• TABLE OF CONTENTS
HIDE
 Front Cover
 Credits
 Important facts
 Table of Contents
 Introduction
 Means of control
 Fungus parasites of whitefly
 How fungi propagate
 Methods for intorducing whitefly...
 Conditions favorable for the...
 When to introduce fungi
 Success in introducing the...
 Efficiency of the fungi
 Plan of campaign
 Where fungi may be bought
 The fungi
 Artificial means of control
 Quarantine
 Food plants of the whitefly
 Plants to be condemned
 Whitefly living on fallen...
 Results of defoliation
 Honeydew
 Life history of whitefly
 Two species of citrus whitefly
 Reference














Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 97
Title: Whitefly studies in 1908
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 Material Information
Title: Whitefly studies in 1908
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 97
Physical Description: Book
Language: English
Creator: Berger, E. W.
Publisher: University of Florida Florida Agricultural Experiment Station
Publication Date: 1909
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Table of Contents
    Front Cover
        Page 39
    Credits
        Page 40
    Important facts
        Page 41
    Table of Contents
        Page 42
    Introduction
        Page 43
    Means of control
        Page 43
    Fungus parasites of whitefly
        Page 43
    How fungi propagate
        Page 44
    Methods for intorducing whitefly fungi
        Page 45
        Page 46
    Conditions favorable for the fungi
        Page 47
    When to introduce fungi
        Page 48
    Success in introducing the fungi
        Page 49
    Efficiency of the fungi
        Page 50
    Plan of campaign
        Page 50
    Where fungi may be bought
        Page 51
    The fungi
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
    Artificial means of control
        Page 58
    Quarantine
        Page 59
    Food plants of the whitefly
        Page 60
    Plants to be condemned
        Page 61
    Whitefly living on fallen leaves
        Page 62
    Results of defoliation
        Page 63
    Honeydew
        Page 63
    Life history of whitefly
        Page 64
        Page 65
        Page 66
    Two species of citrus whitefly
        Page 67
        Page 68
        Page 69
    Reference
        Page 70
        Page 71
Full Text



FEBRUARY, 1909.


Florida

Agricultural Experiment Station.





WHITEFLY STUDIES

IN 1908.

BY
E. W. BERGER, Ph.D.


Fig. 1. Eggs and Adults of Aicyrol.ex cifri.
x 2. From Bulletin 67.


The Bulletins of this Station will be sent free to any address in Florida upon
application to the Director of the Experiment Station, Gainesville, Fla.
The Record Co., St. Augustine, Fla.


BULLETIN No. 97.
















BOARD OF CONTROL.


N. P. Bi, lN, Chairman, Jacksonville, Fla.
P. K. YoNC.:, Pensacola, Fla.
T. B. KINc, Arcadia, Fla.
J. C. B.\irnF;N, Live Oak, Fla.
1F. L .\iRTMXN.N, Citra, Fla.



STATION STAFF.

P. H. RoLes, M. S., Director.
A. W\\. I.LAIR, A. M., Chemist.
JOHN MA. ScoTT, B. S., Animal Industrialist.
E. \\. BERGER, PH. D., Entomologist.
H. S. FawCT`.TT, M. S., Plant Pathologist.
IB. F. FLoYD, A. M., Assistant Plant Physiologist.
R. Y. \WINTE)RS, B. S., Assistant in Botany.
*R. N. \VILsON, A. B., Assistant Chemist.
JOHN BELLING, B. SC., Assistant in Horticulture.
MRs. E. W. BERGxcE, Librarian.
K. II. GRAH,\Mi, Auditor and Bookkeeper.
J T.BLRKmNRD, JR., Stenographer.
M. CREws, Farm Foreman.
ALIRI :1) DiCKINSON, Gardener.


'Temporary Assistant.





















IMPORTANT FACTS.
1. It is easy. in Florida, to infect the whiterti larvae with the
parasitic fungi by spraying on the spores at the proper time.
2. The proper time to spray with fungus spores is when there
are many young larve ,on the leaves and the weather is both moist
and warm.
3. The fungi should be put on the trees as early in the season
as possible, in order that their growth may Le helped by the summer
rains.
4. If the fungi are applied late in the >eason, they will probably
not increase sufficiently until the next year.
3. During the winter it is sometimes advisable to spray badly
infested trees with contact insecticides.
G. It is much cheaper to keep the ..1 Ini. out of a community
or out of a grove, if possible, than to control it after it has once
entered.
The Experiment Station has no funds available for distribut-
ing the whitetv fungi. These fungi can i1: obtained. however, from
1p ivate individuals.











CONTENTS.
Page.
Introduction ............................................. 43
M eans of Control.......................................... 43
Fungus Parasites of Whitefly ............................... 43
How Fungi Propagate ..................................... 44
Methods for Introducing Whitefly Fungi ..................... 45
Spore-spraying Method ................................ 45
Leaf-pinning Method .................................. 46
Tree-planting Method......................................... 47
Conditions Favorable for the Fungi .......................... 47
When to Introduce Fungi................... ....................... 48
Success in Introducing the Fungi ............................ 49
Efficiency of the Fungi .................................... 50
Plan of Campaign. ......................................... 50
Where Fungi can be Obtained. .............................. 51
The Fungi .... .............. ............. ........... 51
Red Fungus of Whitefly................. ................. .. 51
Yellow Fungus of Whitefly. ........................... .. 5
Brown Fungus of Whitefly ........................... 53
White-fringe Fungus of Whitefly.................. ..... 54
Cinnamon Fungus of Whitefly ...... .............. 55
Sporotrichum Fungus of Whitefly. ....................... 56G
Fungus Super-Parasites ............................... 56
Sooty M old ....................................... 5
Artificial Means of Control ................................. 58
Q quarantine ............................................... 59
Food Plants of Whitefly................................ ....... 60
Plants to be Condemned... ...... .. .............. 61
Whitefly Living on Fallen Leaves. .......................... 62
Results of Defoliation ..................................... 63
H oneydew ............ ...................... ........ ... 63
Life-history of Whitefly. ..................... ............. 64
Two Species of Citrus Whitefly in Florida ................... 6'
R eferences .................................... ........ 70







WHITEFLY STUDIES IN 1908.
BY E. WV. BERGER, Ph. I).

INTRODUCTION.
The present bulletin includes a revision of Bulletin 88, issued in
January. 190,.1 and also a report of progress.
During 1908 the whitefly has continued to spread to citrus-grow-
ing sections of the State which had not hitherto been infested.
Vehicles, railroad trains, and infested nursery stock are perhaps the
chief means by which it is spreading to all those parts of the State
where citrus fruit is grown, or where its other food plants are found.
WVhile a few citrus-growers still treat the spread of the whitetly as
insignificant, and believe that it will disappear of its own accord, this
number does not include the owners and managers of the larger prop-
erties. These are greatly interested in and ready to adopt such means
as promise relief.
MEANS OF CONTROL.
The means of control are first, natural enemies; and second,
artificial methods.
Among the natural enemies of insects are fungi. bacteria, and
predaceous insects. I acterial diseases of the whitefly are at present
unknown, but the known fungus diseases of this insect are seven in
number. Several predaceous insects are also known to feed on the
larvae of the whitefly.
The artificial means for controlling insects include contact in-
secticides, stomach poisons, and fumigation with a poisonous gas.
The whitefly can not be killed by stomach poisons, such as compounds
of arsenic, since it is a sucking insect and draws its food from the
interior of leaves by means of a beak. Spraying solutions which kill
the insect by contact, and fumigation, are therefore the artificial
methods for combating this pest.
FUNGUS PARASITES OF WHITEFLY.
Fungi are among the lowest plants known. They are devoid of
the green coloring matter which is characteristic of higher plants.
Mushrooms, toadstools, mildews and molds are familiar examples.
As regards their methods of feeding, fungi may be either para-
sites or saprophytes. Fungus parasites infect and often destroy living
plants or animals. The withertip fungus of citrus trees and the rust
of tomatoes are familiar examples of fungi which live on plants. The
seven fungus parasites of the whitefly, also the red-headed scale
fungus, the white-headed scale fungus, and the black scale fungus,
are examples of fungi infecting insects. Saprophytic. fungi are those
that grow only on dead organic matter. These include most of the
fungi growing on rotten wood, or on the ground in fields or forests.
Toadstools. mushrooms, and the molds of bread are familiar examples.







WHITEFLY STUDIES IN 1908.
BY E. WV. BERGER, Ph. I).

