing trees during the spring flush
of growth is to dust the grove with a nicotine sulfate-lime dust
through a power dusting machine. It is absolutely essential that
the atmosphere be quiet. The cloud of dust should hover about a
tree for a full minute. If there is too much breeze to allow this,
dusting should not be attempted as it would be inefficient.
80 Florida Cooperative Extension
The dust to be used in these power dusters is the same as
that recommended for spot dusting. Some power dusters are
so constructed that the lime and nicotine compound can be
mixed in the hopper. This type of dusting machine eliminates
the great waste of nicotine which takes place while the dust is
being transferred from the mixer to the dusting machine. Ex-
perience has shown that a 2% dust of nicotine sulfate or a 11/2 %
dust, made from 50% free nicotine will give good control when
mixed in these self-mixing dusters.
Dusting Under Tents.-Young trees, up to a height of seven
or eight feet, can be most thoroughly freed of aphids by dusting
them under a tent (Figs. 54 and 55). By using tents the oper-
ator is independent of the wind. If the weather is warm, 70
,or:ab1ove under the -tents, exposure of a minute will be suffi-
cient. Qno of these tents, will cost. from $1.00 to $3.00 accord-
ing to size. and by using a half dozen or more one has a battery
which will enable him to work continuously, i.e., by the time
he has dusted trees under the last tent he can move the tent
from the first tree dusted to, a fresh tree. To make these tents
more nearly .ust-proof they can be painted or dipped into melted
Citrus Insects and Their Control 81
paraffin. The following formula also will make them dust-tight
and has the further advantage of preventing mildew:
40 gal, water 1 lb. zinc sulfate
1 lb. sal soda 2 oz. tartaric acid
Dissolve the three chemicals separately in small quantities of
water, then place in larger body. Allow cloth to remain in this
solution 24 hours. Will last from 7 to 10 years.
Spraying.-Any good contact insecticide will kill all aphids
hit; lime-sulfur, 1 to 50, is fairly effective. As the common
oil emulsions are apt to burn tender foliage one must be care-
ful in their application. However, it is usually safe to use a
gallon of these oil emulsions in 100 gallons of water. This
makes an excellent spreader to combine with nicotine sulfate.
Soap is the spreader commonly used for nicotine, five or six
pounds to 100 gallons of water. However, the oil emulsions
make a better spreader for growth which is sturdy enough to
stand them. Emulsions made from white oils are safer than
those from red oils. Most excellent spreaders also are some of
the pine tar soaps. Certain oil derivatives (penetrol) also are
excellent spreaders and will enable one to reduce the amount
of nicotine to about one-fourth of what is required when soap
is used as a spreader, i.e., one part of 40% nicotine sulfate will
suffice for 3,000 parts of water. This materially cheapens the
cost of the insecticide.
Wettable sulfur also may be added to lime-sulfur and nicotine
spray as a spreader and to increase its efficacy as a control of
It is not as easy to get a spray into the curled leaves as it
is to get a dust.
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 Young Trees Early.-Young trees set late in winter or
spring may be so severely attacked by aphids that they will
be killed outright. If possible young trees should be set during
early winter. Experience has shown that the first flush of
growth on small trees set in December is not attacked by aphids.
However, sprouts from large trees transplanted at that season
are liable to be attacked. Apparently the sprouts which a small
tree puts out when transplanted are not sufficiently succulent
to attract aphids.
82 Florida Cooperative Extension
It is important to bring the spring flush of growth through
without too much damage from aphids. Trees will then go
dormant in late spring and the aphids will largely be starved out
before the June flush of growth starts. If aphids prevent a
tree from putting out its full spring flush of growth, the tree
instead of going dormant may continue its efforts to put out
new growth between flushes and furnish the aphid with con-
stant food supply. Ordinarily it is only the spring growth that
will need attention. Due to the slowing up of breeding of aphids
during summer, heavy
rains and attacks of fun-
gus diseases, the summer
flush of growth ordinari-
ly is not much troubled
THE MELON APHID
Aphis gossypii Glover
During most seasons,
next to the green citrus
aphid, the melon aphid
is the most common one
on citrus. However, it
rarely becomes suffici-
ently abundant to make
control measures neces-
sary as it is commonly
held in check by natural
enemies. In addition to
the natural enemies men-
tioned for the green cit-
Fig. 56.-Parasitized bodies of the melon aphid. rus aphid, the melon
aphid is heavily parasit-
ized by a minute wasp-like insect. This parasite lays an egg
in the aphid. From this egg hatches a grub which feeds on
the tissues of the aphid, finally killing it. Parasitized aphids
swell until they become almost spherical in shape (Fig. 56).
