Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 250
Title: Some major celery insects in Florida
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 Material Information
Title: Some major celery insects in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 22 p. : ill., charts, map ; 23 cm.
Language: English
Creator: Ball, E. D ( Elmer Darwin ), 1870-1943
Boyden, B. L ( Boyd Lester ), b. 1885
Stone, W. E ( William Ernest ), b. 1895
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1932
Subject: Celery -- Diseases and pests -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by E.D. Ball, B.L. Boyden, W.E. Stone.
General Note: Cover title.
General Note: "In cooperation with Bureau of Entomology, United States Department of Agriculture, and State Plant Board of Florida"--T.p.
 Record Information
Bibliographic ID: UF00026444
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924109
oclc - 18204699
notis - AEN4714

Full Text


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

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida

Bulletin 250

June, 1932

Wilmon Newell, Director
In Cooperation with Bureau of Entomology, United States Department of
Agriculture, and State Plant Board of Florida.




Formerly Associate Entomologist, Florida State Plant Board and
Florida Agricultural Experiment Station.

Formerly Associate Entomologist, U. S. Bureau of Entomology.

Associate Entomologist, U. S. Bureau of Entomology.

The Celery Leaf-Tier ............................ 3
The Celery Looper ............................. ... 17
Cutworms ................................ ........ 17
Semitropical Army Worm ......................... 18
Red Spider ...................................... 19

Bulletins will be sent free upon application to the

John J. Tigert, M.A., LL.D., President of the
Wilmon Newell, D.Sc., Director
H. Harold Hume, M.S., Asat. Dir., Research
Sam T. Fleming, A.B., Asst.Dir., Administration
J. Francis Cooper, M.S.A., Editor
R. M. Fulghum, B.S.A., Assistant Editor
Ida Keeling Cresap, Librarian
Ruby Newhall, Secretary
K, H. Graham, Business Manager
Rachel McQuarrie, Accountant


W. E. Stokes, M.S., Agronomist
W. A. Leukel, Ph.D., Associate
G. E. Ritchey, M.S.A., Assistant*
Fred H. Hull, M.S., Assistant
J. D. Warner, M.S., Assistant
John P. Camp, M.S., Assistant

A. L. Shealy, D.V.M., Veterinarian in Charge
E. F. Thomas, D.V.M., Assistant Veterinarian
W. W. Henley, B.S.A., Assistant Veterinarian
R. B. Becker, Ph.D., Associate in Dairy Inves-
W. M. Neal, Ph.D., Asst. in Animal Nutrition
P. T. Dix Arnold, B.S.A., Assistant in Dairy In-

R. W. Ruprecht, Ph.D., Chemist
R. M. Barnette, Ph.D., Associate
C. E. Bell, M.S., Assistant
J. M. Coleman, B.S., Assistant
H. W. Winsor, B.S.A., Assistant
H. W. Jones, M.S., Assistant

C. V. Noble, Ph.D., Agricultural Economist
Bruce McKinley, A.B., B.S.A., Associate
M. A. Brooker, Ph.D., Associate
Zach Savage, M.S.A., Assistant

Ouida Davis Abbott, Ph.D., Head
L. W. Gaddum, Ph.D., Biochemist
C. F. Ahmann, Ph.D., Physiologist

J. R. Watson, A.M., Entomologist
A. N. Tissot, Ph.D., Assistant
H. E. Bratley, M.S.A., Assistant
E. F. Grossman, M.A., Asso., Cotton Insects
P. W. Calhoun, Assistant, Cotton Insects

A. F. Camp, Ph.D., Horticulturist
Harold Mowry, B.S.A., Associate
M. R. Ensign, M.S., Associate
A. L. Stahl, Ph.D.. Assistant
G. H. Blackmon, M.S.A., Pecan Culturist
C. B. Van Cleef, M.S.A., Greenhouse Foreman

W. B. Tisdale, Ph.D., Plant Pathologist
George F. Weber, Ph.D.. Associate
R. K. Voorhees, M.S., Assistant
Erdman West, M.S., Mycologist

*In cooperation with U.S.D.A.