INTRODUCTION.
The present bulletin includes a revision of Bulletin 88, issued in
January. 190,.1 and also a report of progress.
During 1908 the whitefly has continued to spread to citrus-grow-
ing sections of the State which had not hitherto been infested.
Vehicles, railroad trains, and infested nursery stock are perhaps the
chief means by which it is spreading to all those parts of the State
where citrus fruit is grown, or where its other food plants are found.
WVhile a few citrus-growers still treat the spread of the whitetly as
insignificant, and believe that it will disappear of its own accord, this
number does not include the owners and managers of the larger prop-
erties. These are greatly interested in and ready to adopt such means
as promise relief.
MEANS OF CONTROL.
The means of control are first, natural enemies; and second,
artificial methods.
Among the natural enemies of insects are fungi. bacteria, and
predaceous insects. I acterial diseases of the whitefly are at present
unknown, but the known fungus diseases of this insect are seven in
number. Several predaceous insects are also known to feed on the
larvae of the whitefly.
The artificial means for controlling insects include contact in-
secticides, stomach poisons, and fumigation with a poisonous gas.
The whitefly can not be killed by stomach poisons, such as compounds
of arsenic, since it is a sucking insect and draws its food from the
interior of leaves by means of a beak. Spraying solutions which kill
the insect by contact, and fumigation, are therefore the artificial
methods for combating this pest.
FUNGUS PARASITES OF WHITEFLY.
Fungi are among the lowest plants known. They are devoid of
the green coloring matter which is characteristic of higher plants.
Mushrooms, toadstools, mildews and molds are familiar examples.
As regards their methods of feeding, fungi may be either para-
sites or saprophytes. Fungus parasites infect and often destroy living
plants or animals. The withertip fungus of citrus trees and the rust
of tomatoes are familiar examples of fungi which live on plants. The
seven fungus parasites of the whitefly, also the red-headed scale
fungus, the white-headed scale fungus, and the black scale fungus,
are examples of fungi infecting insects. Saprophytic. fungi are those
that grow only on dead organic matter. These include most of the
fungi growing on rotten wood, or on the ground in fields or forests.
Toadstools. mushrooms, and the molds of bread are familiar examples.







WHITEFLY STUDIES IN 1908.
BY E. WV. BERGER, Ph. I).

INTRODUCTION.
The present bulletin includes a revision of Bulletin 88, issued in
January. 190,.1 and also a report of progress.
During 1908 the whitefly has continued to spread to citrus-grow-
ing sections of the State which had not hitherto been infested.
Vehicles, railroad trains, and infested nursery stock are perhaps the
chief means by which it is spreading to all those parts of the State
where citrus fruit is grown, or where its other food plants are found.
WVhile a few citrus-growers still treat the spread of the whitetly as
insignificant, and believe that it will disappear of its own accord, this
number does not include the owners and managers of the larger prop-
erties. These are greatly interested in and ready to adopt such means
as promise relief.
MEANS OF CONTROL.
The means of control are first, natural enemies; and second,
artificial methods.
Among the natural enemies of insects are fungi. bacteria, and
predaceous insects. I acterial diseases of the whitefly are at present
unknown, but the known fungus diseases of this insect are seven in
number. Several predaceous insects are also known to feed on the
larvae of the whitefly.
The artificial means for controlling insects include contact in-
secticides, stomach poisons, and fumigation with a poisonous gas.
The whitefly can not be killed by stomach poisons, such as compounds
of arsenic, since it is a sucking insect and draws its food from the
interior of leaves by means of a beak. Spraying solutions which kill
the insect by contact, and fumigation, are therefore the artificial
methods for combating this pest.
FUNGUS PARASITES OF WHITEFLY.
Fungi are among the lowest plants known. They are devoid of
the green coloring matter which is characteristic of higher plants.
Mushrooms, toadstools, mildews and molds are familiar examples.
As regards their methods of feeding, fungi may be either para-
sites or saprophytes. Fungus parasites infect and often destroy living
plants or animals. The withertip fungus of citrus trees and the rust
of tomatoes are familiar examples of fungi which live on plants. The
seven fungus parasites of the whitefly, also the red-headed scale
fungus, the white-headed scale fungus, and the black scale fungus,
are examples of fungi infecting insects. Saprophytic. fungi are those
that grow only on dead organic matter. These include most of the
fungi growing on rotten wood, or on the ground in fields or forests.
Toadstools. mushrooms, and the molds of bread are familiar examples.







Florida Agricultural Experiment Station


The fungus body produced on a whitefly larva is spoken of as a
fungus pustule. Such a pustule is limited in its growth by the amount
of food furnished by a single larva, so that the pustules can not in-
crease beyond a certain size. Their size varies with the size of the
larva attacked. The largest pustules are about three-sixteenths of an
inch in diameter, while the smallest are smaller than a pin's head.
Six fungus parasites are at present known to infect the larvae of
the whitefly, and a seventh infects both larvae and adults. The follow-
ing table gives the common and scientific names of these fungi, with
the dates of their discovery on the whitefly in Florida:
1. Red fungus of lii.. ii. (Aschcrsonia alcy rodis Webber) 1893
2. Brown fungus of 1i. 0i .......... ..... ....... 1896.
.3. Red-headed scale fungus (SphIaerostilbe coccophila Tul.) 1903.
4. Yellow fungus of whitefly (Aschersonia flavo-citrina
P. Henn. ) ................................. 1906.
5. White-fringe fungus of Ii. 1I (M icroccra sp.) ..... 1907.
6. Cinnamon fungus of ii._.II (T'rticilliumn hetero-
cladiun Penzig) .............................. 1907.
7. Sporotrichtmi sp., similar to the chinch bug fungus
(S. globiliferum), infects the adult whitefly and
some of the larv ........................... 1908.
The first six fungi, when present, are found on the under surfaces
of whitefly-infested citrus leaves, and kill the larvae, transforming them
into pustules which have the color and appearance characteristic of
the particular fungus. The red-headed scale fungus is only occasion-
ally found infecting whitefly larve, and will not be further discussed
in this bulletin. So far, no fungus capable of infecting the eggs of
the whitefly has been discovered. XWith regard to these seven fungi,
reference may be made to Bulletin 94, and also to Special Studies,
No. 1, University of Florida.2
HIOW FUNGI PROPAGATE.
Fungi more generally propagate by spores than in any other
way. The spores of fungi are minute microscopic bodies produced
in countless millions, and are mostly used when we desire to start a
new growth of fungus. They take the place of the seeds produced
by the higher plants, but do not have the same structure as seeds.
A single spore is invisible to the unaided eye. The spores of two of
the fungus parasites of the whitefly, the red and the yellow fungi,
.are boat-shaped and pointed at both ends. About 1,700 of them
,could be placed end to end along a line one inch long, and more
than 8,000 could be arranged side by side along the same line.
About 13,600,000 of these spores could thus be arranged upon the
surface of a square inch. Thousands of spores are borne in each
bright red or yellow pustule of these fungi. These spores are washed
out when the Aschersonias are placed in water. Some fungi may







Bulletin 97


also be propagated by portions of the thread-like growths which
make up the mass of the fungus. This method of propagation is
analagous to the propagation of the higher plants by cuttings. A
good illustration of this is the use of "spawn" for propagating the
common mushroom. This spawn consists of dry fragments of the
underground growth of the mushroom embedded in manure or other
vegetable matter. Whether any of the fungus parasites of the white-
fly are propagated in this way has not been demonstrated; but the
peculiar network of threads of the brown fungus which extends over
the citrus leaves, and even over the leaf-stalks, suggests that this
fungus may perhaps be propagated by fragments of these threads
being carried by the wind. by insects, or otherwise, from one leaf to
another.
METHODS FOR INTRODUCING WHITEFLY FUNGI.
There are three methods which have been used for introducing
these fungi into whitefly-infested trees. These are the spore-spraying
method, the leaf-pinning method, and the tree-planting method. These
methods are based mainly upon experiments with the red. yellow,
and brown fungi.
SPORE-SPRAYING METHOD.
This method is the best one of the three. It consists in washing
the spores from fungus pustules by means of water, and then spraying
the mixture of spores and water onto the under surfaces of the
whitefly-infested leaves. (The writer's earlier successful experiments
with this method were made at Lake City in July, and at Leesburg
in August 1900, with the spores of the red Aschersonia.) About
forty of the bright red or yellow pustules of the fungus should be
used to a pint of water. This will be about the same as one or two
fungus-bearing leaves to a quart of water. More fungus may be
used if procurable, but the amount indicated has been found to give
good results. Immerse the fungus-bearing leaves in water, and stir
occasionally during ten or fifteen minutes, then strain the liquid
through cheesecloth or fine wire gauze. While spraying the mixture
of spores and water onto the under surfaces of the whitefly-infested
leaves, look well to the newer growth, e 1.. 11 the water sprouts.
This young growth is generally most infested with the younger
whitefly larvxe, since the winged females always seek out young leaves
when depositing' their eggs. It should be remembered that the
younger larvae are more easily infected with the fungus than the older
larvaI. If the supply of fungus is limited, spray only the worst
infested twigs and branches: for the fungus will infect some of the
larve, and the adults maturing from those not infected, together with
other adults migrating there, will carry the fungus spores to other
parts of the tree and to other trees. It is considered better practice
to spray the infested parts of all trees with a weak mixture, than to







