Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: A contribution to the biology and control of the green citrus aphid, Aphis spiraecola Patch
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Permanent Link: http://ufdc.ufl.edu/UF00026777/00001
 Material Information
Title: A contribution to the biology and control of the green citrus aphid, Aphis spiraecola Patch
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 429-476 : ill., charts ; 23 cm.
Language: English
Creator: Miller, Ralph L ( Ralph Lester ), 1902-
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1929
Copyright Date: 1929
 Subjects
Subject: Spirea aphid   ( lcsh )
Spirea aphid -- Control   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 474-475).
Statement of Responsibility: by Ralph L. Miller.
General Note: Cover title.
General Note: Originally presented as: Thesis (Ph. D.)--Ohio State University.
 Record Information
Bibliographic ID: UF00026777
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltuf - AEN4061
oclc - 18175462
alephbibnum - 000923510

Full Text





HISTORIC NOTE



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
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida







Bulletin 203 April, 1929



UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
Wilmon Newell, Director







A CONTRIBUTION TO

THE BIOLOGY AND CONTROL OF THE

GREEN CITRUS APHID,

Aphis Spiraecola PATCH

By RALPH L. MILLER









TECHNICAL BULLETIN






Bulletins will be sent free upon application to the
Agricultural Experiment Station
GAINESVILLE, FLORIDA

*








BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola FRANK J. WIDEMAN, W. Palm Beach
E. W. LANE, Jacksonville J. T. DIAMOND, Secretary, Talla-
A. H. BLANDING, Leesburg hassee.
W. B. DAVIS, Perry J. G. KELLUM, Auditor, Tallahassee

STATION EXECUTIVE STAFF
JOHN J. TIGERT, M.A..LL.D., President IDA KEELING CRESAP, Librarian
WILMON NEWELL, D. Sc., Director RUBY NEWHALL, Secretary
S. T. FLEMING, A.B., Asst. Director K. H. GRAHAM, Business Manager
J. FRANCIS COOPER, B. S. A., Editor RACHEL MCQUARRIE, Accountant
ERNEST G. MOORE, M. S., Asst. Ed

MAIN STATION-DEPARTMENTS AND INVESTIGATORS
AGRONOMY ECONOMICS, AGRICULTURAL
W. E. STOKES, M. S. Agronomist C. V. NOBLE, Ph. D., Ag. Economist
W. A. LEUKEL, Ph. D., Asso. BRUCE MCKINLEY, A.B., B.S.A., Asst.
C. R. ENLOW, M. S. A., Asst.* M. A. BROKER, M. S. A., Asst.
FRED H. HULL, M. S. A., Asst. R. H. HOWARD, B.S.A., Field Asst.
ANIMAL HUSBANDRY ECONOMICS, HOME
A. L. SHEALY, D.V.M., Veterinarian, OUIDA DAVIS ABBOTT, Ph. D.. Chief
in Charge L. W. GADDUM, Ph. D., Asst.
D. A. SANDERS, D.V.M., Asst. Vet. C. F. AHMANN, Ph. D., Asst.
E. F. THOMAS, D.V.M., Asst. Vet. ENTOMOLOGY
R. B. BECKER, Ph.D., Asso. in Dairy ET LY
Husbandry J. R. WATSON, A. M., Entomologist
C. R. DAWSON, B. S. A., Asst. Dairy A. N. TISSOT, M. S., Asst.
Investigations H. E. BRATLEY, M. S. A., Asst.
CHEMISTRY HORTICULTURE
R. W. RUPRECHT, Ph.D., Chemist A. F. CAMP, Ph. D., Horticulturist
R. M. BARNETTE, Ph. D., Asso. M. R. ENSIGN, M. S., Asst.
C. E. BELL, M. S., Asst. HAROLD MOWRY, Asst.
H. L. MARSHALL, M. S., Asst. G. H. BLACKMON, M. S. A., Pecan
J. M. COLEMAN, B. S., Asst. Culturist
J. B. HESTER, B. S., Asst. PLANT PATHOLOGY
COTTON INVESTIGATIONS W. B. TISDALE, Ph. D., Plant Path.
W. A. CARVER, Ph. D., Asst. G. F. WEBER, Ph. D., Asso.
M. N. WALKER, Ph. D., Asst. A. H. EDDINS, Ph. D., Asst.
E. F. GROSSMAN, M. A., Asst. K. W. LOUCKS, B. S., Asst.
RAYMOND CROWN, B.S.A., Field Asst. ERDMAN WEST, B. S., Mycologist

BRANCH STATION AND FIELD WORKERS
Ross F. WADKINS, M. S., Lab. Asst. in Plant Pathology (Quincy)
JESSE REEVES, Foreman, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
W. A. KUNTZ, A. M., Assistant Plant Pathologist (Lake Alfred)
J. FRANKLIN FUDGE, Ph. D., Assistant Chemist (Lake Alfred)
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle Glade)
R. V. ALLISON, Ph. D., Soils Specialist (Belle Glade)
L. O. GRATZ, Ph. D., Associate Plant Pathologist (Hastings)
A. N. BROOKS, Ph. D., Associate Plant Pathologist (Plant City)
A. S. RHOADS, Ph. D., Associate Plant Pathologist (Cocoa)
STACY O. HAWKINS, M. A., Field Assistant in Plant Pathology (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
R. E. NOLEN, M. S. A., Field Assistant in Plant Pathology (Monticello)
FRED W. WALKER, Assistant Entomologist (Monticello)

*In cooperation with U. S. Department of Agriculture.









A CONTRIBUTION TO THE
BIOLOGY AND CONTROL OF THE GREEN CITRUS
"APHID, APHIS SPIRAECOLA PATCH*
By RALPH L. MILLER,
Formerly Assistant Entomologist, Florida Agricultural Experiment Station

The purpose of this bulletin is to discuss in some detail the
life history and habits of the green citrus aphid now commonly
found in Florida. Special attention is given to the control ef-
fected by the natural enemies-predators, parasites and fun-
gous diseases.
Most of the common insecticides available in Florida were
used experimentally. All previous publications concerning this
insect were reviewed and a bibliography is given at the end of
the paper.
The work was carried on at the Citrus Experiment Station at
Lake Alfred, Florida, and was a cooperative enterprise between
the Florida Agricultural Experiment Station and the State Plant
Board.
ACKNOWLEDGMENTS

The writer is indebted to Professor J. R. Watson for his direct
supervision and Dr. Wilmon Newell for his many suggestions in
regard to the problem. Dr. Herbert Osborn and Dr. R. C.
Osburn, both of Ohio State University, offered many helpful
criticisms of the work and the paper. Several men in the Bu-
reau of Entomology, United States Department of Agriculture,
aided by obtaining the analysis of materials and identifying in-
sects. Many thanks are due the wife of the writer for her aid
in preparing the paper for publication.

IDENTITY OF THE APHID

The identity of the green citrus aphid of Florida has been
somewhat obscured by a question of synonomy. In 1914, Dr. E.
M. Patch (13)' reported the following-"Aphis spiraecola n.n.
This species is certainly close to pomi and may possibly be a
variety but it does not seem safe to place it with that species at
present. It is recorded by Professor Gillette as Aphis spiraeela
*Presented in partial fulfillment of the requirements for the degree of
Doctor of Philosophy in the Graduate School of the Ohio State University.
Numbers in parentheses (italic) refer to "Literature Cited" in the
back of this bulletin.







432 Florida Agricultural Experiment Station

Schouteden 1910. The antenna is practically the same as with
pomi. The cornicles in the winged form are shorter than any
pomi I have taken."
The report of Professor C. P. Gillette (8) of which Dr. Patch
speaks is as follows-"Aphis spiraeella Schouteden Fig. 14 and
15. What I have taken to be this species was a very common
louse upon bridal wreath (Spiraea prunifolia). Taken at Lan-
sing, very abundant, Geneva, Detroit, Albany, New York City,
Washington, Springfield, Webster and Woods Hole. In general
appearance resembling closely a small A. pomi, was common one
year, 1907, on spiraea on the campus of the Agricultural Col-
lege at Fort Collins but has not been seen in the state since. The
antenna is hardly distinguishable from pomi except in size."
Professor J. J. Davis (6) considers Aphis spiraeella as found by
Professor C. P. Gillette different from Aphis spiraea of H.
Schouteden (16).
In 1923 Dr. Patch (14) reported the following-"My own
present interpretation of the situation is that we are concerned
with one very variable species. That Spiraea and not Pyrus was
the original primary food plant of the species; that the normal
cycle is still followed with reference to Spiraea; that Pyrus with
its succulent succession of summer growth (water sprouts, etc.)
and its normal overwintering habit has proven satisfactory
enough to serve as an all year host; and that the species in the
sexual generation is dimorphic, the rather degenerate forms on
the apple (with the wingless male) being the modification in
the apple race in the sexual generation."
In 1924 Dr. A. C. Baker is reported by Professor J. R. Wat-
son (22) as identifying the green citrus aphid as Aphis spirae-
cola Patch. In 1925 Mr. A. N. Tissot (19) transferred Aphis
pomi from apple in Pennsylvania to citrus in Florida and suc-
ceeded in getting only 2 of 47 to live to maturity and reproduce
while a similar number of the introduced aphids all developed
and reproduced abundantly on apple in Florida at the same time
and under the same conditions. He states that this may be evi-
dence that the citrus aphid is a new physiological race.
The points on which Dr. Patch separates the two forms are
sufficient in the minds of many workers to make the aphids dis-
tinct species. Since the two forms are not identical the green
citrus aphid is being called Aphis spiraecola Patch in this paper.








Bulletin 203, Biology and Control of Citrus Aphid 43.

It is hoped that further work on the biology of this aphid being
carried on at Gainesville, Florida, by Mr. A. N. Tissot will aid
in definitely settling the matter.

HISTORY AND DISTRIBUTION

Professor J. R. Watson (20) states that "this aphid first at-
tracted attention as a citrus pest during the spring of 1923, al-
though it was not until a year later that it was distinguished
from the melon aphid. However, its presence in certain groves
in the Manatee section as early as the fall of 1922 has been quite
definitely established. There is no sure record of its presence
on citrus in Florida at an earlier date. There are many records
of earlier infestations of aphids but usually such expressions
as 'the aphids left the citrus and went to watermelons,' would
indicate that the species involved was the melon aphid."
As to the spread of the aphid over the state Professor Watson
(29) states that it did not seem to follow the main lines of
transportation but rather followed the direction of the prevail-
ing winds. This shows that it was not carried so much by ve-
hicles as it was blown by the winds that occur almost continu-
ously. This aphid is now found in northwestern Florida and has
been reported from California by Mr. W. W. Others (31).
Specimens were received from Alabama by Professor Watson
in 1926. Mr. R. L. Westmoreland has recently reported it from
Honduras where growers say it has been present for at least
10 years. This aphid was recently reported from Cuba by Wat-
son (26) and has apparently been there also for some time.