P. K. Yonge, Chairman, Pensacola
A. H. Blanding, Bartow
Raymer F. Maguire, Orlando
Frank J. Wideman, West Palm Beach
Geo. H. Baldwin, Jacksonville
J. T. Diamond, Secretary, Tallahassee


L. O. Gratz, Ph.D., Associate Plant Pathologist
in Charge.
R. R. Kincaid, M.S., Asst. Plant Pathologist
W. A. Carver, Ph.D., Asso. Cotton Specialist
R. M. Crown, B.S.A., Asst. Agronomist, Cotton
Jesse Reeves, Farm Superintendent

John H. Jefferies, Superintendent
Geo. D. Ruehle, Ph.D., Asst. Plant Pathologist
W. A. Kuntz, A.M., Asst. Plant Pathologist
B. R. Fudge, Ph.D., Assistant Chemist
W. L. Thompson, B.S., Assistant Entomologist

R. V. Allison, Ph.D., Soils Specialist in Charge
R. W. Kidder, B.S., Farm Foreman
R. N. Lobdell, M.S., Associate Entomologist
F. D. Stevens, B.S., Sugarcane Agronomist
H. H. Wedgeworth, M.S., Asso. Plant Path.
B. A. Bourne, M.S., Associate Sugarcane Physi-
J. R. Neller, Ph.D., Associate Biochemist
A. Daane, Ph.D., Associate Agronomist
M. R. Bedsole, M.S.A., Assistant Chemist

H. S. Wolfe, Ph.D., Asso. Horticulturist in Chg.
Stacy 0. Hawkins, M.A., Assistant Plant


M. N. Walker, Ph.D., Asso. Plant Pathologist
W. B. Shippy, Ph.D., Asst. Plant Pathologist
K. W. Loucks, M.S., Asst. Plant Pathologist
C. C. Goff, M.S.. Assistant Entomologist
J. W. Wilson, Ph.D., Assistant Entomologist
Plant City
A. N. Brooks, Ph.D., Asso. Plant Pathologist
F. E. Nolen, M.S.A., Lab. Asst. in Plant Path.
A. S. Rhoads, Ph.D., Asso. Plant Pathologist
A. H. Eddins, Ph.D., Asso. Plant Pathologist
West Palm Beach
D. A. Sanders, D.V.M., Associate Veterinarian
Fred W. Walker, Assistant Entomologist
David G. Kelbert. Asst. Plant Pathologist


A complete enumeration of the insects that are occasionally
injurious to celery in the fields would include a score or more, but
for practical purposes the discussion may be limited to five forms:
Celery leaf-tier*, celery looper**, cutworms***, semitropical
army wormt, and red spidertt. (This latter pest is not, strictly
speaking, an insect.)
Cutworms are easily recognized by their greasy and thickset
bodies, as well as by their habit of feeding at the base of or in the
heart of the plant. The semitropical army worm in its younger
larval stage is very variable in color but almost always can be
distinguished by a definite hump with shining black markings
situated on the upper side and about one-third of the way back
from the head. As these larvae increase in size they take on
definite yellow stripes. These larvae usually appear on the small
plants in the fall and rapidly destroy them. The celery leaf-tier
and the celery looper are both inconspicuous green larvae that
appear later in the season. The celery looper is the larger and of
a definite green color. It feeds very largely on the outer and
upper green leaves and has a habit of dropping to the ground
when disturbed. It can always be distinguished by its looping
method of travel.

The first carload of celery was shipped from the Sanford area
in 1899 and the industry developed rather slowly but steadily until
1920, at which time 2,000 cars were shipped. Since 1920 it has
rapidly increased to a maximum of about 6,000 cars per year.
During the greater part of this time insect pests were scarcely a
factor in the production of the crop.
Celery leaf-tier larvae had been observed but had not been of
economic importance until the season of 1922-23, when they ap-
peared in large numbers and did considerable damage. In 1923-
24 they were still injurious but not as much so as in the previous
year. In 1924-25 they invaded the fields in alarming numbers,
causing considerable damage. As a result of the three successive
*Phlyctaenia rubigalis Guenee.
**Autographa falcifera Kirby.
***Noctuidae, several species.
fXylomyges eridania Cramer.
ttTetranychus telarius Linn.

Florida Agricultural Experiment Station

seasons' damage, the celery industry was in a demoralized condi-
tion and the future looked doubtful. During 1924-25 several
forms of arsenic were used to destroy the larvae, with dis-
astrous results, as the great amount of arsenical residue on the
celery rendered it unsalable. Expensive washing equipment
afforded partial relief but the whole situation was unsatisfactory.
At this time help was sought and investigations were started co-
operatively by the Florida State Plant Board, the Florida Agricul-
tural Experiment Station and the Bureau of Entomology of the
United States Department of Agriculture. Since that time five
more celery seasons have passed, three in which no damage has
occurred, and two, the seasons of 1926-27 and 1928-29, in which
the damage would have been excessive if control measures had
not been almost universally applied.
The development of efficient control methods meets the im-
mediate need of the grower but an understanding of the factors
that brought about the ruinous outbreak of this pest may easily be
of more value in determining whether such outbreaks are to be
expected in the future or whether the industry may look forward
to comparative immunity from this pest, except as the result of
the culmination of climatic cycles. To test this latter possibility,
an intensive study was made of the factors that contribute toward
the normal natural control of this pest.