Florida Agricultnral E.rperimicnt Station


spray only a part of the trees in a grove with a strong.mixture. Use
a new spraying outfit, preferably one of the compressed air type (3 or
4 gallons capacity), with no copper or brass about it excepting the
nozzle. The finer the spray, the better; since it is only necessary just
to wet the leaves, and whatever liquid runs off is lost.
On no account should the spraying solution be permitted to
stand in a copper or brass vessel, since an exceedingly small amount
of copper in solution will retard or destroy the germinating power
of the spores. Do not use an outfit which has been previously used
for spraying Bordeaux or other strong fungicide, since a very small
amount of fungicide left in the machine may kill the spores. An old
spraying outfit which has been used only for soap solutions or oil
emulsions, may be employed; but it should be well washed out. A
larger specially made spraying machine mounted on a barrel may be
used when many acres are to be sprayed and when an abundance of
fungus is available.
A simple modification of the spore-spraying method consists in
flirting the liquid against the under surfaces of the leaves by means
of a tin cup. A wisp broom has also been employed, or a bunch of
small twigs dipped into the liquid.
Cost of introducing fungus by this method.-This will vary
with the size of the trees. One correspondent reports that it has
cost him two cents per tree to spray his grove of medium-sized trees.
In another case it is costing one cent per tree to spray; but, in this
instance, the fungus was procured at the slight expense of picking
it from other trees. The writer helped to spray -50 i medium-sized
trees during the last week of September, T!IIS, with spores of the red
fungus, using about one gallon of liquid per tree. About eight
fungus-bearing leaves were used to prepare a gallon of this liquid.
The leaves cost $1 per thousand. This made the total cost per tree.
for fungus and labor, about 5 cents. \An all-iron spray-pump.
mounted on a barrel, was used for spraying this grove. This method
is applicable to all the fungus parasites of the whitefly, when they
are in the spore-bearing stage. The brown fungus does not always
have spores; hence there is more or less uncertainty when one attempts
to introduce it by the spore-spraying method. Some excellent
growths of the brown fungus have, however, been started hi this
method.
L,:AF-P'IN N i NN (; 1iE;'T1 ).
This method is considered second best. In introducing fungus
by this means, the writer has usually pinned from two to a dozen
fungus-covered leaves to the under surfaces of leaves of a whitefly--
infested tree. In Bulletin SS.1 the writer recommended that each leaf
should be pinned w ith its under, or fungus-covered surface, facing
downward. Later observations have confirmed this as the proper
wav to pin the leaves, since the adult whiteflies creel) over the under








Bulletin 97


surfaces of the leaves. and in so doing probably get many of the
spores attached to their feet, and then carry them to other leaves.
For the same reason the'leaves should be pinned to those parts of a
tree where the adult whiteflies are most abundant: that is, on the
newest growth. It might also be well to pin the leaves so that the
drip from them. when it rains, will run onto a cluster or several
clusters of leaves beneath them. At all events, we sometimes find
that fungus starts to develop on the leaves of clusters underneath
the leaves pinned on.
Since the adult whitefly appears to be instrumental in the distri-
bution of fungus (this probably applies mainly to the red and yellow
fungi) we would expect to get the best results with the leaf-pinning
method at those times when adults are most albndant in the trees.
Such is the case: for late in the fall when no adults or only a few
were about, no growth of fungus, or ollyl a very poor growth, resulted
from pinning on the fungus-covered leaves while in most instances
promising growths of fungus resulted from spraying the spores.
Similar observations were made at other times when few adults were
on the wiing and then only a restricted growth of fungus resulted
from pinning on leaves, while a wide-spread growth came as a conse-
quence of spraying the spores. Other crawling and flying insects
are also probably instrumental in distributing fungus spores. (The
leaf-pinning method may he used with all the whitefly fungi.)
TR ;':-'LAXTING AlIETiOD.
Small whitefly-infested trees, having an abundance of a whitefly-
destroying fungus on their leaves, have been temporarily planted by
some of the citrus-growers, so that their foliage came in contact with
that of the-infested trees into which it was desired to introduce the
fungus. When necessary, these trees were planted in pots or tubs,
and elevated on platforms. This method of introducing the fungi,
although useful, is not so advantageous as either the spore-spraying
or the leaf-plinning methods, and is of course, much more expensive.
It requires considerable care in the way of watering to keep the
small tree from dropping its leaves while the fungus is spreading
to the tree ini which it is wanted. Like the leaf-pinning method, this
method is probably dependent mainly upon the adult whiteflv and
other insects for spreading the fungi, especially the red and yellow
fungi, from one tree to another. This method is applicable to all the
fungi of the whitetly.
CONDITIONS FAVORABLE FOR THE FUNGI.
All fungi thrive best in the presence of abundant moisture.
Observations show that the fungus parasites of the whitefly are
most effective in destroying this pest when the atmosphere in a grove
is most humid, as it is during the period of summer rains. On page
53 of Bulletin 88,1 the writer called attention to the desirability of







48 Florida Agricultural Experiment Station

arranging conditions in a citrus grove to promote dampness of the
air about the trees. Plenty of vegetation (trees, shrubs, tall grasses,
etc.) around and in a grove will do this to a great extent. Trees and
shrubs should be arranged as windbreaks. while grasses or beggarweed
should be permitted to grow tall and rank, as a cover crop at the proper
time. Mulching around and between the trees will also help to conserve
moisture. Wherever an irrigating outfit is employed, ti;e trequent wet-
ting of the trees or the soil in dry weather would add to the efficiency of
the fungi. Such a use of the irriga.ing outfit wll11 also reduce "red
spider" and rust-mite, and favor the activities of the snails xhich
feed on the sooty mold.
Warmth is a necessary condition for the rapid .development of
the fungi. This condition is generally realized in Florida from the
beginning of April until October. During this period the fungus
parasites of the whitefly thrive well if the warm weather is accom-
panied by enough rain. Careful observations during the cooler
months, from September or October to March, indicate that the
fungi grow and spread but slowly during this period, notwithstanding
that either rains or heavy dews may supply much moisture.
WHEN TO INTRODUCE FUNG1.
The period of summer rains, which often lasts from June to
September, is generally the lest time in which to bring the fungi into
a grove; but the stage of development of the whitefly larvae is also
important. Experiments with the red and yellow fungi, by the spore-
spraying method, on January 17 and March 17, 1908, in trees in
which the whitefly had advanced to the fourth larval or to the pupal
stage, did not result in any growth of fungus. Similar experiments
made on October 3. 1!906(, and November 29, 1907, with the same
fungi and the spore-spraying method, resulted in some growth of
fungus, notwithstanding that the conditions of moisture and temper-
ature were no more favorable for fungus growth during these months
than during January or March. But young larvae are present in
considerable numbers until December and sometimes later, and these
are apparently more easily infected than are the older larvae or the
pupie. This may account for the failure to get a growth of fungus in
January or March, when young larvre are very scarce or absent. No
experiments have been made during December and February; but
these two months resemble January and March so closely both in
regard to climate and the condition of the i,; I' larvae, that probably
little or no success would be obtained. Experiments with the same
fungus by the same method at Detand on April 21 and 22, 1908. in
trees in which the i. 0l was mainly in the first and second larval
stages, just after the disappearance of the spring brood of adults,
resulted in a heavy growth of fungus, and by the 17th of the following
June a third to a half of the I,1tli larve had become infected and
were dead. Showers of rain immediately followed or preceded some







Bulletin 9 49

of these spore-sprayings, and were probably factors in bringing about
the result.
To sum up: the best time to apply the fungi by the spore-spraying
method is when the larvae are young (that is in the first, second, and
third stages) and abundant. This time extends from April or earlier
until November and perhaps December. During a short time in .\lay
or June, just before and during the period of issuing of the secLond
brood of adult \vhitelies. when the progeny of the first brood ,c!e
mainly in lhe fourth larval and the pupal stages of development, but
little success can be expected. With the leaf-pinning and the tree-
planting mnetho:N, the best time extends from the date in March or
April when the adults begin to swarm about abundantly, until some-
time in September: after which but few adults are about. There
will be a short barren period for tle leaf-pinning method in May or
June. when few or no adults are about, and the larvae have advanced
to the older stages. W while successful growths of fungus can be
started during the fall months, yet they will generally not develop
and spread to any great extent until the following summer. It is
therefore desirable to get a good growth of ftngus started early in
the season, either in April or as soon as young larvae are abundant,
in order to benefit from the fungus as soon as possible. It may not
1:e possible, however, for want of n:aterial, to introduce fungus
beio(e the middle (f sunnmer or even later.
SUCCESS IN INTRODUCING THE FUNGI.
IlB taking into account the conclusions just set forth, and intro-
ducing the fungi in a methodical way, it should le possible to get a
good growth of fungus in nearly every trial. These conclusions are
based upon many experiments carried on during the past two years
and a half at Lake City. Leesburg. St. Petersburg, Kissimmee, New
Smyrna, DeLand and Gainesville. About fifty experiments have been
concluded, and several hundred trees have been treated. When the
conditions set forth in the preceding section were observed, so:ne
growth of fungus was invariably obtained when fresh fungus was
used, and when the spores were not injured bh the use of a spraying
machine contaminated with Bordeaux mixture.
Several citrus-growers have treated thousands of trees during
the past summer. \Among these, AIr. Frank Stirling, of DeLand, in
a communication of December 1, 190(), states that he has been suc-
cessful in starting the fungi, having sprayed between eight and nine
thousand trees with the red, yellow, and brown fungi since August,
19 i. le has also grown the red and brown fungi on infested cape
jasmine, chinaberrv and privet. Mr. H. B. Stevens, of DeLand,
reports that the application of the brown fungus by the spore-spraying
method in July has apparently resulted in infecting nearly all the
whitefly larvre. Leaves sent to the Experiment Station had every
larva killed by the fungus. Mr. Edwin W. Johnson, of East Palatka,