Dead aphids turn a brassy brown color. The grub of the para-
sit9 after reaching full size inside the aphid turns into a pupa
and finally the adult wasp emerges through a round hole chewed
in the top of the aphid. These greatly-swollen aphids with round
holes in their abdomens are very common sights in a colony of
Citrus Insects and Their Control 83
melon aphids. Although this parasite occasionally attacks the
green citrus aphid, the vast majority of the grubs fail to emerge.
The parasitized citrus aphid swells like the melon aphid, but
turns a deep reddish brown color. The grub of the wasp nearly
always dies without emerging. Failure of this parasite to work
in the green citrus aphid is the reason for the heavy infestation
of this aphid.
Eriophyes oleivorus (Ash.)
Next to scale-insects the rust mite is the most expensive guest
the citrus grower entertains. It is a sucking animal which ex-
tracts the oils from both leaves and stems, although 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 thinner than
that of a bright fruit from the same tree. This alone results in
reducing the size of the fruits and hence more are required to
fill a box. The fruit fails to develop properly, especially if in-
jured early in the season, resulting in a further reduction in
size, and as oranges are commonly sold by the box, the grower
loses money on small fruit. Also a small fruit that otherwise
would be marketable may become a cull when its size is further
reduced by the mites. Although 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 lower prices. 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
84 Florida Cooperative Extension
Although they do not show it so plainly, the leaves are really
injured 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 skin
called "buckskin". This in its origin is perhaps not due entirely
to the rust mite. Other factors, possibly a fungus, may con-
tribute to its development. However, if the rust mite is con-
trolled in a grove, "buckskinning" disappears.
The rust mite (Fig. 57) 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
V0 of the fruit and leaves.
S The mite is light yellow and wedge-
shaped. It is broadest in front and
tapers uniformly to the posterior end
a where there are two small lobes, false
feet which the mite 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
Sd full-grown it is 1/200 inch long. The
young are a little paler in color than
Fig. 57.-Rust mite: a, dorsal the adults and broader in proportion to
view; b, lateral view-enlarged,
the dot in circle indicating nat- their length.
ural size; c, leg; d, egg, with
embryo just about ready to
hatch-more enlarged. (After LIFE HISTORY
The eggs are large for the size of the
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 10 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 begins
so that an entire generation may develop in a fortnight. This
rapid development enables the mites to multiply enormously in
a short time if weather conditions are favorable (42).
The mites move about considerably. As they exhaust the oil
from one cell they move to the next. On a smooth surface,
Citrus Insects and Their Control 85
such as an orange leaf, they can cover 10 or 12 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 awayon it with the wind may carry many rust mites with
them. Rust mites avoid both direct sunlight and dense 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 remain
bright on the other. Sometimes a ring of rust is formed around
the fruit where the intensity of the light is most satisfactory 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 predaceous thrips (Aleuro-
dothrips fasciapennis) being among the most important. How-
ever, they cannot be depended upon to control the mites.
As shown by Yothers (41), sudden severe cold is very fatal
to mites, adults, young and eggs being destroyed.
CONTROL OF RUST MITES
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 10 or 15 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 hanging to the
tree, such as the "June bloom" of the previous year, is most
86 Florida Cooperative Extension
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 "bright". Fruit once russeted will
never be bright again although the rust may become a little less
noticeable as the fruit colors. The grower who has permitted
his fruit to become russeted can, and of course should, prevent
further damage by promptly spraying, if the mites are still
The only way to be sure of having bright fruit is to watch
it constantly and as soon as 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 pre-
cautionary measure. Although this practice is undoubtedly
preferable 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 in-
crease in the number of mites.
SULFUR THE BEST PREVENTIVE
Like all members of the spider class, rust mites are very
sensitive to sulfur. Sulfur 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; the sulfur 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 sulfur, or some of its compounds,
applying it dry, or in the form of a spray. Free sulfur is one
of the best remedies against red spiders, or mites. It remains
active for a long time, frequently two or three weeks, and
usually kills the mites.
Sulfur 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, and the presence of other pests which may be con-
trolled at the same time.
Citrus Insects and Their Control 87
Dusting is much more rapid than spraying. A grove can be
dusted in from one-fourth to one-tenth the time it 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 usually will give better control.
Growers with large groves will find dusting more economical
than spraying. But small growers may well hesitate about
going to the extra expense of buying a dusting machine.