The mean temperature of each season from the beginning of
these outbreaks to the present time has been plotted in Fig. 1 A
and B, in which the heavy black lines represent the normal tem-
perature. In the years during which the celery leaf-tier caused
damage (Fig. 1 A) the mean temperature of the four vital months
of the crop season, December to March, is shown to be above
normal with the exception of December of the season 1928-29 and
January and March of the season of 1926-27. The high tempera-
tures of the other months of the seasons entirely offset any in-
hibiting effect low temperatures of the shorter periods of cold
weather might have had. In the years (Fig. 1 B) when the tem-
perature of the four vital months was above the normal mean
only in December and January of the season of 1923-24 and Janu-
ary and February of the season 1929-30 and only slightly above
in February and March of the season of 1927-28, there was only
one case of damage and it was not severe. The abnormally high
temperature during December, 1923, enabled the celery leaf-tier

Bulletin 250, Some Major Celery Insects in Florida

F Ou. S. 0. O. n J. F. TMr. Op. q.u J. S. 0. O D. .
90r ----- -- -------- 43

FIG. 1.-Mean monthly temperatures of seasons with varying amounts of
injury from the celery leaf-tier. A (above), Warm years in which severe
damage occurred. B (below), Cold years, in three of which no damage
occurred; there was slight damage in the fourth.

Florida Agricultural Experiment Station

to develop at a rate much higher than the normal and some injury
resulted in the early celery. However, the colder temperatures of
the succeeding months took care of the situation. The cold tem-
peratures during February and March, the two most critical
months in determining the severity of infestation, may easily be
seen. Taking this as a guide, the mean temperatures of Decem-
ber, January, February and March of each year since 1891 has
been averaged and plotted in Fig. 2. It will be seen from this
diagram that the winter temperatures beginning with 1891 were
almost steadily falling from that time until 1902, and that from
1902 until the present time (1929-30) they have been slowly but
steadily rising, culminating in five of the eight warmest winters
in the last 30 years. These were the five winters in which the
celery leaf-tier damage was excessive.
During all of the generally cold winters from 1895 to 1910 no
celery leaf-tier damage was known, and even in the three recent
winters, 1925-26, 1927-28 and 1929-30, in which the mean tem-
perature was close to the normal, the celery leaf-tier caused no
injury, indicating very definitely that a high winter temperature




92 4 6 8 00 a 4 6 8 )O 2 4 6
P1 1 1 1

8 20 2 4 6 8 30

1- 1AI

4e ery Ll/m ens \1
_- _-_- '

Winter ^e erapeo






FIG. 2.-The mean winter temperatures (December-March) of Florida,
1891 to 1930. Celery shipments and leaf-tier injury for the later years are


E----T7 F I I I

Bulletin 250, Some Major Celery Insects in Florida

is at least one of the essential factors in the development of celery
leaf-tier damage. The older celery growers tell of two periods
previous to the recent outbreak in which the celery leaf-tier
"worms" became numerous enough to pile up under the conveyor
belts. These two periods (1904 and 1907) are plotted beneath the
temperature scale and it will be noted (Fig. 2) that they occurred
when one mild winter followed another, thus indicating that it
takes two warm winters in succession to bring the celery leaf-tier
up to sufficient numbers to begin to be injurious, then after that
succeeding warm winters will be injurious ones. The most recent
outbreak also was preceded by two warm winters in which no in-
jury occurred. It seems probable, therefore, that after a series
of cold winters in which the celery leaf-tier is reduced to a mini-
mum at least two warm winters in succession are required before
the pest reaches the injurious stage, then any succeeding warm
winters will show injury. The writers have obtained the records

1 Scale in' Miles
I Z 3 4 N Legend

*^ ~- .-Homtflock
S ( open) Pine wPoods


'0 W z

0 "