00 Florida -Agricultural Experiment Station

sends an account of his success in infecting the hir.-i. in his grove
with the red and brown fungi, and states that, in many cases, the
fungus growths on the sprayed trees were equal to those on the
leaves used for preparing the mixture of spores and water. lHe
expects to repeat the spore-spraying as soon as young larve are
present in the spring, and finds it an easy and inexpensive treatment.
EFFICIENCY OF THE FUNGI.
Our investigations show that the ii. 11 is not an insturlmount-
able obstacle to the profitable growing of citrus fruits. When left
without assistance, the fungi will practically destroy the whitefly in
a grove, on the average, once every three years; thus reducing the
injury due to the whitefly by at least one-third. The destruction is
not complete, so that the insects increase again during the two suc-
ceeding years; but this is accompanied by a rapid increase of the
fungi, until the whitefly is again overwhelmed. This is the
course run by the whiteily and the fungi when unassisted in
those sections which have been longest infested, such as lanatee
county, Fort Myers, and Orlando. At Orlando, the fungi were in
the ascendency during' the summer of l06(oi, and this resulted in so
far reducing the whitefly that an uncommonly large and clean crop of
citrus fruit was marketed in l!Dl;. The writer believes, however,
that by diligently following the recolunm nations made in this bulletin
it would he an easy matter to double the efficiency of the fungi; in
other words, to give us clean fruit on the average, for two years out
of three.
PLAN OF CAMI'AIGN.
The writer's plan of campaign, based upon experiments in the
field, is as follows: If a grove is thoroughly- infested with whitefy,
and sufficient seed-fungus is available, spray it thoroughly into all
the trees; but if the supply of seed-fungus is limited, spray only a
small amount into each tree. Later on, when abundant seed-fungus
can be procured, the trees or parts of trees not previously treated may
he attended to. A second, and even a third treatment may he given
to the trees in the same season in order to get the most thorough
dissemination of fungus. So long as only a few fungus pustules are
visible on those leaves of a tree which bear the most fungus and
'whitefly larvae, it will be advisable to introduce more, especially should
an abundance of seed-fungus be readily obtainahle. The greater the
amount of fungus growth which is successfully started in a grove, the
more rapid will be the destruction of the Il. Tl These insects
have a habit of congregating on water-sprouts and other tender
growth of citrus, consequently we should give particular attention to
introducing the fungi into such parts of the trees. The -work should
be done methodically and not in a haphazard way.
The plan of campaign for a grove just becoming infested with
whitefly, or only infested in part, would be to introduce fungus into







00 Florida -Agricultural Experiment Station

sends an account of his success in infecting the hir.-i. in his grove
with the red and brown fungi, and states that, in many cases, the
fungus growths on the sprayed trees were equal to those on the
leaves used for preparing the mixture of spores and water. lHe
expects to repeat the spore-spraying as soon as young larve are
present in the spring, and finds it an easy and inexpensive treatment.
EFFICIENCY OF THE FUNGI.
Our investigations show that the ii. 11 is not an insturlmount-
able obstacle to the profitable growing of citrus fruits. When left
without assistance, the fungi will practically destroy the whitefly in
a grove, on the average, once every three years; thus reducing the
injury due to the whitefly by at least one-third. The destruction is
not complete, so that the insects increase again during the two suc-
ceeding years; but this is accompanied by a rapid increase of the
fungi, until the whitefly is again overwhelmed. This is the
course run by the whiteily and the fungi when unassisted in
those sections which have been longest infested, such as lanatee
county, Fort Myers, and Orlando. At Orlando, the fungi were in
the ascendency during' the summer of l06(oi, and this resulted in so
far reducing the whitefly that an uncommonly large and clean crop of
citrus fruit was marketed in l!Dl;. The writer believes, however,
that by diligently following the recolunm nations made in this bulletin
it would he an easy matter to double the efficiency of the fungi; in
other words, to give us clean fruit on the average, for two years out
of three.
PLAN OF CAMI'AIGN.
The writer's plan of campaign, based upon experiments in the
field, is as follows: If a grove is thoroughly- infested with whitefy,
and sufficient seed-fungus is available, spray it thoroughly into all
the trees; but if the supply of seed-fungus is limited, spray only a
small amount into each tree. Later on, when abundant seed-fungus
can be procured, the trees or parts of trees not previously treated may
he attended to. A second, and even a third treatment may he given
to the trees in the same season in order to get the most thorough
dissemination of fungus. So long as only a few fungus pustules are
visible on those leaves of a tree which bear the most fungus and
'whitefly larvae, it will be advisable to introduce more, especially should
an abundance of seed-fungus be readily obtainahle. The greater the
amount of fungus growth which is successfully started in a grove, the
more rapid will be the destruction of the Il. Tl These insects
have a habit of congregating on water-sprouts and other tender
growth of citrus, consequently we should give particular attention to
introducing the fungi into such parts of the trees. The -work should
be done methodically and not in a haphazard way.
The plan of campaign for a grove just becoming infested with
whitefly, or only infested in part, would be to introduce fungus into







Bulletin 97


all those trees sufficiently infested (that is, a score or more of larvae
on each leaf), and later on into other trees as soon as they become
sufficiently infested. This operation should be repeated each year, or
whenever the whitefly is observed to be in sufficient abundance to
allow of a good growth of fungus being started.
WHERE FUNGI MAY BE BOUGHT.
The Experiment Station has no funds available for collecting
and distributing fungi. The money appropriated by the U. S.
Congress for the maintenance of Experiment Stations is for the
purpose of defraying the expenses of actual experiments and investi-
gations pertaining to agriculture. As the collecting and distributing
of well-known fungi is not an experiment, it could not be carried
on with this money. The State Legislature would appropriate money
for such work, if the citrus growers considered it desirable to do so.
But sufficient fungus material can generally be obtained from private
sources. The following gentlemen have consented to furnish fungus
whenever they have it available. The cost will vary, but from two to
four dollars will generally pay for an amount sufficient to treat an
acre of grove. Red, yellow, and brown fungi: C. A. Boone. Orlando,
Fla. Red and brown fungi: A. J. Pettigrew, Manatee, Fla.; A. F.
Wyman. Bradentown, Fla.; F. D. Waite. Palmetto, Fla. Red and
yellow fungi: C. B. Thornton, Orlando, Fla. Red fungus: Frank H.
Davis, Apopka, Fla.; John F. Carlton. Sparr, Fla. Yellow fungus:
W. H. Maxwell. Titusville, Fla. It may be mentioned here that
3,000 orange leaves will loosely fill a bushel measure.
THE FUNGI.
RED FUNGUS OF WHITEFLY.


Fig. 2. Red Fungus of Whitefly. xly.







Bulletin 97


all those trees sufficiently infested (that is, a score or more of larvae
on each leaf), and later on into other trees as soon as they become
sufficiently infested. This operation should be repeated each year, or
whenever the whitefly is observed to be in sufficient abundance to
allow of a good growth of fungus being started.
WHERE FUNGI MAY BE BOUGHT.
The Experiment Station has no funds available for collecting
and distributing fungi. The money appropriated by the U. S.
Congress for the maintenance of Experiment Stations is for the
purpose of defraying the expenses of actual experiments and investi-
gations pertaining to agriculture. As the collecting and distributing
of well-known fungi is not an experiment, it could not be carried
on with this money. The State Legislature would appropriate money
for such work, if the citrus growers considered it desirable to do so.
But sufficient fungus material can generally be obtained from private
sources. The following gentlemen have consented to furnish fungus
whenever they have it available. The cost will vary, but from two to
four dollars will generally pay for an amount sufficient to treat an
acre of grove. Red, yellow, and brown fungi: C. A. Boone. Orlando,
Fla. Red and brown fungi: A. J. Pettigrew, Manatee, Fla.; A. F.
Wyman. Bradentown, Fla.; F. D. Waite. Palmetto, Fla. Red and
yellow fungi: C. B. Thornton, Orlando, Fla. Red fungus: Frank H.
Davis, Apopka, Fla.; John F. Carlton. Sparr, Fla. Yellow fungus:
W. H. Maxwell. Titusville, Fla. It may be mentioned here that
3,000 orange leaves will loosely fill a bushel measure.
THE FUNGI.
RED FUNGUS OF WHITEFLY.


Fig. 2. Red Fungus of Whitefly. xly.








52 Florida Agricultural Experimcut Station

As the name implies, this fungus is red and when at its height
of spore-formation bright red, this extra redness being due to the
mass of spores. Before it reaches the spore-producing stage, it is
yellowish in color, and becomes a faded pink when the spores have
been washed away. This fungus growth or pustule is generally sur-
rounded by a lighter-colored fringe closely appressed to the leaf,
while the pustular part projects. The exact details of the process by
means of which a whitefly larva becomes infected by this fungus
have not been observed, but that the infection proceeds from the
development of a spore of the fungus, lodged on or near the larva,
has been demonstrated beyond doubt by hundreds of experiments
with the spore-spraying method. Figures 3-5, taken from Dr. IH. J.
Webber's bulletin., show many details in regard to the manner of
development of this fungus in the body of the il larva.


P.: ..t W. .. 1 :




A.S, 1)




Tr. V after Webber.) Fii 4. (After Webber.)
larva wlilhi ed Lnter tage. The fungnli Fig. 5. IAfter \Vehher.) Still
fulnguls *.' -' l Thread are seen ulno later .st a e The spore-
sideits ,. I i. i.. ingtolmtofthedead lar'Va. Imasss fOr'Il a lloken ring
is dying or dead. X 1). X lb. ronnd the dead u tlrv; X 15.