Growers must have access to a sprayer to control scale-insects
and whiteflies and, if the grove is not too large, it will be eco-
nomical to use the same spray outfit for controlling rust mites.
The greatest advantage of dusting over spraying is the
rapidity with which it can be accomplished. Rust mites multiply
very rapidly if 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 though 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 12 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-
For dusting one may use simply finely ground sulfur. The
more finely ground the more readily it goes through the dust-
ing machine. Commercial makers of sulfur dusts frequently
add from 10 to 15% of hydrated lime to the product. This
makes it go through some of the dusting machines more readily
than the pure sulfur.
Sulfur works better when the nights are moist and the days
bright and sunny; under these conditions decomposition takes
place more rapidly.
Many growers make the mistake of applying too little sul-
fur to their trees and consequently get poor control. A large
bearing tree will require, according to size, from a quarter to
a half pound of sulfur dust. If there is much wind blowing,
even more will be required to give good coverage.
88 Florida Cooperative Extension
Lime-sulfur is the spray solution commonly used for rust
mites. Use about 1 gallon to from 40 to 65 gallons of water.
The grower can make his own lime-sulfur by boiling lime and
sulfur together over a fire, but this does not ordinarily pro-
duce as good a compound as the commercial product. The pro-
duct, especially the home made, is apt to vary considerably in
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-sulfur at any degree of concentration likely to be en-
countered. For convenient reference there has also been in-
cluded the amount to use as a winter wash to kill San Jose
scale on either P. trifoliata or peaches or plums and also the
amount to use as a fungicide on citrus during summer.
TABLE 1.-DILUTION TABLE FOR LIME-SULFUR SOLUTION.
Baume Number of gallons of water to one gallon of lime-sulfur
reading For a winter wash ( As a fungicide For rust mite
36 91/2 34 77
35 9 331/ 74
34 8% 32 71
33 81/4 31 68
32 8 30 65
31 7%V2 29 62
30 714 28 59/
29 7 27 57
28 6 26 54
27 6% 241/2 51
26 6 23/2 48
25 5% 22% 45
24 51/ 21 42
23 5 19 391/2
22 4% 181/ 361/
21 4% 17 34
20 4 17 31%
19 3% 161/2 29%
18 | 3% 15/4 27%
17 31/% 141/2 25%
16 3 13 23%
15 2% 12% 22
Aside from its value as a control for rust mites, lime-sulfur
seems to act as a stimulant to the fruit, increasing its size, caus-
ing it to ripen earlier, and improving the texture of the rind.
Citrus Insects and Their Control 89
During the past two years the plan of adding from five to 10
pounds of wettable sulfur to each 100 gallons of lime-sulfur
spray has come into general use. The addition of wettable sul-
fur not only increases the amount of sulfur in the spray and
hence the kill of rust mites but is a most efficient wetting and
The use of lime-sulfur as a combination spray for rust mites,
scale-insects and whitefly has already been discussed.
Wettable sulfur may also be added to bordeaux, which is
applied to control scab and melanose on citrus fruits. From
five to 10 pounds of wettable sulfur in 50 gallons of bordeaux
gives the longest control of rust mites of anything we have
ever tried (27). The bordeaux acts as a sticker to retain the
wettable sulfur on the foliage. Blood albumen is another most
excellent spreader for lime-sulfur. Wettable sulfur may also
be added to sprays of zinc.
Two species of spider mites infest citrus in Florida. One, the
six-spotted mite, is pale grayish-yellow with six dark spots
arranged 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, although they prefer other food,
especially aphids. Aleurodothrips also feeds upon them.
Control in each case is the same as for rust mites, but they
are not killed as readily by sulfur dust during cool weather.
Tetranychus sexmaculatus Riley
The six-spotted mite attacks the under side of the leaves
where it spins thin, tent-like webs under which it lives. As
a result of its sucking the leaves turn yellow in the spots under
the web. These spots increase in size as more sap is with-
drawn until finally the whole leaf becomes yellow, curls, and
falls. If many leaves are lost the fruit also falls from the
devitalized trees and the financial loss occasioned thereby is
90 Florida Cooperative Extension
direct and severe. The young show few or none of the six
spots which are characteristic of the adults.
Paratetranychus 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
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 Poncirus 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 14 threads of silk which run out in as many directions,
like guy ropes of a derrick, and are fastened to the surface of
The eggs hatch in a week or two and the young require about
12 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 30 to 75 eggs.