HOST PLANTS

From time to time workers have given host plants for the
citrus aphid until at present there is a very extensive list.
Among the plants reported by Dr. Edith M. Patch (14), consid-
ering Aphis pomi and Aphis spiraecola identical, are the follow-
ing:
Polygonum lapathifolium L. ..............................Smartweed
Polygonum sachalinense Sacaline ..................- Smartweed
Rumex crispus L. ...............................................Yellow dock
Chenopodium album L ........................................Lamb's quarters
Portulaca oleracea L. .............-.......-................Common purslane
Ranunculus acris L .........----------....................----Buttercup
Capsella bursa-pastoris L. ---................................Shepherd's purse
Nasturtium palustre L. ........................................Marsh cress








434 Florida Agricultural Experiment Station



















a t
-. -



A e 7












Fig. 107.-Some hosts of the citrus aphid-
A. Spiraea sp., bridal wreath. This ornamental shrub furnished aphid
food during the entire year.
B. Citrus sp. Aphids were found on this host during the entire year.
However when groves had periods of complete dormancy no aphids were
present.
C. Pyrus malus, Apple. Like citrus, the apple is attacked whenever
new growth is present, but especially during the spring months.
D. Gnaphalium sp., cudweed (several species). This plant grows dur-
ing the period when citrus trees are dormant, November to April, and is
important in carrying the aphids over the winter.
E. Antigonon leptopus, coral vine, Rosa-de-Montana. This beautiful
vine grows during the entire year, if not killed by frost, but is attacked by
the citrus aphid only during the summer and autumn.









Bulletin 203, Biology and Control of Citrus Aphid 435

Raphanus raphanistrum L. ............................ ..Wild radish
Philadelphus coronarius L .........-...-- ..................Syringa or mock orange
Philadelphus grandiflorus Willd ..................
Ribes sp ........................ ..........-------Gooseberry
Amelanchier canadensis L. .........---.....-........--......--....-Shad bush
Pyrus aucuparia L. .........................-----............. Mountain ash
Pyrus communis L ...............................------........-- -Common pear
Pyrus japonica Thumb ................--------..................Japan quince
Pyrus malus L. ...........------ ...---.------Common apple
Spiraea aruncus L. .........----... --------..Goat's beard
Spiraea prunifolia Sieb. ..........-....-... ..-....---Bridal wreath
Spiraea salicifolia L. .........---------...--Meadow-sweet
Spiraea van houttei .....---......----. -----......
Pisum sativum L .................... ......--- .......-.--- Common pea
Trifolium pratense L. ....--.......--------.. ----...Red clover
Impatiens balsamina L. ....... ..-----------.... Garden balsam
Celastrus scandens L............-----................--..----.Bitter-sweet
Rhamnus cathartica L........................--..............Common buckthorn
Ampelopsis quinquefolia ..............-------....................Virginia creeper
Malva rotundifolia L -------................................------Common mallow
Aralia racemosa L .... ---................--..................--Spikenard
Daucus carota L ....-- --....................................--- Wild carrot
Comus amomum Mill.................................-----..Silky cornel
Comus sericea L. ...............---... --. ------
Comus stolonifera Michx ..............------............---------Red-osier dogwood
Forsythia suspense Vahl. ...........-----------
Ligustrum ibota Sieb..........----------.. ..---
Apocynum androsaemifolium L ...............-.....-..Spreading dogbane
Asclepias cornuti Dcne. -.---- ---------.Common milk weed
Galeopsis tetrahit Linn. ....-------...............................Common hemp nettle
Plantago major Linn. .... ---.......-----.......... --.........Plantain
Sambucus canadensis L .......-------............. ...........---Common elder
Viburnum dentatum ........................--- ...-------- .. Arrow-wood
Viburnum opulus var. americana ..-...........-.......Highbush cranberry
Eupatorium perfoliatum L...........................---.....Thoroughwort, boneset
Eupatorium purpureum L .......---------........................Joe-Pye weed
Leontodon autumnalis L. ...........---......................Fall dandelion
Matricaria matricarioiles P .......---------.....................Common sow-thistle
Taraxacum officinale Weber .......-------......................Common dandelion

In Florida this aphid has been reported from the following
plants:-
Citrus sp. ......................................------ -All citrus
Pyrus malus Linn. .. ----................... ...-....-- Apple
Pyrus communis L .............--------....................------Pear
Pyrus japonica Thumb. ..---------.............................Japan quince
Pyrus sp. --------.....................--....-------........ Sand pear
Spiraea sp ...... -- ...............- ........ .............. Bridal wreath (several sp.)
Asclepias tomentosa Ell ....................................Milkweed
Gnaphalium sp ................------.......-............ Cudweed (several sp.)
Solanum sp ......... -....................----..........Nightshade
Eupatorium capillifolium Small.........................Dog fennel
Chenopodium ambrosioides D. .....-.....................Mexican tea
Chenopodium album L ......................................Lamb's quarters
Sonchus sp. ........ ....................--...............Sow-thistle
Prunus sp ..........----....... ..------.....................-- Wild plum
Eriobotrya japonica Lindl. ................................Loquat
Lactuca sp. ................................--- ........---- Lettuce
Laurocerasus caroliniana (Mill.) Roem.) ........Cherry laurel
Pereskia aculeata Mill. ......... ..- ......Lemon vine









436 Florida Agricultural Experiment Station













II
11


































Fig. 108.-More hosts of the citrus aphid-
A. Chenopodium ambrosioides, Mexican tea. This plant serves as host
for the citrus aphid during the late spring and late autumn months.
B. Gardenia sp., night blooming jasmine. This ornamental is an occa-
sional citrus aphid host plant but is attacked most severely during the
spring.
C. Amaranth sp., red root or pigweed. This common weed is occasional-
ly found with a very light infestation of aphids during late spring.
D. Pisidium guayava, guava. Citrus aphids are occasionally found to
feed on this plant but do not seem to thrive on it.
E. Asclepius tomentosa, milkweed. This common grove weed grows
during the spring and is attacked by the aphid during late spring and
early summer.
F. Pereskia aculeata, lemon vine. Occasionally attacked.









Bulletin 203, Biology and Control of Citrus Aphid 437










































Fig. 109.-Other hosts of the citrus aphid-
A. Cryptostegia grandiflora, rubber vine. During late spring this orna-
mental is often severely attacked by the citrus aphid.
B. Bidens leucantha, Spanish needle. The flowers and flower stems of
this common weed are very severely attacked during late spring or fall.
C. Eupatorium capillifolium, Dogfennel. Occasionally attacked.
D. Rumex crispus, yellow dock. This plant grows during the spring
and is an occasional aphid host.
E. Phytolacca decandra, pokeweed. Although the writer was not able
to rear a complete generation of aphids on this plant, young were often
deposited on it.










438 Florida Agricultural Experiment Station


Phytolacca decandra L. ..................... ...........Pokeweed
Erechtites hieracifolia L ...............................Fireweed
Malus angustifolia (Ait.) Michx. ...................Crab apple
Persea persea (L) Cockrell ...............................Avocado

The writer has taken the citrus aphid from the following addi-
tional host plants in Florida:-
Amaranthus sp. .... ...............................................Amaranth, careless weed
Rumex crispus L. ...................... ......................Yellow dock
Rumex acetosella L. .............................................Horse sorrel
Antigonon leptopus Hook and Arn .................Coral vine, Rosa-De-Montana
Cryptostegia grandiflora R. Br. .....................Rubber vine
Bidens leucantha L. (Willd.) ..........................Spanish needle
Gardenia sp. ...................................... ..... Jasmine
Psidium guayava ..............................................Guava

In the case of citrus trees only very young growth is attacked;
that is, growth under three weeks of age. In the case of other
plants there is not as much preference shown but leaves and
especially flowering heads are attacked. Most host plants, ex-
cept spiraea, seem to be temporary or overflow host plants.


Citrus sp. A....................... E. 1 ARIAY TUNE uLY Aug. :S1t. t Ho DeC..

Spiraea sp. ..........

Gnaphalium sp. ..............
(Cudweed)
Rumex crispua ...............
(Yellow dock)
Antigonon leptopu..........
(Coral vine)
Pyrus malus ...........
(Apple)
Gardenia sp......................
(Jasmine)
Bidens leucantha............
(Spanish needle)
Aselepias tomentosa.........
(Milkweed)
Phytolacea decandra........
(Poke weed)
Erechtites hieracifolia.....
(Fire weed)
Chenopodium ambrosi
oides (Mexican tea)
Rumex acetosella ............
(Sheep sorrel)
Cryptostegia grandiflora
(Rubber vine)
Amaranth sp. ...............
(Careless weed)
Psidium sp ..........................
(Guava)

Fig. 110.-Seasonal host plants of the green citrus aphid.








Bulletin 203, Biology and Control of Citrus Aphid 439

They are attacked only when the aphids become concentrated
on citrus and must leave because it hardens. In Figs. 107, 108
and 109 are shown a group of the most common aphid host
plants.
Fig. 110 shows the seasonal host plants of the citrus aphid.
This is based on weekly observations made at Lake Alfred,
Florida. A plant was considered a host when the adult had de-
posited young thereon or when only young were found.
Table I shows the life history of Aphis spiraecola on various
host plants. Mature females, taken from citrus, were allowed
to deposit young, the adults were removed and the young ob-
served until death. All life history work was carried on in cloth
bags in the nursery or grove and representative individuals
were chosen in each case.
VARIETIES OF CITRUS ATTACKED
When the aphid first appeared it was the opinion of many
growers and workers that the tangerine and the Temple orange
were the choice of all citrus host plants. Further work and ob-
servations have indicated that this is not entirely true. The
aphid can live and reproduce quite well on grapefruit which was
at first thought to be immune from attack. The tangerine is
most severely attacked because it grows continually and later
in the spring. It is just beginning to grow well when orange
and grapefruit growths begin to harden. For this reason the
winged aphids leave the hardening growth only to concentrate
on the tender, succulent tangerine and cause severe damage.
Grapefruit is not attacked, for it grows quite early, hardens its
growth quickly and then remains dormant. If for some reason
grapefruit grows late in the spring or otherwise out of season
it may be severely attacked. During the spring of 1927 follow-
ing the freeze many grapefruit groves in the vicinity of Lake
Alfred were growing irregularly and these were quite severely
attacked by aphids.
Instead of naming varieties that are severely attacked one can
say that any variety which grows continuously and late in the
spring will be severely attacked. Those which harden their
growth early in the spring are not attacked. For example, the
continuously growing Temple orange is almost always infested
while grapefruit is very seldom attacked. Rough lemon, and es-
pecially sour orange and trifoliata trees are only slightly at-
tacked. Kumquats are not attacked.