This fungus appears to thrive equally on both species of the citrus
whitefly, but has most frequently been observed upon the species with
the smooth -. (Alcyrodcs citri). The red fungus can be introduced
by any one of the three methods already described, and is very
effective. It requires about three weeks for this fungus to make
visible growth, but under the most favorable conditions growth has
several times been detected in ten days.
YELLOW FUNGUS OF WHITEFLY.
This fungus is so much like the red fungus that what has been
written and figured in regard to the latter holds true for the former.
Its color, however, is a rich lemon yellow, so that it can easily be dis-
tinguished from the red, especially when both are in the spore-pro-
ducing stage. It was first described from specimens obtained on
guava leaves in Brazil, and was first recognized in Florida by Pro-
fessor P. H. Rolfs in September, 1906. This fungus appears not to
thrive so well upon the smooth-egged species (Aleyrodcs citri) of the







Bulletin 97 53

citrus whitefly. Whenever the writer observed it effectively infecting
whitefly larva, it was on the species with reticulated eggs. All efforts.
on the part of the writer to introduce it effectively on the species with
smooth eggs have so far failed. It has been found possible to infect
a few larvae, but the fungus did not increase and thrive, and this.
happened when the red fungus, introduced at the same time and close
by, grew and throve well. This fungus can be introduced by any of
the three methods and has been observed to be very effective on the
whitefly with reticulated eggs (Aleyrodes nubifera). The spore-spray-
ing method is to be preferred.
BROWN FUNGUS OF THE WHITEFLY.
This fungus develops into pustules of a glossy chocolate brown,
although sometimes it is quite light in color. It resembles in color
and shape the Florida red scale of the orange, Chrysomphalus
(Aspidiotus) ficus, and may easily be mistaken for this insect. The
brown fungus differs in one remarkable respect from all the other
known fungus parasites of the whitefly. The fungus growth which
develops upon a single whitefly larva, instead of being limited in its.
activities to this one larva, sends out hundreds of ramifying fungus-
threads hyphaee), which will infect other larva if they are sufficiently
near. From these infected larvae more threads ramify until the whole
under surface of the leaf is covered with a network of fungus threads,
which when peeled off, has much the appearance of very thin tissue















Fig. 6. Brown Fungus of Whitefly. xl .
paper. This fungus tissue may also spread to the upper surface of
the leaf and down along the leafstalk, even onto the stems of the
twigs.
The brown fungus appears to thrive on both species of whitefly,
but has been more frequently observed upon the smooth-egged species
(Aleyrodes citri). It has been successfully introduced by means of







Florida Agricultural Experiment Station


all the methods described on a former page; but since the red and
yellow Aschersonias lend themselves more readily to experimentation
because of the ease with which their spores may be obtained, these
have naturally been experimented with first, possibly to the neglect
of the brown fungus. That the latter can readily be introduced onto
non-infected whitefly larvae by the spraying method, has been demon-
strated a number of times by the writer and others. The most suc-
cessful of these introductions have probably been made by Mr. H. B.
Stevens, at DeLand, during July, O190, and by Mr. Edwin NW. Johnson,
at East Palatka. Experiments so far indicate that we have the most
favorable conditions for introducing the brown fungus during July
and August. Until more definite information in regard to the spores
of this fungus is at hand, the writer recommends that the fungus be
scoured off the leaves by means of a little sand and water, and the
resulting mixture of fungus particles and water used as a spray.
About the same relative quantities of fungus and water should be
taken as recommended for the red and fellow Aschersonias, and if
necessary the mixture may be strained.

WHITEI-lRINGE FUNGUS 01 WIIIJ0EFLV.






j,.,. e ...- sX,


.tr .- : ," 5,


72L "',-'^ "




Fig. 7. White-fringe Fungus on Whitefly (Ale/rodtes nitlifera).
Sooty mold round several larve.
This fungus has been only recently recognized as an effective
parasite of whitefly larvme.2 It was observed that from 70 to 90 per
cent. of the larvae in certain trees were dead, apparently through
infection by this fungus. The white-fringe fungus is not conspicuous
to the unaided eye, as are most of the other fungus parasites of the






Bulletin 97 55

whitefly, but it can be made out with the use of a hand lens. It
appears as a delicate white fringe about the margin of the larva, which
fringe soon disappears when the leaves dry. The dead larva have a
white or light-pink papery appearance.
The fungus has been successfully introduced by the spore-spray-
ing method, and in two weeks it was plainly evident upon previously
healthy larvae-in this instance, those of the smooth-egged species
(Aleyrodes citri). The fungus can probably also be introduced by
the other methods. It will apparently thrive on both species of
whitefly, but has so far been observed as most effective upon the
species with reticulated eggs (Aleyrodes lnbifera). This fungus
being of comparatively recent discovery, and being besides rather
evanescent and inconspicuous, much remains to be observed in reganr.
to its life-history and its effectiveness in checking the whitefly. It
seems to be pretty generally distributed in the citrus-growing sections
of the State, as specimens have been identified from widely separated
groves.
CINNAMON FUNGUS OF WHITEFLY.


















Fig. 8. Cinnamon Fungus on Whitefly. x 1%.

This fungus much resembles the brown fungus, except that the
surface of its pustules has a powdery appearance and a cinnamon-
brown color. A layer of white interwoven threads spreads a little
distance over the leaf from the pustules, but this layer does not
spread over the whole leaf, as it does for the brown fungus. The
cinnamon fungus produces an abundance of spores, and may be
introduced by the spore-spraying method. It appears to be widely
distributed in small quantities and on both species of whitefly. While







-56 Florida Agricultural E.perimeIn Station

this fungus is useful, and may frequently he introduced, especially
in connection with the brown fungus, yet it does not occur in sufficient
abundance to allow of its Ibeing preferred to the brown fungus or to
the Aschersonias. It has also been observed on several scale insects
including a Lecanium and a Diaspis.
SPOROTRICHUil FUNGUS o0 W\VITEIFLY.
This Sporotrichuin is a species of fungus closely related to the
chinchbug fungus. The plant pathologist of the Station, Prof. H. S.
Fawcett, has several times observed this flngus on adult whiteflies
in different parts of the State, first in a small orange grove near
'Gainesville during last August. Dozens of the adults were found
-dead, attached to the under surface of the leaves, with the grayish
fungus threads penetrating the body-wall and bearing thousands of
.spores. As just stated, this fungus infects the adults, but it has also
been observed on the larva. It has so far been found only on the
species of -.lhr..i1 with smooth eggs (Alcvyrodcs citri). This fungus
may prove to be a valuable adjunct to the other fungus parasites,
especially since it attacks the adults, which the other fungi are not
known to do.
FUNGUS SUPEIRPARl'ASITES.
/Cladosporiomr sp.-An olive-green fungus of the genus Clado-
sporium frequently overruns and destroys the red and I1.. Ascher-
sonias, changing their colors to olive-green. Attention was first
directed to this fungus by Dr. A. W. Alorrill in an article to the
Tilms-Union, of Jacksonville. Fla., April 14, 1907. According to the
present writer's observaticns, this fungus strongly attacks the red and
yellow Asclersonias only towards fall and during winter and spring,
when these fungi are inactive and are probably undergoing degener-
:ative changes. The chief injury caused by the Cladosporium, in the
writer's opinion, may consist in its destruction of the spores of the
Aschersonias, at a time when these should be conserved for the infec-
tion of the spring brood of I ,, i larvae. The writer is not aware,
however, that the Aschersonias are seriously retarded by the Clado-
sporium, since their spores are in a great n,'sasure lost, in any case, by
the weathering and rain of the winter and spring. At all events, the
writer has so far given no heed to the Cladosporium in conducting his
experiments. The yellow Asehersonia is more generally infected by
the Cladosporium than the red Aschersonia. This Cladosporium also
occurs on dead insect remains, and may overrun the sooty mold
fungus.
Coniiothr'izrm sp.-Shortly after Dr. Morrill had noticed the
Cladosporium, he directed the writer's attention to another fungus in
Manatee county, which he believed to he a superparasite of the
brown fungus. It was identified by Prof. II. S. Fawcett, as belonging
to the genus Coniothyrium. It occasionally overruns the pustules of







Bulletin p7 57

the brown fungus, and much resembles a certain stage of the black
scale fungus, Myriangium Duriaei, but it has a decided shade of green
in the black. The writer regards this fungus also as attacking the
brown fungus chiefly after the latter has become old or weakened from
drought or cool weather.
SOOTY MOLD.
This mold (a species of Meliola) is of a sooty black color, as its
name implies. It is found whenever whitefly or other insects occur
that excrete a sweet solution (honeydew). As this honeydew nearly
always collects on the upper surfaces of leaves, it follows that the
mold which thrives in this secretion occurs mainly on the upper
surface. Insects that are accompanied by the sooty mold are: whitefly,
mealybugs, plant lice aphidess), soft scales (Lecanium), wax scales,
cottony cushion scale, etc. The presence of sooty mold on a tree is
therefore not a sure sign of the presence of whitefly. This fungus
does not ordinarily become visible until after the trees have been
infested by the whitefly for some months. Not infrequently this sooty
mold occurs also on the under surface of the whitefly-infested leaves,
either completely covering them or forming a black fringe about
whitefly larva ( Fig. 9). When this condition occurs, it is due, in
the first place, to an abnormal or diseased state of the larvae, which
results in the honeydew collecting about and underneath them, instead
of being projected away. The mold then develops in this honeydew,
and probably completes the destruction of the larva. Larvae wet with
their own honeydew are frequently observed before the mold has
made any visible growth. Sometimes the diseased condition of the
larve resulting in this wetting is recognized as being due to an infec-


Fig. 9. Sooty Mold overgrowing Whitefly (.llrndes citri).
Also eggs, larvae, and pupa cases. x 1-%.