.near Lake Monroe).
Q 0

Florida Agricultural Experiment Station

of winter temperatures in Florida from 1739 to date, with the ex-
ception of 60 years between 1760 and 1820. This gives 130 years'
record of winter temperatures and during this period there were
only six cycles of warm winters comparable to the present cycle.
From a study of records it is evident that the cycle of warm
winters just experienced is not a normal condition and with its
disappearance will probably go the major danger from the celery
The distribution of celery plantings in the Sanford area is
shown in Fig. 3. From this map it will be observed that there is a
solid block to the southeast of the city, a small solid block to the
west, and a still smaller area in the Lake Monroe region, with
scattered plantings around the margins of Lake Jessup, includ-
ing those at Oviedo.
In the study of the distribution of the celery leaf-tier injury
it was soon discovered that the area of worst infestation occurred
in a strip only a mile or two wide extending obliquely northwest-
southeast from the widest place in Lake Monroe towards Lake
Jessup and that a secondary area of slightly less infestation
occurred in that area on the west side still within the influence
of the winds blowing across Lake Monroe from the northwest,
while as one moved westward towards the Lake Monroe railway
station the injury became less and less until it was of no com-
mercial importance beyond the tempering effect of the lake. The
solid block of fields to the south of Lake Monroe station has never
experienced serious injury. In making these observations it was
also noted that the injury of the celery leaf-tier was almost in-
versely proportional to the injury from frost in the different
regions, again suggesting that it was the warming influence of
Lake Monroe on the northwest winds that made conditions more
favorable for the development of the celery leaf-tier. In studying
the winter temperatures it was found that a variation of only 2
degrees in the mean winter temperature of a season would make
all the difference between a serious outbreak and no commercial
injury. Recording thermometers were used on the west side be-
yond the area of commercial damage by the celery leaf-tier and
another set in the strip on the east side where injury was at the
maximum (Fig. 3 B and C). These thermometers showed an
almost constant difference in the average minimum temperatures
during the winter period of approximately 2 degrees (Fig. 4),

Bulletin 250, Some Major Celery Insects in Florida

again indicating the close response of this insect to variations in
winter temperature.

F'. Oct. fov. Dec. Jan. Feb. mar. Qr. mau

\ 8

80 --We .-----------
____ ^ ---- A ^ ^ ---- -^ --- -24

70 -- ---- _- ^-^

0------- es

FIG. 4.-Average maxima and minima (temperatures) of the west side
(Station B) and the east side (Station C) of the Sanford celery area,
plotted by 10-day periods.

Temperature is always a very important factor in the celery
leaf-tier's development but there are two other factors that are
almost equally as important in controlling the celery leaf-tier in
abnormal winter seasons, namely, egg parasites and birds. Tem-
peratures may be predicted in advance in certain cases but they
cannot be controlled, while on the other hand conditions favorable
to the activity of the other two factors are largely within the
control of the growers. It is therefore important that the condi-
tions which favor their operation be understood.

All insects have parasites, predators or diseases that tend to
prevent their rapid multiplication and the celery leaf-tier is no
exception. In the Sanford region it has three parasites, as well
as predators and diseases, that help to keep it in check. By far
the most important of these and in many cases the most import-
ant single factor in its control is a tiny black wasp (Trichogram-
ma minutum Riley) that lays its eggs in the eggs of the celery leaf-
tier and its larvae destroy them. This wasp is not active during
the cold weather of the normal winter period, as it goes into hiber-
nation for several months. It becomes active again a short time

Florida Agricultural Experiment Station

before the celery leaf-tier disappears in the spring. It then breeds
all summer on various other species of leaf-tiers that live on the
careless weeds (Amaranthus spp.) in the fields and usually be-
comes abundant in the fall at about the time the fields are being
plowed up and the careless weeds destroyed. At this time as
high as 160 little wasps have been hatched out of 100 eggs of re-
lated leaf-tiers on the careless weeds.

Seg. Oct. ilo,. Dec. Jan. Feb. Iar. 0pr. maL. Jun. Jul. Oug. Sep.
00 -

50- ----- -..-.- '

Egq Par.
FIG. 5.-The balance of nature The relative importance and period of
activity of the various factors concerned in the normal natural control of
the celery leaf-tier.
Infestation during normal year.
........... Infestation during abnormal year when balance of nature
is disturbed.
Width and length of black markings show relative importance of factors.
Cross-hatching shows when high temperatures become operative in
inhibiting population of celery leaf-tier.

These little wasps are therefore swarming in early October at
the time the celery leaf-tier normally appears in the fall and, with
their other hosts gone, they are immediately attracted to the
celery leaf-tier eggs and destroy them nearly as fast as they are
laid. This good work is kept up until the temperature falls to a
point where they cease to be active, as shown in Fig. 5. As the
temperature continues to fall it materially slows down the activity
of the celery leaf-tier and this continues throughout the winter
period. As the temperatures increase in the spring, however, the
celery leaf-tier becomes more active and would become seriously
injurious if it were not for the third factor, birds.