TABLE I.-EFFECT OF DIFFERENT HOST PLANTS ON THE LIFE HISTORY OF Aphis Sprraecola PATCH.
b-born; v-development; numbers-young deposited; d-died.

S rs g -g

|I I 1C






1 b b b b b b b b b b b b b b b
2 v v vv v v v v v v v v -----
3 v v v v v v v v v v v v v v
4 v v v v v v v v v v v v v v ........ v
5 v v v v v v v v v v v v d d I v
6 3 v v v v v v 5 ....... .. ..... v

8 4 4 3 6 v v 1 3 v 1 1 v 6 ............. v
9 8 1 4 4 2 2 1 1 v 1 2 v 8 ---------- ----- -
10 2 3 4 1 3 1 2 1 0 1 1 10 -------- ... .... 1



11 12 2 3 7 3 1 3 2 2 d d 1 -- ......... ....- .... 0

12 8 0 2 4 3 1 3 0 2 .......... 1 5 ......... ...... .
13 6 5 3 7 2 1 4 1 1 : -- d 3 -- ---- 2
14 4 2 4 4 0 2 1 d 0 2 .. --- --- -- 0
16 8 1 1 9 .......... 0 3 .... .. ..... - --- _1 d -.
17 1 2 1 1 _._ .... 0 3 ... .. -- ----. - t - - - -
. .da y s I I |. . .. . ------I I | | | I ~ -












186 2 v v v v v v v v v v .v 5 ---------- --



2 1 -- -- d .. ... ... . .. : : : : : : : : : : : : : : : : : : ::-- -.-
9 All 1 died in three attempts.
14 4 2 4 4 0 2 1 d 0---------- 2 *- -
16 8 1 1 9 0 3 I d .
17' 1 1 2 1 1 0 3 3---- ----- --- -- --- .1-.-- ........1 I...... --....-
18 d 1 1 2 d 0- |-.-- .-.-- .- .- --i--.-...-. .... .. ----
19 5 d 1 d .... . 1.. .1- -..-. I - - -
20 0 0 .00... .. l.. i
22-1 - 1------------------ 0 d -- -- ---- ...-....-...------------i.-.-- |
23--------0----------------- -------I--------- ----I ----I------------------


24 diedd in- te------ -----------------









Bulletin 203, Biology and Control of Citrus Aphid- 441

DAMAGE CAUSED BY THE CITRUS APHID

The most noticeable damage of the citrus aphid is that of leaf
curling. One or two aphids feeding on the underside of the leaf,
as is their habit, will cause it to curl slightly, while a larger num-
ber will cause it to curl tightly. After a leaf has been curled
it loses its oily appearance and appears dwarfed. A tree with
many such leaves seems greatly stunted. (See Fig. 111.) This
curling causes the leaf surface to be reduced or of poor quality
for carrying on the necessary processes. It causes a small weak

TABLE II.-EFFECT OF APHIDS ON TANGERINE BLOSSOMS AND YOUNG FRUIT.

Severely Attacked by Aphids Free From Aphids
Blossoms Fruit Set Blossoms Fruit Set

3 0 15 4
3 1 16 2
5 2 4 0
7 1 10 3
10 1 13 1
11 0 5 2
2 2 2 0
16 1 7 1
4 1 10 5
3 0 16 1
10 2 10 4
19 2 14 2
17 0 3 1
11 1 7 2
5 0 6 0
3 0 ...

129 14 138 28

10.9% Set fruit 20.3% Set fruit








442 Florida Agricultural Experiment Station

bloom without any leaves to appear the next season. Curled
leaves on a tree afford a well protected hiding place for scale.
Most scale crawlers are negatively phototropic and hunt curled
leaves or similar dark places to attach themselves. Dr. F. R.
Cole (4) estimated that the citrus aphid caused four million
dollars damage to citrus during 1924.
When blossoms or very young fruit are attacked by aphids
much of the fruit will drop. Professor J. R. Watson states-"A
heavy infestation of aphids materially reduces or entirely pre-
vents the setting of fruit." Table II shows the effect of aphids
on tangerine blossoms and young fruit.
Damage caused by the citrus aphid appears to be only tem-
porary, for twigs with severely curled foliage will often produce
straight growth at the next flush if kept free from aphids. (See
Fig. 111.) Fortunately for the grower there is usually only
one flush of growth of the year that is severely attacked by
aphids.
LIFE HISTORY

Probably the first life history work in Florida on the citrus
aphid was done by Mr. A. H. Beyer (2) during the spring of
1924. He gives the following summary-"Viviparous females
were used in starting these studies as no eggs or stem mothers
were found. The reproductive period of the female varied, dur-
ing the time of these studies, from 2 to 11 days with an average
of five young per day. The longevity of the females used ranged
from 3 to 21 days. In most cases death was due to natural
causes. We must, however, take into consideration the condi-
tions of temperature and humidity which would have some in-
fluence on the mortality, as the experiments were conducted
under a tent where the temperature ranged from 85 to 98 de-
grees.
"The maximum number of young produced by a single fe-
male was 61 and the minimum was 8. The birth rate was high-
est in the early life of the female and the largest number of
young were brought forth during the morning hours. The per-
centage of winged individuals produced during this series of
experiments ranged from 45 to 69."
Mr. A. N. Tissot (18) working at Gainesville, Florida, and
rearing aphids out of doors in cloth bags (the type after which
the writer has patterned his), states that the development pe-
riod of the aphid ranged from 13 days in March to 6.7 days









Bulletin 203, Biology and Control of Citrus Aphid 443

in the first half of May. In November the average total young
produced per female was 34 while in April it was 70.8. The daily
rate of reproduction was 2.7 young per female in November
and 4.1 during April. He also states that the aphids develop
better at the temperature during April but do not develop as
well at higher or lower temperatures.

















R 8




















Fig. 111.-Showing damage by citrus aphid, and materials used in life his-
tory work. A. Normal citrus leaves. B. Badly curled citrus leaves. C.
Damaged twigs showing new growth. D. Twig of tender, susceptible
growth. E. Bags used in life history work. F. Nursery used in life his-
tory work.










444 Florida Agricultural Experiment Station


Beginning in August, 1926, the writer began a first born
generation series life history study of Aphis spiraecola. This
work was carried on entirely out of doors. The aphids were
caged in cloth screen bags on tender growth of nursery trees.
(See Fig. 111.) Very tender citrus twigs were used as host
plants during the entire year except immediately after the
freeze in January, 1927, when they were not available. At this
time spiraea was used and as soon as growth appeared on the
citrus the aphids were again placed on that.

lirst born generation. .....Last born generations.
No. of Jan. I Feb. I Mar. Apr. May. Jun.I Jul.1 Aug.1 Sep. I Oct. Nov. Dec.
Oenera- I I I
lione I I


... .. I | I I
2
43 -. -
5 ... I
6 ... I '.......




17 I I
98 ..



9 --
13 I _I .





21 --
14
15
17 7=

20 1
22 1
23
24 1


28
29 9
30



31
32
33

36
38 -
39
41



Fig. 112.-A record of the aphid generations which occurred in a study
at Lake Alfred, Florida, from August, 1926, to July, 1927.

To begin the work, a robust wingless female was chosen. Her
first born young were allowed to mature in captivity. At their
maturity one was chosen and its first born were again reared
to maturity, etc. The last born generations are not complete









Bulletin 203, Biology and Control of Citrus Aphid 445


records of one individual but when the last born of one indi-
vidual were produced another generation was begun, which
method gave a series of last born generations extending over
the entire year.

TABLE III.--VARIATION IN MATURITY, REPRODUCTION AND LENGTH OF LIFE
OF APHIDS.

b-born; v-developmental period; numbers-young produced; d-died.


Days CS P 0 '


1 b b b b b b b b b b b b
2 v v V V V V v V v i v
3 v v v v v v v v v v v
4 v v v v v v v v v v v v
5 v v v v v v v v 7 v v v
6 vv v v v V v v 6 v v v
7 v v v v v v v v 5 v v v
8 v v v 5 v v 3 2 5 3 v v
9 v v v 5 6 v 3 0 11 0 3 5
10 v v v 9 4 3 2 0 5 3 6 5
11 v v v 3 3 0 0 1 5 1 2 6
12 v 7 4 1 4 d 1 d 7 6 0 6
13 v 4 3 1 .. 3 ... 1 1 5 6
14 v 5 3 6 5 ...... 2 ....... d 4 4 5
15 v 6 6 1 4 ... 0 ........- ... 4 0 4
16 1 5 7 1 d ............ 3 4 5
17 0 5 3 4 3 -....-.......... ......- 0 6 3
18 0 6 8 0 0 ...... .. .... ....... d 3 7
19 0 0 8 2 4 .. ..... ...... ......... 2 6
20 2 3 6 2 1 ... .. ...................... 1 4
21 1 4 5 0 4 ....... .. .....0........... 6
22 1 5 6 1 2 ... .... ...-.. .. ....... 1 4
23 5 7 1 0 0 ..... .... ........ .... 1 1
24 0 6 d d 0 ........0.. ...... ... ..... 2
25 1 3 ...2..... ... 0 ... ........ ..... ....... 0 2
26 2 d ...... d ... ................ 0 0
27 3 ... ....... ..... .... ..... ............... 0 2
28 3 --...-- ..-- ...- -....-- -. ....- . ... .-........ 0 0
29 2 -...... ............ ........ ...-.. ...... 0 0
30 1 ... ...... . ........ ... .. -- ............ d 0
31 2 ..... ........ ..... ........... .. ........ ... 0
32 2 .......................... ........ .... 0
33 0 ... .... ............... ........... ............ 0
34 0 ........ .................................. d
35 0 ................ ....... .... ..... ........
36 3 ................... --
37 0 ....................
38 1 .. .....................
39 0 ..... .........1....
40 d .. .. ....... ..... .. .. .. .. .
_ _ _I I I ----- -----_ _
There is considerable variation in the time to mature, rate
of reproduction, length of life and total number of young pro-







446 Florida Agricultural Experiment Station

duced during different times of the year as shown in Table III.
Representative individuals born each month were chosen.
As will be seen from the life history work the aphid passes
the entire season in the active stage at Lake Alfred, Florida.
So far as the writer has been able to ascertain, no male forms
or oviparous forms appear and no eggs are deposited. At Gaines-
ville, Florida, eggs were deposited rather abundantly on spiraea.
Mr. A. N. Tissot (18) found in 1925-26 that these eggs did not
hatch while in 1926-27 many hatched quite successfully. No
eggs were ever found on citrus.
Nymphal Period.-The nymphal period was quite variable
during the year. It was shortest during the month of Septem-
ber (4 days), and longest during the months of January (16
days), and June (13 days). The average for the year was 6.93
days for 198 females.
Reproduction.-The highest rate of reproduction occurred in
September. An average of 7.3 young per day per female oc-
curred during the week of September 13 at an average tempera-
ture of 790. Another point of high rate of reproduction was
reached in February when an average of 6.8 young per female
per day was found during the week of February 14 at an aver-
age temperature of 700. The lowest rate of reproduction was
found during January but reproduction during the remainder
of the year, with certain exceptions, was quite low also. The
daily reproduction for the year was 2.98 young per female. The
greatest number of nymphs deposited on one day by one female
was 16. The total number of young produced by one female
was quite variable, ranging from 1 to 103. The average number
of young produced per female for the year was 29.11 for 198
females.
Number of Generations.-From August 18, 1926 to August
17, 1927 the citrus aphid was reared through 44 successive first
born generations and 20 successive last born generations. The
average number of young produced by females in each genera-
tion was quite variable, ranging from 71.6 in the 21st genera-
tion in February to .8 for the 37th generation in June.
Longevity.-The length of life was found to range from an
average of 11.8 days during late May or early June to 33 days
during January. The greatest length of life known was 49 days.
The average length of life for 198 females during the year was
36.7 days.