58 Florida Agricultural Experiment Station

tion with one of the fungus parasites of the whitefly, but at other times
no cause can be assigned.

ARTIFICIAL MEANS OF CONTROL.
SPRAYING WITH CONTACT INSECTICIDES.-For more complete
directions in regard to the preparation of contact insecticides, the
reader is referred to Bulletin 7 ( of the Florida Experiment Station,
on Insecticides and Fungicides, which also contains general directions
for spraying and fumigation. Judicious spraying with contact insecti-
cides would be effectual in reducing the ravages of the 1i-., i pro-
vided a grower can persuade his neighbors to spray at the same time.
or if the grove is isolated. If a grove is not isolated and one's neigh-
bors do nothing to check the whitefly, the latter will kee) coming in
from the infested trees. When chinaberry trees, privet, or other
food plants are about to aid in the breeding of the adults, an isolation
of a mile will hardly be sufficient to keel) whiteflies from coming in
when they begin to swarm out of such trees as chinaberry and um-
brella trees during August and September. Spraying is difficult and
almost impracticable, except when the trees are small-not over five
to seven years old-since the larger the tree, the more difficult it is to
do the work thoroughly.
December, January and February are the best months to spray
for the whitefly, as this insect is then in one or other of its larval
stages, and there are very few or no adults present to escape. It is
practically useless to spray the adults, since the females may lay their
eggs when they are eighteen to thirty hours old, so that the grower
would have to spray every day (during the swarming periods to insure
killing them before they laid their eggs. The eggs are not readily
killed either by spraying or fumigation. Spraying to be most effective
should, furthermore, be really thorough, and one such spraying in
winter, after the fruit is picked, will be worth more than several less
thorough applications. The spraying should be postponed until
danger from frost is past: since if the leaves should be cut off by a
frost, but little if any spraying would be necessary during that season.
Summer spraying may be practiced when conditions require it. The
difficulty with spraying lies not so much in getting an insecticide that
will kill the insect, as in the application of it so that all, or at least
a very large percentage of the whitefly larvae will be killed. Any of
the contact insecticides, such as whale-oil soap, kerosene emulsion,
resin wash, and a number of proprietary brands which are generally
used for destroying insects on citrus leaves, will be found effective.
However, all spraying with emulsions and other chemical compounds
generally in use is more or less injurious to orange trees. Of these.
whale-oil soap is probably the least injurious. Before spraying, all
excessive foliage should be removed from the trees by a thorough
pruning. Spraying with insecticides is also more or less harmful to







Bui!ctil 97 '9

the fungi; so that having once decided to adopt the fungus method,
spraying should be discontinued. Soap solutions and plain emulsions
of oils do least injury to the fungi, unless used in a very concentrated
form.
FUMIGATION WITH HYDRIOCYANIC ACID G.\s.-Those desiring
information on fumigation are referred to the bulletin on this subject
by Dr. A. WV. Morrill.?' Those who require copies of this bulletin
may secure them through their congressmen. Dr. Morrill says
further in the "Florida Fruit and Produce News," November ?0,
1908: "In the country if a grove is isolated by a distance of two
or three hundred feet from all other infested groves, fumigation can
be practiced without fear of its being made unprofitable by migrations
of the adults."
QUARANTINE.
The whitefly can be kept out of non-infested groves in localities
sufficiently isolated, for a considerable length of time. The fact that
thousands of dollars may be saved in this way to a grower or a com-
munity, should be an incentive for all, whether directly interested
or not, to co-operate in keeping the whitefly out, or in checking its
spread.
Several methods of procedure are available. 1yv closing all pri-
vate roads and gates, especially against vehicles coming from infested
districts, much could be, and in fact has been, accomplished. The
property should be "posted." which would have the effect of keeping
out many individuals who may be carriers of whitefly, since the
latter has frequently been found concealed on the clothing of persons
after they had left infested localities. No nursery stock should be
admitted except after it has been completely defoliated (leaf and
leaf-stalk), and cut back to the extent of removing the tender green-
colored growth. To complete the protection, the stock should further-
more be fumigated with hydrocyanic acid gas. When it is known
for a certainty that the section from which the stock is ordered is
free from H- i. I, the previous precautions need not be taken; but
the stock should be completely enclosed to protect it from becoming
infested while in transit through infested districts. Pickers' imple-
ments from infested districts have been excluded by growers in cer-
tain non-infested sections. This was a perfectly proper course to
follow, since it is easy to conceive of the newly hatched larva or the
adults being carried by such means. Such iimpllements could, how-
ever, be made safe by a thorough spraying with some contact insecti-
cide. When implements are sprayed, every effort should be made to
saturate all crevices. The picking bags and outer clothing of pickers
should also be treated, either with carbon bisulphide or with hydro-
cyanic acid gas, in some air-tight receptacle or room. Three ounces
(about one-fifth of a pint) of carbon bisulphide will be sufficient to
fumigate a space about the size of a barrel, the fumigation being







Florida Agricultural E.periment Station


allowed to continue from thirty minutes to several hours. If a fumi-
gating box is at hand, such as is used for fumigating nursery stock,
the implements and other objects may be fumigated in this, using
an ounce of potassium cyanide, two ounces of sulphuric acid and
four of water. The water and acid are first mixed in an earthen-
ware vessel of double the necessary capacity, and then the cyanide
is added. The gas is evolved immediately, and is dangerously poison-
ous. The fumigation should last for thirty minutes or longer. The
picking bags and clothing of the pickers should be arranged loosely
and with spaces between them to insure a circulation of the vapor
or gas used for fumigating. See bulletin 76 of the Bureau of Ento-
mology.5 and bulletin 76 of this Station, for further directions on
the use of hydrocyanic acid gas.

FOOD PLANTS OF THE WHITEFLY.

Some people still imagine that every tree. bush, and shrub in
our hammocks is a food plant for the whitefly. This is erroneous.
The number of food plants is very limited when compared with the
number of native species of plants. As a matter of fact, the native
species capable of supporting the ,,in. il in dangerous quantities
are quite few. The number of plants, however, which become only
occasionally infested, may be greater than we at present know.
CLASS I.-FrooD PLANTS PREFERRED BY THE WHITEFLY.
Native Species:
Prickly ash (Fa.tara Ch',va-Hcrculis).
Wild persimmon ( Diospvros Virginiana ).
Introduced Species:
Citrus (all varieties).
( In, h.I. r (Melia Ascvedarach).
Umbrella (Mclia A-crdarach i inbract/lifcra).
Cape jasmine (Gardenia jasm inoidcs).
Privets (Ligitstrumn spp.).
Japan persimmon (Diospyros Kaki).
CLASS II.--OOD PLANTS SOMETIMES INFESTED IUT NOT PREFERRED
BY THIE WIIITEFLY.
Native Species:
Cherry laurel or Mock orange (Lalroccrasis sphaerocarpa and
L. Caroliniona).
Smilax (Siila-r sp.).
Blackberry (Rubus sp.).
Water Oak (Qucrcus nigfra).
Scrub palmetto (Sabal iegacarpa).
Viburnum nudum.







BuHltirn 97


Introduced Species:
Coffee (Coffea Arabical .
Pomegranate ( Piunica granatiin).
Allamanda (I llamaindi ncriifolia ).
Honeysuckle ( Loniccra japo iiiL Ha/lliala ).
Ficus altissirma.
Ficus sp. (from Costa Rica .
Oleander (Vcriitt Olnan cdcr).
Cultivated pear ({Pv'rus sp.).
Lilac Syringa sp.).
Banana shrub (ilich/ia ftiscata).
Camellia, often called Japonica, ( Ccellia Japoniica).
PrickI-, ash and imcck orange have again been observed in-
fested with whitefly during October. 1ll9., both at Lake City and
at Gainesville. and the former has been put in Class I. Both are
undoubted food plants, but the latter is less frequently infested. A
pomegranate 1ush, growing near infested citrus trees in a small
grove at Leesburg, was observed to be thoroughly infested during
December. 190(., and again in August. I''1 ---. I;, 'l. in all stages
being present at the time of the second observation. Coffee, alla-
manda, ....l. i, and banana shrub were observed at Lake City
in October. 19t-S, and found variously infested with whitefy. The
coffee tree was thoroughly infested, having as many eggs on its
leaves as citrus trees mav have. All larval stages and the pupe
were also observed but no empty pupa-cases. Eggs and larvne were
abundant on the allamanlda and a few empty pupa-cases were also
found, indicating that some whiteflies had matured. Eggs and first-
stage larva: cmlv were foolnd on the camellia, but some eggs with
all four stages of larvae were on the banana shrub, together with a
doubtful pupa-case. Several larva' and two empty pupa-cases were
found on smilax near a chinalerrv tree in a small grove by Gaines-
ville, in August, 1908. Blackberry and honeysuckle are reported as
host plants of I1i. 1 larv-e in winter, hb Dr. E. H. Sellards in the
Annual Report of the Florida Experiment Station for 1905. The
water oak has been reported as a food plant ba v Quaintance and
Gossard, but it is nct stated that the insect ever reaches maturity
on this tree. The writer has never been able to find either eggs or
larv;e on oaks. Professor Gossar d also mentions having' taken two
or three larvre advanced to the third and fourth stage on scrub pal-
metto,3 but the writer has so far been unable to duplicate the observa-
tion. Oleander, cultivated pear and lilac are listed by Dr. Morrill."
PLANTS TO BE CONDEMNED.
The following plants should be destroyed by every citrus grower,
and by all the people in every community where citrus growing is an
industry. These plants are, the cape jasmine, the chinaberry tree,
the umbrella tree, the prickly ash. all privets, the trifoliate orange