Bulletin 250, Some Major Celery Insects in Florida

As the migratory birds come through in the spring of the year
and the birds that have been wintering in Florida find the food in
the woods becoming scarce they enter the celery fields and com-
mence to feed on the larvae, pupae and moths of the celery looper
and the celery leaf-tier.
The first bird to appear in numbers is usually the little palm
warbler. These birds perch in the tops of the celery or run up
and down between the rows picking off the larvae and pupae.
Oftentimes they will be seen perching in numbers on the crates
back of a harvesting crew and snapping up every moth that flies
out of the celery.
A little later the swallows appear. They usually spend their
time over the swamps picking up the gnats and mosquitoes, but
as soon as the sprayer or duster appears in the celery fields and
begins to disturb the moths the swallows appear and commence
to snap them up. With the beginning of pyrethrum dusting the
swallows become more important. The pyrethrum is apparently
disagreeable to the moths and they continually dart up into the
air in short flights, only to drop back into the celery again. This
is continued until they finally escape from the dusted area. The
swallows, following the dusters and skimming over the celery
after it has been dusted, pick up many moths that appear above
the surface of the celery. When conditions are favorable the
swallows continue this work for a day or two, or until the moths
are practically eliminated from the field.
Later in the season, after the warblers have gone north and
most of the swallows have disappeared, the mocking birds,
meadowlarks, grackles and blackbirds that are nesting in the
region commence to forage in the celery for the larvae with which
to feed their young. A constant stream of these birds may be
seen going back and forth, flying in an air line from the celery
field to their nests, their bills overflowing with the larvae of the
celery leaf-tier.
In a normal season the birds are plentiful enough to keep the
celery leaf-tier entirely under control in the isolated fields and
those adjoining woodlands. In the solidly planted areas where
there is little shrubbery to afford the birds protection they appear
in smaller numbers and if the infestation is very great there will
not be birds enough to take care of it. Much could be done to en-
courage the birds by the planting of small, shrubby trees like the
haw or the wild plum along the ditch banks in the solidly planted

Florida Agricultural Experiment Station

areas. It might even be possible to set aside small strips a mile
or so apart as bird refuges.

In an average season the celery leaf-tier in the Sanford area
diminishes in population in late May or early June and does not
build up again until about the 10th of October, when fresh moths
make their appearance in the earliest planted seedbeds. The
normal temperature at the time of the apparent disappearance is
between 750 and 770F.* They appear in the fall following the
first sharp drop in temperature after the mean temperature of
the season has fallen to 77' or below. Sharp drops in temperature
at this time almost always follow rainstorms, so that the celery
leaf-tier may be expected to appear as soon as the mean tempera-
ture has fallen to 77' or below and there occurs a rain followed
by a sharp drop in temperature. In an exceptionally hot and dry
fall the moths may not appear until November. In an equally hot
spring they may disappear early in May. One cool September a
part of them came out following a storm and drop in temperature
on the 10th but due to parasites and predators none of these
survived to produce progeny.


The eggs of the celery leaf-tier (Fig. 6 A) are very small, almost
transparent, iridescent and scale-like. They may be deposited in
groups of from 1 to 15 on the under sides of the leaves of the
plant slightly overlapping each other. The eggs are very difficult
to locate in the field and are rarely seen by the growers.

When the larva or worm first emerges from the egg it is
whitish in color with a black head, which color it retains until the
first molt. As it feeds the larva becomes light green in color with a
black head and later develops a pair of longitudinal white stripes
on the back (Fig. 6 B). The mature larva is about three-quarters
of an inch long.

*Since the manuscript for this paper was prepared Dr. Ralph L. Miller
has announced that the celery leaf-tier continues to breed, although in
greatly reduced numbers, throughout the summer months on a number of
native and ornamental plants, including Spanish needle, ragweed, fleabane,
dog fennel, chrysanthemum and calendula (Florida Entomologist, Vol. XV,
No. 2. August, 1931).

Bulletin 250, Some Major Celery Insects in Florida



FIG. 6.-The celery leaf-tier. A, eggs; B, mature larva; C, pupae; D,
adult. A, highly magnified; others magnified from 2 to 3 times. (Courtesy
D. G. Kelbert.)
The mature larva makes a cell among the leaves within which
it transforms into a brown pupa measuring about three-eighths
of an inch in length. As the pupa is inactive and well hidden it is
rarely seen unless the cell is broken open, as shown in Fig. 6 C.

Florida Agricultural Experiment Station

The adult leaf-tier is a small brown moth, less than one-half
inch long, with slight traces of serrated lines on the wings, giv-
ing a somewhat mottled appearance. The wings, when at rest,
form a triangle (Fig. 6 D). The two most distinguishing features
are the brush-like palpi in the shape of a snout and two rows of
small black spots on the under side of the cream colored abdomen.