Bulletin 203, Biology and Control of Citrus Aphid 447

Life History of Winged Forms.-There is usually a difference
in the life history of winged forms for in most cases the nymphal
period is longer and the rate of reproduction somewhat less than
that of the wingless forms.

TABLE IV.-LIFE HISTORY OF WINGED AND WINGLESS APHIDS.
b-born; v-developmental stage; numbers-young produced; d-died.

Days Wingless Females Winged Females
of the
Month November March November March

1 b b b b b b b b
2 v v v v v v v v
3 v v v v v v v v
4 v v v v v v v v
5 v v v v v v v v
6 v v v v v v v v
7 v v v v v v v v
8 v v 2 3 v v v v
9 v v 3 4 v v v v
10 v v 4 5 v v v v
11 v v 8 5 v v 4 4
12 v v 5 7 v v 0 5
13 v v 12 2 v v 0 0
14 2 2 8 9 v v 2 1
15 6 5 6 8 v .v 1 3
16 5 3 4 4 v 2 3 3
17 8 5 5 5 v 2 3 2
18 5 8 8 5 1 4 4 1
19 5 5 d 5 3 4 4 5
20 5 5 .............. 0 1 3 2 4
21 12 4 ............ 4 7 4 2 2
22 4 3 .............. 1 5 0 6 1
23 6 5 .............. 2 0 0 0 6
24 8 6 .............. 0 1 1 3 4
25 8 3 ............. 0 d 0 3 1
26 4 5 .............. ..0 ... 4 4 d
27 4 3 -..........i 0 .............. 4 d
28 4 4 .............. 0 ............. 4
29 3 1 .............. 0 .............. 0 ------- ....- .......-..
30 1 d ........-.... d .d I........- .....
31 d -............. .............. ........ ..... .. ..... --- -----......... ....... .


OCCURRENCE OF WINGED FORMS

Observations made during the year showed that winged
aphids were always present; however they were most abundant
during late April and May. Whenever one could find a tree grow-
ing continuously or a tree with hardening growth, he was sure
to find a few winged aphids present. This observation led the
writer to believe that the development of winged forms could








448 Florida Agricultural Experiment Station









.- .. *. ..












B D









Fig. 113.-Apparati used in testing reactions of the citrus aphid-
A. Phototropic apparatus. The top of the trough was covered with
various grades of material as follows: open, wire screen, single cheese
cloth, single sheeting, double sheeting and cardboard. Water was run over
the tube to maintain a constant temperature.
B. Humidity apparatus. The test tubes contain various grades of sul-
phuric acid from pure to water.
C. Thermotropic apparatus. The heat was generated by the alcohol
lamp and salted ice was used for the low temperature. This apparatus was
set up in a dark room.
D. Chemotropic apparatus. Aphids were liberated in the center of the
circle and the whole apparatus was set up level in the dark room.








Bulletin 203, Biology and Control of Citrus Aphid 449

be correlated with abundance or kind of food, so the following
counts were made.
During the process of rearing aphids for life history work
through an entire year few winged forms appeared. It was ob-
served however that when a large number of young aphids were
allowed to mature on one rather hard twig, many winged forms
appeared but when some from the same lot were allowed to ma-
ture singly on tender foliage they were always wingless.
Of 198 aphids produced by wingless stem mothers and reared
to maturity singly on tender foliage, 190 were wingless and 8
winged. Of 238 aphids produced by wingless stem mothers and
reared to maturity in a group on one partly hardened twig, 152
were winged and 86 were wingless.
Seven young, deposited by a wingless female on a tender cit-
rus leaf 1 x 2 cm., matured as wingless females, while of 30
aphids from the same female, placed on a leaf of similar size
and condition, 22 matured with wings and 8 were wingless. As
indicated in the examples above, it seems that the crowding of
aphid nymphs during development causes the production of
winged forms. Twenty aphids deposited by winged females
were allowed to mature singly on tender foliage and all were
wingless. Aphids reared on Bidens levcantha, Rumex crispus
and Eupatorium capillifolium produced many winged forms,
while those reared on Pyrus malus and Erechtites hieracifolia
produced only occasional winged forms.

REACTIONS OF THE CITRUS APHID

Geotropism.-When aphids were scattered over the inside of
a one-inch glass tube, two feet long, stoppered at both ends and
the tube hung in a vertical position in a dark room, they gave no
marked reaction. When all of the aphids were placed at the bot-
tom of the tube a count three hours later showed that many had
crawled to the top.
Phototropism.-When aphids were scattered over the inside
of a glass tube (placed under running water at 850 F.) part of
which was unshaded, part shaded by 24 mesh copper wire screen,
part by cheesecloth, part by unbleached sheeting, double sheet-
ing and cardboard, the aphids left the darkness under the card-
board and the bright light in the open to become markedly more
concentrated under the cheesecloth. See Fig. 113. This experi-
ment was conducted out of doors between the hours of 1 and









450 Florida Agricultural Experiment Station

5 P.M. on July 10. The sun was very bright. Table V shows the
reaction to the various degrees of light intensity. The numbers
represent the actual number of aphids found at various places
in the tube as the experiment progressed.

TABLE V.-REACTION OF APHIDS TO LIGHT.
Material Used Inches 2:15 P.M. 3:45 P.M. 4:45 P.M. Total


Cardboard 1 69 10 11
(Almost total 2 37 8 8
darkness) 3 43 17 20
4 33 30 27 66

5 50 45 43
Double 6 50 75 68
Sheeting 7 61 60 63
8 51 55 55 229

9 47 53 43
Single 10 36 52 48
Sheeting 11 43 60 57
12 47 50 61 209

13 51 66 70
Cheese 14 40 91 96
Cloth 15 46 89 83
16 49 80 79 328

17 48 85 90
Screen 18 40 67 59
19 47 55 47
20 56 41 31 227

21 61 8 11
Unshaded 22 30 5 7
23 47 10 20
24 55 25 40 78

1137 1137 1137 1137

Thermotropism.-When aphids were distributed over the in-
side of a glass tube and this tube immersed in a water bath
varying in temperature from 640 C. at one end to 00 C. at the
other, the results were as given in Table VI.
The aphids became most concentrated at a temperature be-
tween 80.5 and 850 F. which corresponds quite closely with the
temperature of maximum production (790F.).








Bulletin 203, Biology and Control of Citrus Aphid 451

TABLE VI.-REACTION OF APHIDS TO TEMPERATURE.

Temperature Inches Distrbiond
64C (147F) 1 killed
3 The high temperature was
4 "
5 0 maintained by an alcohol
6 0
7 0 lamp and the low tempera-
8 1
9 5 ture by salted ice. The
34*C (93F) 10 4
11 8 temperatures were recorded
12 10
13 15 by the thermometers inside
14 15
15 12 the glass tube. The whole
22oC (72-F)I 16 8
17 7 apparatus was set up in an
18 6 absolutely dark room.
19 1
20 5
21 2
22 0
23 0
0OC (32oF) 24 0 _

Chemotropism.-In order to observe the reaction of the cit-
rus aphid to its various host plants the apparatus was set up
as shown in Fig. 113. The cardboard was 16 inches square and
the twigs were placed six inches from the center ring. An ap-
proximately equal weight of twig was used in each case. All
tests were conducted on a level shelf in the dark room. All
aphids were liberated in the central ring and observations were
made at various times later.
Table VII shows the percent of aphids on the various plants
at different times of observations. All stages and both winged
and wingless individuals were used with apparently similar re-
actions. It will be noticed that the total number of aphids on
the plants decreased as the plants wilted.
Thigmatropism.-When the citrus aphid was touched-with a
brush or the point of a stick it became nervous and began to
move about. When aphids were to be transferred from one
plant to another it was quite easy to get them to loosen their
beaks by stroking them on the side with a camel's hair brush.
Effect of Humidity.-Five test tubes were prepared, using dis-
tilled water in one and various dilutions of sulphuric acid to pure
acid. By this method various grades of humidity were obtained.









TABLE VII.-REACTION OF APHIDS TO DIFFERENT HOST PLANTS. -

arftr Aphids Orange Mecan Tangerine Guava Spiraea Poke Bidens Paper
Star On Plants Tea
A
1% 149 46% 1% 11% 11% 2% 12% 6% 11%
4 221 51 2 12 8 1 13 4 9
6 195 48 4 14 7 4 11 9 3
22 102 72 1 5 6 4 10 2 0

B
1% 135 32% 2% 12% 12% 5% 24% 10% 3% 0
4 191 28 2 13 8 15 20 10 4
6 148 30 8 20 6 6 20 7 3
22 78 43 3 28 6 6 5 9 0

C

1% 142 14% 4% 9% 20% 15% 30% 7% 1% i
4 158 17 5 18 17 19 18 6 0
6 214 18 2 10 9 44 12 3 2
22 88 50 3 26 7 4 7 0 3








Bulletin 203, Biology and Control of Citrus Aphid 453

Ten cc. of the proper mixture was put into each tube and a loose
cotton plug pushed down half-way in the tube. Aphids were then
placed on top of the cotton plug and a cork was used to close the
mouth of the tube. See Fig. 113. The results are shown in Table
VIII.
TABLE VIII.-REACTION OF APHIDS TO HUMIDITY.

H I I Number Aphids Dead at End of

a 4W W Z w
0 eo og

Water 100 125 0 0 0 50% 75% 100%
1 85% 125 0 35% 85% 95% 100%
S38% 125 15% 50% ( 90% 100% ......
"% 4% 125 25% 75% 95% 100%

Acid
(conc.) 0% 125 75% 100% ....


No aphids lived more than 48 hours, but those in 100 percent
humidity lived three times as long as those in 0 percent hu-
midity.

INSECTS FEEDING ON HONEYDEW

Among the insects found associated with the citrus aphid is
a group that feeds on the honeydew and has no effect on the
aphid itself other than helping to keep the colony in a sanitary
condition. The following list of insects comprises those taken
by sweeping twigs quite heavily covered with honeydew.