FLORIDA FLOWER THRIPS
Frankliniella cephalica bispinosus Morgan
The Florida flower thrips (Fig. 58) is a minute, soft-bodied
insect about 1/25 inch long and is very common in many flow-
ers, including citrus blossoms. Its color varies from yellow to
orange. The abdomen is commonly lighter colored 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, although on the tenderer parts of the skin it is 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, thin and membraneous and fringed with
relatively long hairs. The young are very similar to adults
but lack wings, and are lighter in color.
Citrus Insects and Their Control 91
CHARACTER AND EXTENT OF DAMAGE
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 scar-
ring it and making it unattractive in appearance.
Fig. 58.-Florida flower thrips: Adult female. Highly magnified. (Drawing by Dozier.)
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 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 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
receptacle also that most of the eggs are laid and here the larvae
of the next generation can be found feeding after both stamens
and petals have fallen and most of the adult insects have flown
to more inviting fields. If sufficiently injured, this receptacle
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-
age the insects do to the setting of the fruit may, if the bloom
92 Florida Cooperative Extension
is heavy, be small. The results of several years of experimenta-
tion with this insect indicate that on trees which have a heavy
bloom and a moderate number of thrips, or even a heavy infesta-
tion 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 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.
THRIPS MARKS ON THE FRUIT
Feeding by thrips on the ovaries or young fruit causes smooth,
br6wnish, sunken areas in the shape of streaks and blotches,
and often circles about the fruit. These sunken areas resemble
scars made by the wind rubbing a leaf or a stem against the
young fruit, but these latter scars are usually rough and raised
Fig. 59.-Thripa and wind injury marks on grapefruit.
Citrus Insects and Their Control 93
above the general surface, whereas those made by thrips are
sunken and smooth. Figure 59 shows both types of scars.
These sunken areas have a thinner skin than the remainder of
the fruit and are more liable to attacks of fungi and insects,
such as the pumpkin bug, than is healthy skin. This damage
usually is done when the fruit is less than three weeks old. It
is mostly the work of young thrips that hatch 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 fallen.
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 4 percent was counted
as culls. This is the greatest amount of damage noted. Usually
it will not exceed 5 to 10 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
average. The nymphal stage is of 10 to 24 days' duration, aver-
aging 15 days. The last two days are spent as pupae. Although
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.
The entire life history thus requires about 23 days 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
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. Most important
of the predators is a small bug, Triphleps insidious Say, very
94 Florida Cooperative Extension
common among the thrips and flowers. Some other species of
thrips are predaceous and feed upon flower thrips. The flower
thrips does not seem to be attacked 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 1 percent surviving. The rain knocks them from the flowers
and pounds them to death on the ground.
As previously stated, present information would indicate-
that thrips usually are 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 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 3 to 8 percent..
On a few trees with scanty bloom and abundant thrips it has
increased the amount 300 percent. On the average the propor-
tion of scarred fruit was reduced about 50 percent by one-
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 10 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. Nicotine is
very effective and a little soap, lime-sulfur, or oil derivative to
act as a spreader is necessary.
The following, first used against another thrips in the orange
groves of California, has given good results in Florida:
Commercial lime-sulfur solution, 32 degrees Baume .... .......... 2% quarts
Nicotine sulfate ................................................ ................ ... .... pint
W ater ....... ........................................... .. ... .. ........ ..... ..... 50 gallons.
Some growers spray lime-sulfur into the bloom of grape-
fruit and satsumas to control scab, using it at a strength of 1
Citrus Insects and Their Control 95
part to about 40 parts of water. In that case it is necessary
only to add the 31/2 ounces of nicotine sulfate to the lime-
sulfur solution. By the use of certain oil derivatives (Pene-
trol) (26) generally on the market in Florida, the nicotine can
be reduced to about half of that recommended above.
LARGE PLANT BUGS
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 varieties of citrus having thin skins suffer most. Tan-
gerines, including satsumas, are the first choice of the bugs,
.and oranges second. Grapefruit is not much troubled.
SOUTHERN GREEN STINK BUG OR PUMPKIN BUG
Nezara viridula Linn.
The pumpkin bug or green stink bug is by far the most com-
mon and destructive of the large plant bugs. It breeds particu-
larly on such legumes as cowpeas and beggarweed and when
these are grown as a summer cover crop in the groves and al-
lowed 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 1/2 inch long and
slightly more than half as wide, being broadly oval in outline.
(Fig. 62.) The males are a little shorter and considerably
narrower, on the average.