The planted celery is not large enough to furnish shelter for
the moths that appear by the middle of October, so they seek
shelter in the older seedbeds. Many of the progeny, both eggs
and larvae, of these early moths will be destroyed by the para-
sites. Moths coming out later, after the temperature falls and the


-\---_Z --7"-- ^
O /
70- -F2}

\ _- _' "-

FIG. 7.-The normal life history of the celery leaf-tier in the Sanford area.
The broken line represents normal temperature. The four heavy lines repre-
sent the time of appearance and relative numbers of the generations during
the cooler half of a normal year. The arrow head on the line of the first
generation shows where the moths which really comprise the bulk of the
first generation appear, as the eggs of the moths which appear with the
initial drop of temperature in the fall are practically all parasitised.

parasites have been checked, usually find favorable shelter and
deposit the eggs in the fields of older celery where the plants are
large enough to afford good hiding places. This generation of
larvae appears late in November and throughout December (Fig.
7), and may be found in alarming numbers in a few of the older
fields. Fields set later have fewer larvae and these will be younger
and may not mature by the time the celery is harvested.
The second generation of moths appears in December and Janu-
ary. At about the time the celery harvest gets under way they

Bulletin 250, Some Major Celery Insects in Florida 15

find shelter in the other fields and deposit their eggs in celery
that will be harvested within a month or six weeks. Under the
temperature conditions prevailing at that time it takes nearly two
months for a generation to mature, so that the majority of them
are shaken off in the larval stage when the celery is harvested
and consequently fail to mature. The earlier or older larvae that
succeed in maturing and are thus able to survive, appear as moths
to produce the third generation in February or March. If the
weather is abnormally warm, as it was in 1927, this generation
will do serious damage. If it is more than one degree colder than
normal, as it was in 1926, the injury will hardly be noticeable.
The fourth and last generation appears in April and May and
the injury caused by this generation will depend upon the num-
bers present and the temperature prevailing. Before the end of
May the hot weather causes them to disappear rapidly.
During a normal season four generations of the celery leaf-tier
may be expected. In the cold season of 1925-26, with the late
start in November, only three generations developed. In an ex-
cessively warm season with an early fall start there would be four
complete generations and a few of the earlier moths might lay
eggs for a partial fifth generation. These larvae would, however,
be harvested with the celery and take no part in the perpetuation
of the species.

The length of time required by a celery leaf-tier larva to mature
varies from about 20 days to three months, depending upon the
temperature. The average time in a normal season is about four
weeks. The amount of food that a larva will eat is practically con-
stant, amounting to about two and one-fourth square inches of a
celery leaf, regardless of the time required for its maturity, the
only difference being the rapidity with which the food is con-
sumed. The most striking thing, however, is the relatively small
amount of food consumed by a larva in the first two weeks of its
life as compared with that consumed in the last four or five days,
as shown in Fig. 8.
A study of this chart, in connection with the fact that the
length of time the larva is feeding is dependent upon tempera-
ture, will explain a number of occurrences that would otherwise
be puzzling. A fairly mature celery crop might carry 40 or 50
larvae to the stalk without any damage resulting, if it was har-

16 Florida Agricultural Experiment Station

vested the first two or three weeks of their life. On the other
hand, if this celery, which at the time was showing no damage,
should be boarded about the third week of the larval growth it
might easily happen that when the boards were removed 10 days
later nothing would be found under the tough green leaves at the
top except the bare stalks enclosing a mass of frass.


L^.Z 5 ---------f


.6 5

)VI 24 3d y y5 Weete
FIG. 8.-The relative feeding capacity of a celery leaf-tier larva at
different ages.

In all economic control of injurious insects the factors of
natural control, such as those shown in Fig. 5, should be kept con-
stantly in mind and nothing done, if it can be avoided, which will
seriously disturb nature's balance. The destruction of all the
careless weeds in a region two or three weeks in advance of the
appearance of the celery leaf-tiers might have a very disastrous
effect on the egg parasites and practically eliminate them at just
the period when they should be the most effective.
Birds should be encouraged to inhabit the territory surround-
ing celery fields. It has been observed that the swallows appear
in the celery fields only during a limited period of the day. Pyr-
ethrum dusting should be so adjusted that it will be done not only
under favorable conditions for its efficiency but also under condi-
tions in which the swallows present can work.
A full discussion of control of the celery leaf-tier, particularly
artificial control, will be found in Bulletin 251 of the Florida Ex-
periment Station.