Diptera- (Flies)
Cochliomyia macellaria Fab. Screw worm fly
Tropidia albistylum Macq. Syrphus fly
Musca domestic Linn. House fly
Graphomyia maculata Scop.
Tabanus americanus Forster Horse fly
Volucella esuriens Fabr.
Sarcophaga bullata Parker Flesh fly
Sareophaga helicis Towns. Flesh fly
Sarcophaga sp. Flesh fly








454 Florida Agricultural Experiment Station

Coleoptera- (Beetles)
Stephanucha areata Fabr.
Euphoria sepulchralis Fabr.
Cyphon variabilis Thunb.
Monocrepidius vespertinus Fab.
Mordellistena comata Lee.
Hymenoptera-(Wasps and Ants)
Vespula carolina Linn. Red wasp
Polistes pallipes Lep. Red wasp
Stictia carolina Fabr.
Sceliphron caementarium Drury Mud dauber
Solenius (Hypocrabro) decemmaculatus Say
Hoplisus (Hoplisoides) sp. near denticulatus Pack.
Tachytes sp.
Dasymutilla vesta Cress. Velvet ant
Dasymutilla occidentalis L. Velvet ant
Solenopsis geminata Fab. Ant
Componotus abdominalis floridanus Buckley-Ant
Camponotus socius Roger Ant
Dorymyrmex pyramicus var. flavus McCook-Ant

NATURAL AGENCIES TENDING TO CONTROL
THE CITRUS APHID
Meteorological Factors.-In many instances when trees are
heavily infested with aphids a dashing rain will wash great
numbers of them to the ground where they will be destroyed
(27). This is especially true when the rain is accompanied by
a wind. During the hurricane of September, 1926 many groves
in the vicinity of Lake Alfred were almost entirely freed of
aphids. The washing of the rain and the whipping of the wind
knocked the aphids off and killed them.
A temperature of 260 F. did not kill citrus aphids in the field
but all new citrus growth was killed and the aphids starved. Dur-
ing the hot weather in May, 1927, when a temperature of 103"
F. was reached the aphids died quite young. This condition of
temperature was probably made more severe by the accompany-
ing drought.
Cultural Factors.-Any method or time of cultivation, prun-
ing, irrigation, drainage or fertilization that causes the citrus
trees to grow continuously will allow the aphids to grow and re-
produce continuously and attack all new growth as soon as it
appears. Growers should endeavor to get a flush of growth early
in the spring, and then harden the growth up to prevent late
attacks by the aphid. Eradication of the common weed host
plants will greatly aid in control of the citrus aphid. As is the
case with most insects, much can be done by way of prevention
of infestation by proper cultivation and grove management.









Bulletin 203, Biology and Control of Citrus Aphid 455

Biological Factors.-In referring to the natural enemies of the
citrus aphid, Dr. F. R. Cole (4) states, "The natural enemies of
this citrus aphid are of more than usual interest because so far
as we have observed there are few true parasites. Practically all
control of the aphid by insect enemies during 1924 was accom-
plished by predators. The predators of importance belong to
three orders of insects, Neuroptera, Coleoptera and Diptera. The
usual enemies of aphids are found in Florida and the Coccinellid
beetles are probably of most importance, closely followed by the
syrphid flies, and lacewings being a minor factor in control."
Among the predators that Dr. Cole named were the following:
Trash bugs (Chrysopa sp.) or green lacewings, the ladybeetles-
Olla abdominalis var. sobrina Csy., the twice-stabbed (Chilo-
corus bivulnerus Muls.), the convergent (Hippodamia conver-
gens Guer.), the blood-red (Cycloneda sanguine Linn.) and sev-
eral species of Scymnus, small black ladybeetles. Two species of
syrphus flies, Baccha lugens Loew and Baccha clavata Fab., were
found as well as a species of Agromyzidae, Leucopis americana
Malloch. He also states that the syrphus fly larvae were at-
tacked by a hymenopterous parasite, Pachyneuron siphono-
phorae Ashm.
Professor J. R. Watson and Mr. A. H. Beyer (23) give practi-
cally the same group of predators with a few additional as fol-
lows: Australian ladybeetle (Novius cardinalis) and the hymen-
opterous parasite, Lysiphlebus testaceipes. It is stated that this
parasite is not able to emerge from the citrus aphid. Others
(31) reported the finding by Dr. E. W. Berger of a fungous dis-
ease (probably Empusa fresenii Nowak.). Watson (24) reports
this fungus as effecting a good control during the spring of 1925.
In his bulletin "Citrus Insects and Their Control," Professor
Watson discusses the life history of some of the common preda-
tors as worked out by Mr. W. L. Thompson who also added two
syrphus flies, Syrphus wiedmanni Johnson and Allograpta ob-
liqua Say., to the list.
In a later paper, Dr. F. R. Cole (5) gives a rather complete
list of the predators and also states that the hymenopterous para-
site is quite efficient.
The writer made many observations as to the appearance,
abundance, life history, feeding habits and natural enemies of
the aphid predators and parasites and the results of this work
are shown in the following discussion. The natural enemies of








456 Florida Agricultural Experiment Station

the aphid are quite numerous and are scattered among several
groups of insects.
PREDATORS
ORDER=COLEOPTERA
FAMILY-=COCCINELLIDAE
Cycloneda sanguine Fab.
(Blood-red Ladybeetle)
This small red beetle is the most abundant of all ladybeetle
predators at Lake Alfred. It was found that the masses of yel-
low, cigar-shaped eggs hatch in three to five days. The larvae
eat aphids at
the rate of 16
per day for 10
days or two
weeks, then pu-
pate. The pupal
7. stage lasts from
four to six days.
The adult has
been kept alive
Fig. 114.-Blood-red ladybeetle. Adult, left; pupa, in captivity for
center; larva, right. (From Bul. 183.) over 5 0 days
and eats an average of 65 aphids per day. One can find this
predator during the entire year in the adult stage and in the
larval stage during the entire year except January. The effi-
ciency of this predator is probably greatly impaired by its own
parasites which were found to be quite abundant during the
spring but scarce during the remainder of the year. The para-
sites reared from these larvae are Homalotylus terminalis Say.
and Tetrastichus blepyri Ashmead.

Hippodamia
convergens Guer.
(Convergent
Ladybeetle) p. .

This predace-
ous beetle is not .I
nearly so com-
mon on the cit-
rus aphid as on Fig. 115.-Convergent ladybeetle. Larva, left;
truck crop aphids pupa, center; adult, right. (From Bul. 183.)









Bulletin 203, Biology and Control of Citrus Aphid 457

but is occasionally found in both larval and adult stages. Its life
history was found to be as follows: egg stage, three to five days;
larval stage, 11 to 14 days; pupal stage, six days. The larvae
eat an average of 56 aphids per day and adults eat an average
of 84 aphids per day. No parasites were found but this beetle
is often found dying in great numbers from what seems to be
a bacterial disease.
Coccinella oculata Fab.
or
Olla abdominalis sobrina Csy.
This black beetle with a yellow spot on each wing, is an occa-
sional citrus aphid predator. It lives quite well on the citrus
mealy bug
also. The life
cycle is very
similar to that
of the other
beetles a n d
feeding rec -
ords are sim-
ilar. Eggs
hatch in three Fig. 116. Two-spotted ladybeetle. Larva, left;
to five days, pupa, center; adult, right. (From. Bul. 183.)
larvae mature in two weeks and adults emerge in six days. The
larvae eat an average of 17 aphids per day and the adults an
average of 40. No natural enemies were observed in the field,
but in the lab-
oratory the lar-
vae were very






Scymnus Fig. 117.-Scymnus collaris ladybeetle. Larva, left;
collaris Melsh. pupa, center; adult, right. (From Bul. 183.)
Scymnus terminatus Say.

Scymnus creperus fraternus Lec.
Scymnus brullei Muls.
These small black beetles are quite common but never abund-








458 Florida Agricultural Experiment Station

ant. The larvae of some species are gray while others are cov-
ered with white, waxy tufts which make them resemble mealy
bugs. Tiny pink eggs are deposited singly on infested leaves
and hatch in two to four days. Young larvae pupate in eight
days and emerge in five more. Larvae eat or rather suck out the
juice of an av-
erage of 27
aphids per day
and adults an
average of 30
per day. The
parasite, Anis-
S toylus similis,
subspecies uta-
hensis Timber-
"lake, was reared
from Scymnus
Fig. 118.-Scymnus terminatus. Larva, left; pupa, collaris.
center; adult, right. (From Bul. 183.) Some of the
minor ladybeetle predators of the citrus aphid are the following:
Chilocorus bivulnerus Muls. (Twice-stabbed ladybeetle) ; Rodalia
cardinalis Muls. (Vedalia ladybeetle); Exochomus marginipen-
nis childrenii Muls.; Microweisea coccidivora Ash.; Stethorous
utilis Horn.; Delphastus pusillus Lec.; Zagloda sp. (Near
hystryx); Exochomus latinsculus Csy.; Hyperaspis regalis Csy.;
Hyperaspis binotata Say.
Another ladybeetle imported from China through the Cali-
fornia Experiment Station (Leis sp.) feeds quite ravenously on
the citrus aphid. The Florida Agricultural Experiment Station
has been attempting to establish this beetle in the state but at
the present time it is not possible to state the degree of suc-
cess (28).
FAMILY=TENEBRIONIDAE
Epitragodes tomentosus Lec.
(Downy Darkling Beetle)

This scale-feeding beetle was found to feed also on the citrus
aphid. When caged with aphids, beetles collected from the field
ate eight aphids per day. The life history of this predator was
not studied.








Bulletin 203, Biology and Control of Citrus Aphid 459

ORDER=DIPTERA
FAMILY--SYRPHIDAE
(Syrphus Flies)
Baccha clavata Fab.
The black, slender-bodied, clear-winged adult fly deposits her
elongated white eggs, singly, on leaves and twigs heavily in-
fested with aphids. The eggs hatch in two to four days into
tiny, maggot-like predators which eat an average of 33 aphids
per day until their maturity. The larval stage lasts 11 days and
then pupation takes place on a nearby leaf or twig. The adult
emerges in
four to five
days, making
the complete .
life cycle 17 to
20 days. Adult
flies feed on
pollen of flow-
ers and honey-
dew in the field.
In captivity the
a d u 1 t s w e r e Fig. 119.-Syrphus fly, Baecha clavata. Adult, left;
kept alive for pupa, center; larva, right. (From Bul. 183.)
several days on sugar solutions. The larvae of this insect are
heavily parasitized by Diplazon laetatorius Fab., Syrphophagus
4-maculatae Ashm., Pachyneuron allograptae Ashmead, Pachy-
neuron syrphi Ashm., and a Cynipid. Eggs, larvae and pupae
were killed by a temperature of 260F. during January, 1927, but
according to W.
L. Thompson
most of them
survived the
same tempera-
ture during
January, 1928.