The young (Fig. 60) are quite different in appearance from
the adults. They are bluish with some red markings and are
more nearly circular in outline. Like all members of the "stink
bug" family, to which they belong, pumpkin bugs give off a
strong, disagreeable odor.
96 Florida Cooperative Extension
Fig. 60.-Light and dark colored forms of the southern green stink bug (Nezara viriduda),
fifth instar, enlarged about 4 diameters. (After Jones, Bull. 689, U. S. D. A.)
Eggs of the pumpkin bug are laid in clusters on the food
plant (Fig. 61). Drake (8) found that they hatched in four or
five days in May.
The young feed to-
gether in groups
or colonies for
some time after
hatching. T h e y
require about 32
days to complete
times. After the
fifth molt they be-
come adults with
wings and repro-
ductive or gan s.
Fig. 61.-Eggs and nymphs of the southern green stink bug The adults live for
(Nezara viridula) showing gregarious habit during first instar.
Enlarged. (After Drake, 8.) several weeks; the
last generation in
the fall lives for several months. There are four or five genera-
tions a year. No breeding takes place during the winter, at least
in most of the state. Drake found the first eggs at Gainesville
in April. At Gainesville hibernation is only partial. Although
many may be found under the bark of logs, Spanish moss, and
other sheltered places where they apparently remain until the
return of warm weather, others in constantly decreasing num-
Citrus Insects and Their Control 97
bers, remain on juicy plants and are more or less active and
feed all winter. They
are abundant in Octo-
ber, plentiful in No-
vember, common in
December, but rather
scarce in January and
February. In March
and April they again
become more common
due to many bugs com-
ing out of hibernation.
In April and May
Fig. 62.-Southern green stink bugs. Natural size.
In spite of their bad
odor, birds occasionally eat these bugs. They are also attacked
by other bugs, one of the most important being Euthyrhynehus
Sfloridanus (Fig. 63). The most efficient check
Son their increase are tachinid flies (Fig. 64)
whose larvae live as parasites inside of the
bugs. Eggs (Fig. 65) of this fly are laid on
the backs of the bugs. Upon hatching the
grub bores through the hard covering of the
L. bug and enters its body where it lives for
from two to three weeks (8). After attain-
ing full growth the maggot leaves the body
Fig. 63.-Euthyrhachus of the host, which is usually dead by this time,
Fig. 64.--a, adult male and b, female taehinid fly (Trichopoda pennipes). Enlarged.
(After Drake, 8.)
98 Florida Cooperative Extension
at the posterior end and enters the ground to pupate where it
remains for about 12 days, after which the adult fly emerges.
These flies feed on the nectar of flowers and can be seen hover-
ing about flowers any month of the year, although inactive
during the coldest days of winter.
Because of their large size no spray safe to use on citrus
trees will kill the adults. The larvae may be killed by the oil
-.1 or tobacco solu-
tions. Even if
there was a safe
would kill these
bugs it would be
to spray than to
collect the adults
from the fruit.
For this purpose
large nets. (Fig.
66) at least three
feet in diameter
and. of equal
depth should be
made. Muslin is
a good material
from which to
make these nets.
Each net should
Fig. 65.-Adult of Southern green stink bug (Nezara viridula) have a short han-
bearing eggs of a taehinid parasite (Trichopoda penniess. die which if ex-
Enlarged. (After Drake, 8.)
tended across the
diameter to stiffen the opposite rim will permit the use of tele-
phone wire to complete the skeleton for the net. Bend the wire
into a loop and nail the loose ends to a wooden handle.
One man can manipulate this net, but two may work to better
advantage. One places the net under a limb of fruit and the
other gives the branch a quick, vigorous shake which causes the
bugs to roll into the bottom of the net. After the men have
finished a tree the bottom of the net is dipped into a bucket
Citrus Insects and Their Control 99
containing kerosene. This keeps the net constantly wet with
In one grove of 10-year-old trees set 20 to 30 feet the work
cost between 50 and 75 cents an acre, and from 30 to 100 bugs
per tree were collected. Two men with a net covered at least
an acre in two hours. On larger trees with more bugs the cost
is greater, but should in no case exceed $1.50 an acre-still
much less than the cost of spraying.
Fig. 66.-Type of net used in collecting pumpkin bugs from small citrus trees.
For large trees not too close together and with few limbs
touching the ground to prevent a ready manipulation, the nets
should be larger. The writers have used some nets 6 by 12
feet. These were suspended from a light wooden frame like
those used for holding quilts or stretching curtains, the net
sagging two or three feet in the center. The net should be of
closely woven canvas so that insecticide oil, crude oil or kero-