Bulletin 250, Some Major Celery Insects in Florida

The celery looper (or the closely related cabbage looper) is
present on the celery in all sections but rarely in sufficient num-
bers to be injurious. As previously stated, the looper seems to
prefer the green leaves of the outside canopy but occasionally
attacks the inside leaves with serious results. In the Sanford
area the loopers are attacked by a bacterial disease which sweeps
over the fields at intervals and frequently almost elminates these
larvae. This bacterial disease does not attack the eggs or the
moths and the fields are soon reinfested.
In the Manatee and Sarasota districts, where the celery leaf-
tier is very rare, occasional outbreaks of the looper become seri-
ous enough to warrant remedial measures. These attacks are
often mistaken for outbreaks of the celery leaf-tier. Fortunately,
the same treatment that is used to control the celery leaf-tier will
be equally effective with the loopers.
This insect's habit of dropping to the ground when disturbed
often causes unnecessary alarm, as in the handing of the crates
to the washers large numbers of these loopers will work to the
surface and drop off as the crates are being passed along the con-
veyors, occasionally resulting in a considerable accumulation of
worms during the day. If the celery leaf-tier appeared in the
same numbers under the conveyors it would be indicative of a
rather serious outbreak, but in the case of the loopers those under
the belt may represent the major portion in the area harvested
and are not worthy of consideration.

Cutworms, as a group, are northern in their distribution and
therefore adapted to cool temperatures. They are active during
the entire celery growing season and especially so in the spring
and fall. When a weedy field has been plowed and immediately
prepared for celery planting it will frequently be very heavily
infested by cutworms. As these larvae have been deprived of
food from the time the vegetation was turned under until the
celery is planted they often destroy a considerable percentage of
the celery in the first few weeks and continue to injure the re-
mainder by feeding in the heart. If such fields had been sown
with poison bran mash a day or two before the celery was planted
the major portion of this trouble would have been obviated. A
sowing of poison bran mash at any time the cutworms are dis-

Florida Agricultural Experiment Station

covered doing much damage will destroy the greater number of
them. The bran mash should be distributed in the evening, as the
cutworms are most active and travel around at night.
If cutworms appear in the spring in celery that is more than
half grown an application of the poison bran will be effective, but
care should be taken that it is spread on the ground alongside
the row and not dropped into the heart of the celery.

The use of poisoned bran mash is one of the most efficient
methods of getting rid of certain troublesome insects before they
become injurious to plants. It can be distributed on the celery
fields and will eliminate the cutworms. It should be scattered
around the seedbeds before they are planted.
There are many formulae for the poisoned bran mash and
where any of the growers have a satisfactory method they should
follow it. The following is a standard formula:
Bran ............................................ 25 pounds
Paris green or white arsenic...................... 1 pound
Syrup............................................ 1/ gallon
W ater .............. ............................2 or 3 gallons
Oranges (or cantaloupes) ......................... %1 dozen

The bran and poison should be mixed thoroughly while dry.
(One should take care not to breathe the dust from the mixture.)
The syrup should be added to about two gallons of the water and
then sprinkled on the bran while it is being worked so as to
dampen but not wet it, water being added from time to time until
the whole mass is friable. This bait should be distributed in the
dusk of the evening. The oranges or cantaloupes should be
chopped up fine or grated, rind, pulp and all.

As its name implies, this insect is an inhabitant of the more
tropical regions and goes into hibernation during the winter
period in Florida. Its damage to the celery crop usually occurs in
the fall on the early planted celery. In regions where this insect
is particularly destructive a very careful watch should be kept,
because within a very few days after the injury is noticed the
entire crop may be destroyed, unless remedial measures are
instantly applied.
These little hump-shouldered larvae, ranging all the way from
black to pale yellow with black spots on the humps, spread all

Bulletin 250, Some Major Celery Insects in Florida

over the small celery and devour it rapidly. A spraying of paris
green will usually serve to control it, and as the temperatures fall
the danger decreases.
Red spider is a serious pest only in dry seasons. After a long
dry period occurring at any time during the celery growing
season, damage may be expected unless especial attention has
been given to its control.
In the ordinary season the addition of one-half gallon of lime-
sulphur to 100 gallons of bordeaux mixture will keep this pest
under control, but in a time of drought this amount must be
materially increased. In one of the worst outbreaks it was found
that those who were controlling the red spider were using a gallon
and a half of lime-sulphur, in many cases even more, to 100
gallons of spray mixture. Ordinarily this would be considered
dangerous from the standpoint of burning, but by making the
application after the heat of the day is over no damage was ex-
perienced from even the larger amounts.