Baccha lugens
Loew.
The adult of
this predator Fig. 120.-Syrphus fly, Baccha lugens. Adult, left;
differs f r o m pupa, center; larva, right. (From Bul. 183.)








460 Florida Agricultural Experiment Station

that of Baccha clavata only in that it has a smoky film on its
wings and abdomen. The eggs are laid singly on aphid infested
twigs and hatch in one to three days. The snail- or slug-like
larvae live six to eight days, eating an average of 35 aphids
per day, then pupate. The adult emerges in 7 to 8 days. Natural
enemies of this predator reared were Diplazon laetatorius Fab.,
Syrphophagus 4-maculatae Ashm., and Pachyneuron syrphi
Ashmead.
Allograpta obliqua Say.
The yellow banded, slender-bodied adult fly with obliquely
marked abdomen is common on citrus aphids during the cooler
season. During the summer none of this species were found on
citrus aphids but were common on truck crop aphids. The elon-
gate, white eggs, laid singly on aphid infested leaves and twigs,
hatch in one to three days. The light green larva with white
markings eats an average of 34 aphids per day and pupates in













Fig. 121.-Allograpta obliqua Say., a predator of the citrus aphid.
Adult, right; pupa, center; larva, left.

10 to 14 days. The adult emerges in six to eight days. Para-
sites of this predator are Diplazon laetatorius Fab. and Pachy-
neuron allograptae Ashmead.

Syrphus wiedemanni Johns.
(Syrphus americanus Wied.)
Another winter predator of the citrus aphid is this common,
yellow banded, plump-bodied fly, Syrphus wiedemanni Johns.
The elongate, white eggs are laid singly on infested twigs and
leaves and hatch in three to four days. The light brown, maggot-









Bulletin 203, Biology and Control of Citrus Aphid 461

like larvae eat an average of 45 aphids per day and pupate in
14 days. The adult emerges in from eight to eleven days. Para-
sites reared from these larvae were Diplazon laetatorius Fab.,
Pachyneuron syrphi Ashm. and Syrphophagus 4-maculatae
Ashm.
FAMILY=-AGROMYZIDAE
Leucopis americana Malloch
This tiny, gray fly, found hovering around aphid colonies, is
there to deposit her minute, white eggs on the infested leaves
and twigs. The eggs hatch in from two to three days into very
small, dirty white maggots with two horns on the posterior end.
These larvae eat an average of 17 aphids per day and pupate in
eight days. Adults emerge in five to eight days more. One hy-
menopterous parasite, a Cynipid, was reared from this predator.

ORDER=NEUROPTERA
(Lacewing Flies)
FAMILY=-CHRYSOPIDAE
(Green Lacewing)
Chrysopa harrisii Fitch.
This delicate, green, lacywinged adult deposits her eggs
singly on a silken thread, spun from the anal gland. The eggs
hatch in three to five days into slender, white larvae with power-
ful jaws. These larvae eat an average of 28 aphids per day for
14 days, then spin a spherical silken cocoon with their anal
glands and there pupate. Ten days later the emerging insect
cuts a round door in the cocoon and crawls out. On the top of
the cocoon the adult emerges, leaving behind the old pupal skin.
This lacewing fly was parasitized by Chrysopoctonus chrysopae
Ashm.
Chrysopa sp. (Near lateralis)
(Trash Bug)
In all respects this predator is similar to the one immediately
preceding except that in the larval stage the young cover them-
selves with dead aphid skins and any other convenient trash.
This trait has won for them the name of "trash bug" and they
certainly resemble an animated trash heap.








462 Florida Agricultural Experiment Station

FAMILY Y=HEMEROBIIDAE
(Brown Lacewing)
Micromus posticus Walker
The brown, slender-bodied lacywinged adult sticks her yellow
eggs, singly and flat, on the leaf. These hatch in two to three
days and the dark red, slender larvae mature in five to seven
days. At pupation a very light, flimsy web is spun in a curled
leaf or crotch of two branches and, suspended in this, the pupal
form remains for seven days. It then crawls out and the adult
emerges. This predator is common only during the summer
months. No parasites were reared from this predator.

ORDER=HEMIPTERA
FAMILY=REDUVIIDAE
Zelus bilobus Say.
FAMILY Y---PHYMATIDAE
Phymata erosa Guer.
These two bugs are found to feed occasionally on the citrus
aphids. They prefer larger prey however, especially flies and
other soft bodied insects, but in some cases they were found to
eat many aphids.

FAMILY=ANTHOCORIDAE (Flower-bugs)
Triphleps insidiosus Say.
Nymphs and young of this small bug can frequently be found
with young aphids on the end of their beaks. They are never
abundant among aphids but are quite common. This insect is
also a common predator of thrips.

PARASITES

ORDER=HYMENOPTERA
FAMILY=BRACONIDAE
Lysiphlebus testaceipes Cres.
This small wasp, which is very beneficial in the control of
other aphids, is somewhat unfortunate in the case of the citrus
aphid. The adults are usually quite common among the aphid
colonies. They proceed to travel over the infested leaves and
puncture the young aphids with their ovipositors. These nymphs
reach maturity and may or may not produce young. In most








Bulletin 203, Biology and Control of Citrus Aphid 463

cases none are produced but occasionally one or two may be
found. Ten days after the aphid is punctured by the wasp
the aphid's body turns yellow, one day later it is a very dark
red and still later it becomes almost black. When these are dis-
sected the dead larva of the parasite can be found inside the old
skin of the aphid. In many trials the writer has never been able
to get an adult parasite to emerge from the citrus aphid, how-
ever Dr. F. R. Cole (5) states that at Orlando, Florida, from 1
to 10 percent of the citrus aphids were attacked by the parasite
and the adult successfully emerged. This difficulty is certainly
very detrimental to the increase of the parasite for the citrus
aphid merely acts as a "trap crop" for the parasite.
Colonies of Aphis gossypii and Toxoptera aurantiae, from
which this parasite can successfully emerge are frequently en-
tirely destroyed in three weeks by this active wasp.

FUNGOUS DISEASES
Three diseases have been reported by Dr. E. M. Gilbert and
W. A. Kuntz (7) as attacking the citrus aphid. They include
an entomophthora, Empusa fresenii Nowak., first reported by

Jan.t Feb.j ilarl Apr.I Mi.a. June. July A.g.1 Sep.1 Oct.I Nov. Dec.
Cycloneda sanguinea I I
Hippodamia convergens '
Coccinella oculata I I



Raccha lugens I I
I I I




Allograpta obliqua -


Chrysopa sp. -- --
Hemerobius sp. --
Lysiphlebus testaceipes -
Empusa fresenii I I
I I I I I I
i I I







Fig. 122.-Occurrence of various aphid predators and parasites during the
year 1926-27 at Lake Alfred, Florida.

Dr. E. W. Berger, entomologist of the Florida State Plant
Board; an olive brown mold, Cladosporium sp., and a white
mold, Cephalosorium sp. Of these three diseases, Empusa
fresenii is by far the most common and most beneficial. Clado-
fresenii is by far the most common and most beneficial. Ckldo-








464 Florida Agricultural Experiment Station

sporium is now considered as a saprophytic organism which
attacks only dead aphids. Cephalosporium is effective on some
truck crop aphids where the plants grow near the ground but
is not efficient in a citrus tree to any appreciable extent.
The fungus, Empusa fresenii, is found wherever aphids are
found and during the entire season. It seems to be more effec-
tive during periods of high humidity and in colonies of aphids
that are old and densely populated.
Summary of Biological Control.-The number of aphids de-
stroyed per day by each predator is given below:
Aphids Destroyed Per Day
Larva Adult Average
Cycloneda sanguine .........-- ......-- ....... 16 65 26
Hippodamia convergens ...................---- 56 84 61
Coccinella oculata ................--... ........ 17 40 21
Scymnus sp. ..----........-- ..-............. ------27 30 20 ?
Baccha clavata .....................--- .....-- 33 ...- 33
Baccha lugens ......................-- ........ 35 .. 35
Allograpta obliqua ......................-..... 34 .. 34
Syrphus wiedemanni ..................-..-..- ... 45 ... 45
Leucopis americana ......---................... 17 ... 17
Chrysopa sp. .................... --...........-. 28 -.... 28
Hemerobius sp. ................-- ...- ........... 20 ... 20
Lysiphlebus testaceipes -...--....-...... actual number found
Empusa fresenii ...--.............. ...... -actual number found

Jan. Feb. Mar. Apr. May. June July Aug. Sep. Oct. Nov. Dec.
100



50

25


Fig. 123.-Percentage of aphids destroyed by all natural enemies.

As can be seen from Fig. 123 the predators and parasites aid
greatly in controlling the aphid when the aphid population is
at a standstill or decreasing but when the aphids are thriving,
the natural enemies are not able to control them.

ARTIFICIAL CONTROL

The first complete report on control work against the green
citrus aphid in Florida was given by Professor J. R. Watson and
Mr. A. H. Beyer (23). This paper reports good success by spot








Bulletin 203, Biology and Control of Citrus Aphid 465

are given for making a good dust of nicotine sulphate and lime.
They also state that infested twigs on young trees can be dipped
successfully in a solution of nicotine sulphate-soap solution with
a good kill as a result. It is suggested that spraying will give
good results if done before the leaves are badly curled but if
delayed will not be successful. In this case a power duster
must be used.
In a later article Professor Watson (28) reports good success
by using a hood attached to the side of a power duster for mak-
ing applications in a light wind. See Fig. 121. In a previous
paper the writer (11) reported success by using snuff as a dust
on wet foliage.
Mr. W. W. Others and Mr. O. C. McBride (33) report that
dusting with a 3 percent nicotine sulphate dust is much more
successful when the conditions are warm (730 F.) and calm
rather than when cool (60 F.) and calm or cool and windy.
In the work carried on by the writer an attempt was made
to use all insecticides and methods available. This work is re-
ported in the following discussion.
METHODS

A great variety of insecticides have been used against the
:green citrus aphid. These insecticides were used at various
strengths and in combination with various spreaders. Not only
were the materials varied greatly but considerable attention was
given to the time and method of application. Spraying with
both hand apparatus and power machinery was used, and dust-
ing by hand and with a power duster was used in the open and
under tents.
Dipping and Spraying.-When a small tree or a few low, ac-
*cessible branches of a large tree are severely infested, the aphids
can be very effectively killed by dipping the infested part into
a mixture of an effective insecticide. When twigs are dipped
they should be thoroughly swished around in the liquid to insure
wetting all aphids. Spraying is quite effective if done thorough-
ly and before the leaves are curled. The spray material must
hit the aphids to kill them, so a high pressure and proper
manipulation of the gun or rod and nozzle are very essential.
Dusting and Fumigation.-Dusting is the most rapid method
of securing a thorough control if a suitable time can be found








466 Florida Agricultural Experiment Station

for the work. Wind enough so that one can tell the direction it
is blowing is too much. To avoid this objection, dusting under
tents, varying in size from 4-foot wire cones, covered with


























OC









Fig. 124.-Dusting apparati and oil damage. A. Power duster with tent
attachment. B. Home-made dust mixer. C. Typical oil damage to ten-
der citrus leaves. D. Typical oil damage to tender citrus twigs.

paraffined cloth, to 40-foot California fumigation tents was
attempted. This method is quite thorough but slow and expen-
sive. A tent-like apparatus was devised and attached to the side









Bulletin 203, Biology and Control of Citrus Aphid 467

of the power duster so that it could be drawn over the row
as it was dusted. This method proved quite satisfactory when
a light wind was blowing. See Fig. 124.
Insecticides Used.-In using the following materials all in-
secticides were used on a small scale for the first few tests. If
some one of the materials appeared to be promising it was used
in the power apparatus on a large scale. The sprays were used
both as dips and in the hand sprayer. The dusts were used in
open dusting and fumigation under tents.
In making observations as to kill of aphids and effect on foli-
age a 24-hour period was always allowed between the time of
application and the time of checking results. The percent of
kill was based on the total number of aphids found dead and
alive after the application. In cases where the aphids dropped
from the twigs when they were killed, counts were made on
marked twigs before the application was made. The strength
of mixtures used is given in percent of the total insecticide or
concentrate in the mixture.