62 Florida Agricultural Experiment Station

(Citrus trifoliata), and any useless and abandoned citrus trees. The
mock orange, or cherry laurel, should also be included in this list
whenever it is observed to become infested. These plants are gen-
erally of little value, and can well be surrendered and replaced by
others not subject to attack by whitefly. They should be cut down
and immediately burned to prevent the I!i. -0, from transforming
and migrating to other food plants. It may seem akin to vandalism
to sacrifice some of the ornamentals, but all successful warfare con-
sists, in some degree at least, in reducing the number of the enemies'
strongholds. One cape jasmine and two or three umbrella trees in
a certain yard in New Smyrna appear to have been responsible for
the spreading of the whitey in that place, and the consequent loss
of hundreds of dollars, while the plants themselves were not worth
a thousandth part of the cost of the damage.
( n1 11. 1 IT and umbrella trees are no doubt the two food plants
of the whitefly which are most to be feared by citrus-growing com-
munities. It has been observed that the adult whitefies instinctively
leave these trees in August and September, or at the time when the
fall brood of adults matures. This accounts for the great number
of adults which swarm about the trees of some of our towns and in
their immediate vicinity. Alyriads of adults were observed during
August and September, 1908, fully a mile from their presumed breed-
ing places in and about Gainesville. The citrus trees on the Experi-
ment Station grounds, which were previously free from whitcHy, be-
came literally alive with them. These citrus trees are at least a mile
from the nearest chinaberry and umbrella trees previously infested
with whitefly. The adults were observed everywhere, in houses, on
windows, and on garments; and some plants, such as collards and
beans, which are not food plants, were swarming with them, but no
eggs or larvae were discovered on these plants. Examination during
autumn of the leaves of some of the infested umbrella trees in Gaines-
ville, as well as in several other towns, revealed the fact that rela-
tively few eggs (only a dozen or two per leaf) were being deposited
on these, while the leaves of citrus and privet were covered with
thousands of e-ggs. In spring the situation is reversed, and then
some of the whiteflies migrate to the chinaberry and umbrella trees
from such evergreens as cape jasmine, privet, and citrus.
WHITEFLY LIVING ON FALLEN LEAVES.
While making inspections of 1, 1i. i -,iested trees at DeLand.
on November 20 and 21, 1907. the writer, with the aid of Mr. R. Y.
\Winters, Assistant in Botany at the Experiment Station, made careful
examinations of considerable quantities of dead and dried leaves
found under cape jasmine and citrus trees. Special attention waa
given to those leaves found in small hollows, or otherwise somewhat
protected against complete drying up. The result was that well-
matured larve and pupe, apparently healthy and alive, were found







Bulletin 97 63

on dead and brown leaves, which had either retained, or had been
supplied with, sufficient moisture to keep them flexible. Also a liv-
ing adult was found emerging from its pupa case. Some of these
leaves were taken to the laboratory at the Experiment Station, and
after a few days winged whiteflies emerged. On January 17, 1908,
some of the fallen leaves under the cape jasmine were again exam-
ined, with similar results. Several fresh leafy twigs were collected
at DeLand from the cape jasmine and taken to Gainesville. Some
were placed in a cloth sack, and lightly covered w'.ith earth at the
foot of a magnolia tree. Live whiteflies emerged on March -2, when
some of the leaves were still green. Other twigs were kept under a
helljar with open top, covered with cheesecloth. on moist sand in
the greenhouse. Live adults were obtained at the end of tw o months,
and a few of the leaves were still green. There remains no doubt.
therefore, that some whitefly larvae and pupce can continue to live
on leaves that have dropped from the trees during winter, and that
these may mature sufficiently late in the spring to infest the new-
leaves.
RESULTS OF DEFOLIATION.
It appears from the observations just stated, that one cause of
the reinfestation of the citrus trees after defoliation at Deland dur-
ing the summer of 190; was the presence of live whitefly larv;e and
pupte on some of the fallen leaves beneath the trees. All infested citrus
and other food plants at DeLand had been carefully defoliated during
February, 19107, after the partial defoliation by frost in the previous
December, and precautions had been taken to burn the leaves. No
doubt, however, some leaves were overlooked. Some of the trees in
which the whiteHfi reappeared in greatest abundance had been banked
-ith earth, and these banks must have been appropriate places for
preserving leaves with live larvxe and pupae. It is, of course, possible
that some whitefly lived over the winter on other plants, but careful
search in November and January revealed no plants witl whiteHly on
them. Nevertheless, defoliating the trees at Deland was productive
of much good, and prevented a damage that would have equaled
many times its cost. The results were equal to a season's spraying,
or one fumigation.
Defoliation as a means for checking the whitefly in a grove can
hardly be recommended, except when the defoliation has already
been in a great measure accomplished by a preceding freeze, or when
one has only a few small trees. The best time in which to defoliate is
probably in January or February, before the trees start to grow.
HIONEYDEW.
A convenient method for collecting honeydew consists in placing
a Icaf infested with -.. iw. i, larvae between two glass plates, or on a
glass plate or other smooth surface, so that the honeydew projected
by the larvae will fall upon the glass or other surface. The honeydew







Bulletin 97 63

on dead and brown leaves, which had either retained, or had been
supplied with, sufficient moisture to keep them flexible. Also a liv-
ing adult was found emerging from its pupa case. Some of these
leaves were taken to the laboratory at the Experiment Station, and
after a few days winged whiteflies emerged. On January 17, 1908,
some of the fallen leaves under the cape jasmine were again exam-
ined, with similar results. Several fresh leafy twigs were collected
at DeLand from the cape jasmine and taken to Gainesville. Some
were placed in a cloth sack, and lightly covered w'.ith earth at the
foot of a magnolia tree. Live whiteflies emerged on March -2, when
some of the leaves were still green. Other twigs were kept under a
helljar with open top, covered with cheesecloth. on moist sand in
the greenhouse. Live adults were obtained at the end of tw o months,
and a few of the leaves were still green. There remains no doubt.
therefore, that some whitefly larvae and pupce can continue to live
on leaves that have dropped from the trees during winter, and that
these may mature sufficiently late in the spring to infest the new-
leaves.
RESULTS OF DEFOLIATION.
It appears from the observations just stated, that one cause of
the reinfestation of the citrus trees after defoliation at Deland dur-
ing the summer of 190; was the presence of live whitefly larv;e and
pupte on some of the fallen leaves beneath the trees. All infested citrus
and other food plants at DeLand had been carefully defoliated during
February, 19107, after the partial defoliation by frost in the previous
December, and precautions had been taken to burn the leaves. No
doubt, however, some leaves were overlooked. Some of the trees in
which the whiteHfi reappeared in greatest abundance had been banked
-ith earth, and these banks must have been appropriate places for
preserving leaves with live larvxe and pupae. It is, of course, possible
that some whitefly lived over the winter on other plants, but careful
search in November and January revealed no plants witl whiteHly on
them. Nevertheless, defoliating the trees at Deland was productive
of much good, and prevented a damage that would have equaled
many times its cost. The results were equal to a season's spraying,
or one fumigation.
Defoliation as a means for checking the whitefly in a grove can
hardly be recommended, except when the defoliation has already
been in a great measure accomplished by a preceding freeze, or when
one has only a few small trees. The best time in which to defoliate is
probably in January or February, before the trees start to grow.
HIONEYDEW.
A convenient method for collecting honeydew consists in placing
a Icaf infested with -.. iw. i, larvae between two glass plates, or on a
glass plate or other smooth surface, so that the honeydew projected
by the larvae will fall upon the glass or other surface. The honeydew