The red spider appears first in little patches, oftentimes on a
single plant, or two or three plants in a row. It spreads along a
row rather rapidly but does not spread from row to row until the
infestation is serious. As this local infestation develops the
celery leaves turn white. If close watch is kept and these local

FIG. 9.-Strip of celery (foreground) abandoned on account of red
spider damage. Note the whitened foliage.

Florida Agricultural Experiment Station

infestations discovered, a heavy dusting of a mixture of one-
fourth lime and three-fourths sulphur will often stop them at
this point and prevent a general infestation of the fields. If, how-
ever, they are allowed to develop, the injury gradually spreads
down the row and across to adjacent rows and the white patches
begin to appear in the fields.
Figure 9 shows two rows of celery in the foreground badly
infested by red spider. By the time the infestation reaches this
stage the red spiders are climbing up to the top of the tallest
leaves by the thousands and forming bright red balls. At this
time they spin silken threads that float away on the breeze. Figure
10 shows these masses of red spiders and their silken webs.
If the breeze is strong enough the immature red spiders are
lifted by their silken thread and distributed over the field. If the
breeze is not strong enough to lift them, the threads float across
to other rows of celery and the red spiders use these threads as a
bridge and travel over them by the thousands to spread the in-
It is therefore doubly important that no heavily infested spots
of this kind be allowed to remain anywhere in the celery area, as
a single spot may cause an infestation over a wide area in the
direction of the prevailing wind. Even if the celery is ruined, such

FIG. 10.-Tips of individual celery leaves showing the balling up of red
spiders previous to dispersal and the webs they spin at this time.

Bulletin 250, Some Major Celery Insects in Florida

spots should be immediately treated with heavy applications of
the powdered lime and sulphur dust.
Red spider does much more damage in reducing tonnage and
quality in this area than is generally realized and more attention
should be paid to its control, especially in watching for and dust-
ing the first injured spots that appear. With the present efficient
dusting equipment available, it is probable that better control
would be obtained in all bad infestations by using a mixture of
one-fourth lime and three-fourths sulphur as a dust.

At the time this work was begun the writers found calcium
arsenate was used almost universally, whether applied as sprays,
dusts or baits. A series of careful tests were made to ascertain
the relative killing efficiency of this poison as compared with
paris green.
Potted plants were thoroughly dusted on both sides of the
leaves with the different poisons. Cages were then placed
over them and a definite number of the larvae of the celery leaf-
tier were introduced. It was found that the larvae in the calcium
arsenate tests continued to feed for four or five days without
showing any apparent injury-in fact, if the larvae were removed
from the poisoned leaves at the end of the fifth day and fed on
unpoisoned foliage from that time on they matured in normal
manner and produced moths. On the other hand, where the leaves
were dusted with paris green it was found that most of the larvae
ceased to feed within one day or two days and they soon died,
even if removed and put on fresh foliage.
This probably partially explains why so much poison was re-
quired to stop the celery leaf-tier infestations and indicates defi-
nitely that paris green is much more efficient in early applications
for either the leaf-tier, cutworms or semitropical army worms.
(Note: Since this was written, pyrethrum dusts have been
found effective against the leaf-tier and not injurious to celery.
Their use is discussed fully in Bulletin 251 of the Florida Experi-
ment Station.)

Damage to celery in the Florida celery areas is chiefly confined
to five different insects: Celery leaf-tier, celery looper, cutworms,
semitropical army worm and red spider. (This last is not, strictly
speaking, an insect.)

Florida Agricultural Experiment Station

A resume of the seasons since celery has been grown commerci-
ally shows that an abnormally warm winter temperature is the
main factor in causing outbreaks of the celery leaf-tier, and tem-
peratures within a local producing area may vary enough during
the winter season to affect materially the celery leaf-tier situa-
In a normal season the egg parasites and birds contribute to the
control of the celery leaf-tier.
There are normally four generations of the celery leaf-tier in
Florida in the celery.
Each celery leaf-tier larva consumes during its development
about two and one-fourth square inches of a celery leaf. The
amount of food remains practically constant regardless of the
time required for maturity.
The celery looper (or the closely related cabbage looper) is
present on the celery in all sections but rarely in sufficient num-
bers to be injurious.
Cutworms are a factor in all celery growing areas. Poisoned
bran mash applied before planting will largely eliminate them.
The semitropical army worm is present mainly in the fall on
small celery and seedbeds. It is not a factor during the main
celery growing season.
Red spider, especially during dry seasons, is a serious pest. It
can be controlled by timely applications of sulphur and lime.

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