OIL EMULSIONS

In spraying oil emulsions on citrus foliage it is very difficult
to wet the foliage. The emulsion does not usually spread but
gathers in drops. In many cases of burning one can get the
same condition by spraying clear water on the trees during a
period of high temperature and humidity.
Oil emulsions used as insecticides kill most of the aphid preda-
tors. When the plant extracts are used these predators are usu-
ally not injured. Fig. 124 shows typical oil burning on tender
citrus foliage.
PLANT EXTRACTS

DERRIS

This material is not toxic to plants when used at any of the
ordinary spraying strengths. When used against aphids at 1
part to 800 it gave a 99 percent kill and at 1 part to 1,000 it
gave a 95 percent kill. This insecticide however, is a slow act-
ing material and will not kill all the aphids in 24 hours but in
36 to 48 hours it shows its real effectiveness. The writer was
not able to find that derris extracts had any more lasting effect
or repellant action than did nicotine sulphate.








468 Florida Agricultural Experiment Station

NICOTINE SULPHATE

Another plant extract known as nicotine sulphate is one of
the oldest and best aphicides. This material is dark brown,
almost black, in color and flows like syrup. It contains 40 per-
cent nicotine sulphate and 60 percent inert matter. It must be
mixed with soapy water, 1/2 to 1 percent, to get an effective kill-
ing liquid. This mixture is chocolate brown in color and has a
very penetrating odor.
Nicotine sulphate does not injure foliage at any spraying
dilution. When used against the citrus aphid at the strength of
1 to 800 in a 1/2 to 1 percent soap solution it gave a 99 percent
kill. More soap is occasionally necessary if the water is ex-
tremely hard.
One very distinct advantage of this material is the fact that
it makes a very effective dust. When the liquid is poured into
lime and the whole mass agitated for several minutes a very
effective dust results. Seven and a half pounds of nicotine sul-
phate are necessary per 100 pounds of lime for a 3 percent dust.
A home made mixer as shown in Fig. 124 is very satisfactory.
An especially fine dust was made by using lime and sulphur in
equal parts for the carrier. This dust stuck to the foliage better
than when lime alone was used and was more effective when
used against the citrus rust mite.
Nicotine sulphate dusts at 1 percent gave a 37.8 percent kill,
at 2 percent a 99 percent kill and at 3 percent a 99.8 percent
kill of the citrus aphid.

PYRETHRUM

The liquid extract of the flowers of pyrethrum was used
against the citrus aphid with good result. This asphalt like
sample was first dissolved in alcohol and aliquot parts taken.
These were mixed with soapy water and formed a chocolate col-
ored mixture.
This material was not toxic to plants in any ordinary spray
dilution. When used against the citrus aphid at 1 part to 800
of water containing 1 percent soap a 90 percent kill was accom-
plished. With water containing 2 percent soap a 98 percent kill
was accomplished.








Bulletin 203, Biology and Control of Citrus Aphid 469

MISCELLANEOUS INSECTICIDES
LIME-SULPHUR
This common insecticide and fungicide was used at various
strengths. It burned tender foliage when used at stronger dilu-
tions than 1 to 60. When sprayed on the citrus aphid it dried
on the backs of the insects without doing them any harm.
Aphids that had been thoroughly washed or almost drowned in
the solution were killed. After three days an examination
showed a few dead aphids but this number was not important.
SNUFF
Three grades of finely ground tobacco stems, or snuff, were
used both as a dust and in suspensions. These materials are
made from waste tobacco products and the grade depends on the
degree of fineness of the particles. This material contains 2
percent nicotine.
None of these materials damaged the tender citrus foliage.
When dusted on dry citrus aphids at full strength no kill was ac-
complished but if used when the aphids were wet with dew a 95
percent kill resulted. Snuff was mixed with water at the rate
of 15 pounds for 50 gallons and used as a dip and in a hand
sprayer. This mixture gave a 90 percent kill but could not be
used in a power machine.
Snuff mixed with anhydrous calcium chloride was used with
good results as to kill but the calcium chloride damaged the foli-
age. This material was also quite destructive to the duster in
which it was used. Snuff and sulphur mixed in equal parts was
not effective as an aphicide.
FISH OIL SOAP
The dark brown color and fish odor of this material will serve
to identify it anywhere. It was found to contain 50 percent
moisture. When mixed with water it formed a muddy mixture
of suds. When used above 3 percent this soap caused the very
tender twigs to be burned and to drop off but below that dilu-
tion no injury resulted. When used at 1/ percent a 17 percent
kill was obtained, at 1 percent a 71 percent kill resulted, and
at 2 percent a 93 percent kill resulted.
The greatest use for this material is not as an insecticide it-
self but as a spreader for other materials. When used with oils
or plant extracts, as stated before, it increases their efficiency
many times.









SUMMARY OF INSECTICIDAL WORK

Material Percent Emulsion Effect on Tender Citrus Percent Citrus
Aphids Killed
Aldehol S.-
Alone .. ................. .......... ........ 3 No injury .......................--.......-.... 97
With F. O. Soap %% ................... 1 No injury ................................ 96

Oil Emulsion No. 1 (75% oil)................ 1 No damage ............... ................ 63.4
2 Leaves curled and dwarfed .............. 93.7
Oil Emulsion No. 2 (65% oil) ........... 1 No damage ........... ................... Less than 50
2 At high temp. brown spots where
drops stood ................................. .. Less than 50
Oil Emulsion No. 3 (65% oil).............. 1 No damage ................... ..... Less than 50
2 No damage .......... .......... 72.7
3 Few tips slightly burned .............. 84.1
Pine Oil G1 (48% oil)............................ 2 No damage .----................ ........ Less than 50.
3% Y No damage ................................... 98
Pine Oil G2 (48% oil)............................ 2 No damage .......-- -........ ........... ... Less than 50
3% No damage ........... ............... 99
Pine Oil G4 (63% oil)........ ................ 2 No damage ......... ............. Less than 50
3% No damage ...................... 96 Q
Pine Oil G5 ................................... 2 No damage ............ ......... ........... 37
3% No damage ............................ 99
Pine Oil No. 8 (42% oil)..... ........... 2 No damage ........ ......... ...... ........ 25
3% No damage .................... ... .........I 75







SUMMARY OF INSECTICIDAL WORK-Continued

Material Percent Emulsion Effect on Tender Citrus Percent Citrus
Aphids Killed

Renol ......... .......... .............. ......... 1 N o dam age .......................................... 5
2 No damage ................................. 86
3 No damage .................................. 91
Oil Emulsion No. 4 (65% oil)............. 1 No damage ................... .................. Less than 50
2 No damage ................................ Less than 50
Oil Emulsion No. 5 (65% oil).............. 1 No damage ................................... Less than 50
2 No damage ................................... Less than 50
Shale Oil (58% oil) .............................. 1 No damage ................ ....... Less than 50
2 No damage .................................1 65
3 No damage ...................................... 85.8
Oil Emulsion No. 6 (85% oil).............. 1 No damage ........................................ 95
2 Occasional leaf spotted .................. 96
3 Occasional leaf spotted .................. 98
Derris compound .... .............................. 1-800 No damage .......... ................... 99
1-1,000 No damage ...................................... 95
Nicotine Sulphate-
%% F. O. Soap ...................................... 1-800 No damage ......................... 99
Nicotine Sulphate Dust ........................ 1 No damage ......................... ......... 37.8
No damage .................................. ....... 99
No damage ........................................ 99.8
Pyrethrum and-
F. O. Soap 1% .................................. 1-800 No damage ........................ .. ...... 90
F. O. Soap 2% ................................ 1-800 No dam age .......................... ............... 98
_______________ _____ _____________________________I___________










SUMMARY OF INSECTICIDAL WORK-Continued

Percent Citrus
Material Percent Emulsion Effect on Tender Citrus Aphids Killed

Calcium Cyanide No. 1--
Open ............................. .......... 100 Occasional severe damage ............. Less than 50
In Tents ....................... .......... 100 Occasional severe damage ................ 99
Calcium Fluosilicate ..-........ .......100 No damage .............................. None
Calcium Cyanide No. 2 plus 15% sul-
phur ............................................. 100 Occasional severe damage ............. 50
In tents ........ ......... ....... ............ 100 Occasional severe damage ......... 99

Cocotine alone ........ .......... ............ 3p.-100g. No damage .......................... .......... 5
6p.-100g. 'Severe injury ................ ........ I 50
In %% F. O. Soap ... ............... 3p.-100g. No damage ......... ....... ............ 90
6p.-100g. Severe injury ......... ..........-.....-. .... I 98
Lime Sulphur 32 Baume ................ 1-40 Many leaves burned .............--- I None
1-60 No damage ................................. None
Naphthalene ................. ................. 100 No damage ....--........... ....... None

Snuff--
Dry foliage ............... .............. 100 No damage ........ ........ None
Wet foliage .---.......................... 100 No damage ........................... 95
Suspension ....................... 15 lbs. to 50 gal. No damage .-.............................. 90
Fish Oil Soap .....- -................-- ... % No damage ............ ..-- ......... 17
1 No damage ...................................... 71
2 No damage ...... .................--- 91