64 Florida Agricultural Experiment Station

is deposited in small drops, and in case the glass is above the larve
it may be projected upwards for a distance of one-eighth of an inch.
Pupa ready to transform into adults secrete honeydew, as do larve
of all stages. Larvae of probably the third and fourth stages of
growth excreted at the rate of .0003 granmme each in 48 hours. One
million larve would thus excrete about a pound of honeydew in 48
hours. This would be at the rate of 15 pounds per month, or 180
pounds per year. \hen we recall that thousands to millions of
whitefly larve may inhabit one tree, we get some idea of the amount
of sap stolen from an orange grove by this pest.
LIFE HISTORY OF WHITEFLY.
(Figs. 1, 9, 10, 11, 12-19.)
The name whitefly is a misnomer, the insect in question not
being a fly, hut a member of the order Hemiptera, to which the plant-
lice and scale insects belong. The fact that the whitefly has four
wings at once separates it from the order Diptera, or flies proper.
There are three well-defined broods of whitefly, with an interva:
between each brood of several days to several weeks, when few oi
none are seen on the wing. The first brood generally appears some
time in March, April, or May, varying with the latitude and with
the temperature of the spring. The second brood emerges in June.
July, or August. and the third in August, September or October.
Some people have supposed that they had exterminated the whitefly
by some treatment (such as the application of copperas), when one
or other of the broods had disappeared from the wing.
Larv;e (the young stages) or pupas (the transformation stage)
of the i-.! can nearly always be found on the under surface
of the leaves. The larvae are scale-like (Figs. 9, 11, 14-18), and
closely appressed to the leaves. They vary in size from the recently
hatched larva, just visible to the unaided eye, to the full-grown
larve, which are one-cighteenth of an inch in length. The larva.
are light-colored, with a tinge of yellow, translucent, and almost in
visible on the leaf. By rubbing the under surface of a leaf length-
w-ise with the finger, the larv;e will appear as flattened whitish scales.
The pupa (Figs. 9 and 11) is the transformation stage from the larva
to the adult winged insect. The pup;e are readily visible as yellowish-
white, plump, oval bodies, with a dark reddish spot on the back. From
the pupa emerges the adult wiinged fly. The little white cases, with
a T-shaped split on the back, found on the under surface of the leaf,
are the empty pupa-cases from which the adults have emerged ( Figs.
9 and 11). The eggs (Figs. 1, 9. 10. 12 and 13) are just visible to
the unaided eve as a fine dust on the under surfaces of the leaves.
An ordinary hand lens or magnifying glass will show them as little
bodies resembling grains of wheat. There are, therefore, four stages
in the life of the whitefly: the egg, visible as a fine particle of dust;





Bulletin 97 65







i' \ \










:7

-N




AL10 110
Fig. 10. (From Bul. 67.) Whitefly (Aleyrodes citri) and insects sometimes mis-
taken for it. Much enlarged. No. 1. Female whitefly with expanded wings.
No. 2. Female whitefly with folded wings. No. 3. Egg and footstalk. No.
4. Empty eggshell. No. 5. Tip of abdomen of male showing claspers.
No. 6. Antenna of whitefly. No. 7. Front margin of forewing of whitefly.
No. 8. Larva of guava whitefly (Aleyrodes floridensi.). No. 9. Margin, and
No. 10, wax fringe, of larva of guava whitefly. No. 11. Soft scale (Lecanium
hipperidum.)








Florida Agricultural Experiment Station


a-


IN j l

\rel


Fig. 11. (From Bul. 67.) Larval and pupal stages of whitefly (Aleyrodes citri).
No. 1. First stage larva, much enlarged. No. 2. First stage larva. No.
3. Second stage larva. No. 4. Third stage larva. No. 5. Fourth stage
larva. No. 6. Margin of advanced larva, much enlarged. No. 7. Orifice
of fourth stage larva, much enlarged. No. 8. Pupa, showing orange-col-
ored areas, and wax tufts from breathing tubes. No. 9. Adult whitefly,
with wings folded up, emerging from pupa skin. No. 10. Empty pupa case
with T-shaped slit.


I -~








V






Bulletin 97


the larva, a flattened scale; the pupa, plump and easily seen; and the
adult winged insect. These stages are nearly always found on the
under surfaces of the leaves.
The following facts are taken from Prof. H. A. Gossard's
bulletin : Twenty thousand eggs have been estimated on a large
orange leaf. From observation made in the laboratory, egg-laying
begins when the female is from eighteen to thirty hours old, and
from seventeen to twenty-five eggs are deposited. [The number of
eggs is doubtless greater.] The length of life of the female has been
estimated at from three days in warm weather, to three weeks in
cool weather, and the complete length of the life cycle from egg
to adult at from forty to fifty days in summer to six months in
winter.
This brief summary of the life-history of the whitefly applies,
in its details, to the species with smooth eggs (Aleyrodes citri); but
also in a general way, as far as is known at present, to the species
with reticulated eggs (Alcyrodcs nubifera).


Fig. 12. Eggs and eggshells of Aleyrodts nubi-
fera. Netted surface and wide opening.
Enlarged about 90 times.
TWO SPECIES OF CITRUS WHITEFLY.
(Figs. 1, 9, 10, 11, 12-19.)
There are two distinct species of the citrus whitefly of Florida,
each of which seriously infests citrus trees. In order to facilitate






Florida Agricultural Experiment Station


reference to the two species in question, it should be stated that the
species with the smooth eggs is Aleyrodes citri, Riley and Howard. It
is to this species alone that the citrus whitefly of Florida has until re-



















Fig. 13. Eggs of Aleyrodes citri. Smooth sur-
face. Enlarged about 90 times.

cently been referred. The other species, with reticulated eggs, has now
been named, Aleyrodes nubifera n. sp. The reticulated egg was figured
in 1893, by H. A. Morgan, in a special bulletin of the Louisiana Experi-
ment Station.4 Attention was first directed to an undescribed species
about a year ago, when some eggs of whitefly were being examined by
means of a compound microscope. A delicate net, or reticulation, con-
sisting of five- and six-sided meshes, and which can be easily removed.
was then definitely made out (Fig. 12). Comparison of specimens
from different localities showed that some eggs were always perfectly
smooth (Fig. 13), while others always had this net. Examinations of
the first stage larvae of specimens hatched from the smooth eggs, and
irom the reticulated eggs, brought out distinct differences between them
(Figs. 14 and 15).
Fig. 16 shows an older first stage larva of the reticulated egg type.
with a delicate waxy fringe about the margin. This fringe varies with
the age of the larvae, being absent in the very young, and about as
broad, when fully developed, as the lateral bristles are long. The larvae
of the fourth stage (Figs. 17 and 18) and the pupa also show distinct
differences. Differences between the second and third stage larvae of
the two species have not been made out. The empty pupa cases (Fig.
11) of the species with smooth eggs (Aleyrodes citri) are firmer and







Bulletin 97 69

remain expanded, with the T-shaped slit through which the adult
emerged generally wide open; while the empty pupa cases of the
species with reticulated eggs (Aleyrodes nubifera) collapse when the
adults have emerged. and the edges of the T-shaped slit become more
or less folded inwards.


'I


Fig. 14. First stage larva of Aleyrodes Fig. 15. First stage larva of Aley-
nubifera before development of the rodes citri. Enlarged about 100
waxy fringe. Enlarged about 100 times.
times.
The adults of Aleyrodes citri have immaculate wings, while those
of Aleyrodes nubifera have a smoky-colored area near the end of the
wing, easily visible in the living insect with the aid of a lens.


Fig. 16. First stage larva of Aley-
rodes nubifera, with waxy fringe.
.Enlarged about 1 0 times.


Fig. 17. Fourth stage larva of Aleyrodes citri.
Photographed by transmitted light. Enlarged
4.5 times.


~/ ?






70 Florida Agricultural Experiment Station

The distinctive characters of the eggs and first stage larva can
only be satisfactorily seen by the use of a compound microscope; the
remaining characters can be observed with a good hand magnifier. The
following characters can be made out without the use of any magnifier.
The eggs and empty egg-shells of Aleyrodes citri generally appear like
a whitish dust on the leaves, and the tendency is for them to be collected
near the mid-rib (Figs. 1 and 9), except when the eggs are very
numerous on the leaves.
The eggs of Aley-
rodes nubif era (the
cloudy-winged whitefly)
generally have the ap-
pearance of dark or
black dust particles, and
the tendency is for them
to be distributed away
from the mid-rib and to-
wards the margin of the
leaf (Fig. 19).
Aleyro'des nubifera
is at present known to
occur at the following
places: Bartow, Bay-
view, Clearwater, Gen-
eva, Largo, Maitland,
Mims, Orlando, Ozona,
Riverview, Sutherland,
Titusville and Winter
Park. Until the pres-
ent time, Ale yrodes
zubifera has been ob-
served only upon citrus
trees, and both species
Fig. 18. Fourth stage larva of Aleyrodes nubifera. may occur together in
Photographed by transmitted light. Enlarged the same tree, as at Bar-
/ aboutu times.
times, tow, Largo, Maitland,
Orlando, Ozona, and Winter Park. That the yellow Aschersonia ap-
pears to thrive only on Aleyrodes nubifera, anl that the white-fringe
fungus has been observed to be especially effective against this species
of whitefly, were referred to in the accounts of these fungi.

REFERENCES.
1. Berger, E. W.-Whitefly Conditions in 1906. Fla. Exp. Sta.
Bul. 88, 1907.
2. Fawcett, H. S.-Fungi Parasitic upon Aleyrodes Citri. University
of Florida, Special Studies, No. 1, 1908.
3. Gossard. H. A.-Whitefly. Fla. Exp. Sta. Bul. 67, 1903.







Bulletin 97 71

4. Morgan, H. A.-The Orange and Other Citrus Fruits. La. Exp.
Sta. Special Bulletin. 1893.
5. Morrill, A. W.-Fumigation for the Citrus Whitefly. U. S. Dept.
of Agr., Bur. of Entomology, Bul. 76, 1908.
6. Rolfs. P. H., and Fawcett, H. S.-Fungus Diseases of Scale
Insects and Whitefly. Fla. Exp. Sta. Bul. 94, 1908.
7. Webber, H. J.-Sooty Mold of the Orange. U. S. Dept. of Agr.,
Div. of Veg. Physiol. and Path., Bul. 13, 1897.


Fig. 19. Eggs of whitefly (Aleyrodes nubifera), showing distribution
on leaf. x 2.




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