Bulletin 203, Biology and Control of Citrus Aphid 473

SUMMARY
A new aphid of citrus, Aphis spiraecola Patch, has occurred in
Florida during the last few years and has been quite destructive.
This aphid was known to attack spiraea in the northern United
States but was not found in Florida until 1923.
In Florida this aphid can live on a great number of host
plants but thrives only on tender growth on citrus, spiraea and
apple. Other plants however serve as "overflow" hosts and aid
in carrying the aphid over between flushes of tender growth on
citrus. All varieties of citrus are attacked but those that grow
most slowly and continuously are most severely damaged. At-
tacked trees become dwarfed, the leaves are curled, the amount
of fruit set is small and in general the tree is in a poor state of
growth.
The green citrus aphid reproduces asexually during the entire
year at Lake Alfred while eggs are deposited in the northern
part of the state. The average length of life for the year Aug-
ust, 1926 to August, 1927 was 16.7 days for 198 females. The
longest life recorded was 49 days during December and January.
The nymphal period ranged from 4 to 16 days, being longest dur-
ing the winter and shortest in September. The average nymphal
period was 6.93 days for 198 females. The rate of reproduction
was greatest at a temperature of 75 to 80 degrees and averaged
29.11 for 198 females. The maximum number produced per day
by one female was 16.
Aphids fed in crowded conditions or on hardening foliage pro-
duce many winged forms while if fed on tender growth separate-
ly, no winged forms appear. The citrus aphid reacted very little
to gravity, concentrated under the shade produced by cheese-
cloth, concentrated at the temperature 72 to 93' F. and in cap-
tivity were slightly attracted to their preferred host plants.
Aphids lived twice as long when subjected to 100 percent humid-
ity as when humidity was low. A large number of insects were
found feeding on the honeydew secreted by the citrus aphid.
A great number of natural agencies tend to control the citrus
aphid but none of these are efficient enough to make artificial
control unnecessary. Rain, wind and changes of temperature
are all destructive under some conditions. Many species of lady-
beetles and syrphus fly predators as well as lacewing flies and
others were observed but none of these were able to do more
than partially check the aphid increase. One hymenopterous
parasite attacks the citrus aphid but is not generally able to








474 Florida Agricultural Experiment Station

emerge successfully from the aphid's body. A fungous disease
is ever present but during 1926-27 was of little value as a con-
trol.
This pest can be successfully controlled by either spraying or
dusting if done thoroughly and in good time. In general, oils
were not satisfactory aphicides but some seem quite promising.
Extracts of derris and nicotine sulphate were most successful
and gave the most consistent control.

BIBLIOGRAPHY

1. Beyer, A. H.-A New Aphid on Citrus
Fla. Ento. 1924. VII No. 4, pp. 58-59.
2. Beyer, A. H.-Life History of the New Citrus Aphid.
Fla. Ento. 1924. VIII No. 1, pp. 8-13.
3. Bragdon, K. E.-Some Field Observations on the New Citrus Aphid.
Citrus Industry (5) 1924. No. 9, pp. 9, 24.
4. Cole, F. R.-Natural Enemies of the Citrus Aphid (Aphis Spiraecola
Patch).
Journal of Econ. Ento. Vol. 18. No. I, 1925. pp. 219-223.
5. Cole, F. R.-New Facts About the Citrus Aphid and its Natural Ene-
mies.
Proc. Fla. Hort. Soc. 1926. pp. 156-168.
6. Davis, J. J.-A List of Aphididae of Illinois with Notes on Some of
the Species.
Jour. Econ. Ento. 1910. Vol. 3. p. 490.

7. Gilbert, E. M. and Kuntz, W. A.-Some Diseases of Aphis spiraecola
Patch.
Fla. State Plant Board Quar. Bul. X 1926. pp. 1-6.
8. Gillette, C. P.-Plant Louse Notes.
Jour. Econ. Ento. 1910. Vol. 3, p. 404.
9. Heimburger-The New Citrus Aphid.
Fla. Grower. 29: 17, 13. 1924.
10. Kelly, R. W.-The New Aphis Controlled by Gas.
Citrus Industry (5) 1924. No. 6. pp. 8, 9, 32. Fig. 3.
11. Miller, R. L.-Snuff as an Insecticide.
Proc. Fla. Hort. Soc. 1926. pp. 165-167.
12. Miller, R. L. and Thompson, W. L.-Life Histories of Ladybeetle
Predators of the Citrus Aphid.
Fla. Ento. Vol. XI. No. I. pp. 1-8. 1926.
13. Patch, E. M.-Maine Aphids of the Rose Family.
Maine Bul. 233. p. 270. 1914.
14. Patch, E. M.-The Summer Food Plants of the Green Apple Aphid.
Maine Bul. 313, 1923. pp. 45-60.









Bulletin 203, Biology and Control of Citrus Aphid 475

15. Pierstorff, A. L.-Control of Aphids on Nursery Stock.
Jour. Econ. Ento. Vol. 18. 1925. I. pp. 227-230.
16. Schouteden, H.-Aphidologische Notizen.
Zoologischer Anzeiger. Vol. 25, 1902. pp. 656-657.

17. Thompson, W. L.-Life Histories of Ladybeetle Predators of the Cit-
rus Aphid.
Fla. Ento. Vol. X. No. 3. Vol. X No. 4. pp. 57-59 1926.
18. Tissot, A. N.-Some Observations on the Life History of the Citrus
Aphid (Aphis spiraecola Patch).
Fla. Ento. 1926 X. No. 2. pp. 26-27.
19. Tissot, A. N.-The Identity of the New Citrus Aphid.
Fla. Ento. 1926 X. No. 4. pp. 56-57.
20. Watson, J. R.-The New Citrus Aphid.
Fla. Agr. Experiment Station, Press Bul. 358. May 10, 1924.

21. Watson, J. R. and Beyer, A. H.-The New Citrus Aphid.
Citrus Industry (5) 1924. No. II. pp. 30-31. Fig. 1.

22. Watson, J. R.-The Aphid Situation.
Fla. Ento. 8. 24. 1924.
23. Watson, J. R. and Beyer, A. H.-Controlling the Citrus Aphid.
Fla. Agr. Exp. Sta. Bul. 174. 1925. pp. 81-96.
24. Watson, J. R. Another Year of the Citrus Aphid.
Fla. Ento. Vol. IX. No. I. 1925. pp. 9-13. No. 2. pp. 26-28.
25. Watson, J. R.-Stamping Out the Citrus Aphid During the Winter.
Fla. Press Bul. 375. 1926.
26. Watson, J. R.-The Citrus Aphid in Cuba.
Fla. Ento. Vol. IX. p. 57.
27. Watson, J. R.-Decrease of the Citrus Aphid During the Summer.
Fla. Ento. Vol. X. No. 2. 25. 1926.
28. Watson, J. R.-Another Year's Experience with the Citrus Aphid.
Proc. Fla. Hort. Soc. 1926. pp. 159-164.
29. Watson, J. R.-Citrus Insects and Their Control.
Fla. Agr. Exp. Sta. Bul. 183. 1926. pp. 361-373.
30. Watson, J. R.-Status of the Green Citrus Aphid.
Proc. Fla. Hort. Soc. 1927.
31. Others, W. W.-Florida Grower. Sept. 20, 1924.
32. Others, W. W. and Cole, F. R.-The Citrus Aphid (Aphis spiraecola
Patch).
Citrus Industry (5) 1924. No. 10. pp. 6-8, 18-19.
33. Others, W. W. and McBride, O. C.-Factors Affecting the Control of
the Green Citrus Aphid with Nicotine Dust.
Proc. Fla. Hort. Soc. 1926. pp. 169-171.









476 Florida Agricultural Experiment Station




CONTENTS
PAGE
INTRODUCTION ......---........ ... ............ .....-.... ............- ..... .......-..... .. 431
IDENTITY OF THE APHID ..---...--....-------.... -------....----.......- -...--...........-..... 431
HISTORY AND DISTRIBUTION.................. ....................................... 433
HOST PLANTS .......................... ..-.... ....... ......... .......-... .. .. ............ 433
Varieties of citrus attacked ............................ .................... 439
DAMAGE CAUSED BY THE CITRUS APHID .......- ............................ .... 441
LIFE HISTORY ........................................................................ ..442
OCCURRENCE OF WINGED FORMS.......-...............--- .................. 447
REACTIONS OF THE CITRUS APHID.........................-........................... 449
Geotropism ...............-......... .. .....................-...- ....... 449
Phototropism ................. ..........................---...... -. 449
Thermotropism ......--........-......................... ................... 450
Chemotropism -.... ............ ............................... 451
Thigmatropism -.............................. ........................ 451
Effect of humidity -........................................... ....... ........ 451
INSECTS FEEDING ON HONEYDEW ...................... ............................ ..- 453
NATURAL AGENCIES TENDING TO CONTROL THE CITRUS APHID ----.............. 454
Meteorological Factors .................................. ............. 454
Cultural Factors ...................................... ......................... ... 454
Biological Factors .......................... .. .................... 455
Predators ............ .. .. . ................. .................. 456
Cycloneda sanguine Fab............. ............ .............-....... 456
Hippodamia convergens Guer. ................. .........-............ ......... 456
Coccinella oculata Fab. ........-.. ---........... ..................-...... 457
Olla abdominalis sobrina Csy ................................. ............... 457
Soymnus collaris Melsh ......... .... ................................... ... 457
Soymnus terminatus Say. ....................- ............. .......... 457
Seymnus creperus fraternus Lec. ......... .......-... ..................... 457
Soymnus brullei Muls. ............ ......... .... .................... 457
Epitragodes tomentosa Lee. ................ .. ..... .....--.........- 458
Baccha clavata Fab. .............. ..............................-.. 459
Baccha lugens Loew ....... ....... .......... .......... ............... 459
Allograpta obliqua Say. ..............----..................... .....-.. ........ 460
Syrphus wiedemanni Johns. ................-.... ........................... 460
Leucopis americana Malloch ...........................................-.... ... 461
Chrysopa harrisii Fitch ..........-.....- ............ ........... ....-.... 461
Chrysopa sp. ...................................... ................... ......- 461
Micromus posticus Walker ...........................................- ........ 462
Zelus bilobus Say. ....................... ............................ ... 462
Phymata erosa Guer. ...... .......................................... ..... 462
Triphleps insidious Say ...... --..................... ........ 462
Parasites ........................... ..................... 462
Lysiphlebus testaceipes Cres ............... -- ...............- ................ 462
Fungous Diseases ............................--- ................ ...... ..... 463
Summary of Biological Control ................................-- ........ 464
ARTIFICIAL CONTROL .............................-.....-......... - .......... 464
Methods .-..-......---------.. -................ ..... .. . .............. 465
Insecticides Used ....-....... .... -............ ...... ...... 467
Oils --...........-----....--.....---- ......... ---.... .........-..... 467
Plant Extracts -..................................... ...... 467
Miscellaneous Insecticides --............................ .... 469
Summary of Insecticidal Work ..-..............-- ........ .... 470
SUMMARY .............- -------.....-.. .. ........ 473
BIBLIOGRAPHY ....... .... ............... ......474





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