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VIRGIN ISLANDS AGRICULTURAL EXPERIMENT STATION,
ST. CROIX, VIRGIN ISLANDS, U. S. A.
BULLETIN No.
3.
Under the sapenision of the
UNITED STATES DEPARTMENT OF AGRIC
INSECT PESTS OF COTTON IN ST. CROIX
AND MEANS OF COMBATING THEM.
BY
CHARLES
E. WILSON, Entomologist.
Issaed May 19, 1923
WASHINGTON:
GOVERNMENT PRINTING OFFICE,
1923.
VIRGIN ISLANDS AGRICULTURAL EXPERIMENT STATION,
ST. CROIX, VIRGIN ISLANDS, U. S. A.
BULLETIN No.
3.
Under the supervision of the
INITED STATES DEPARTMENT OF AGRICULTIRE
INSECT PESTS OF COTTON IN ST. CROIX
AND MEANS OF COMBATING THEM.
BY
CHARLES
E. WILSON, Entomologist.
T
Issued May 19, 1923
WASHINGTON:
GOVERNMENT PRINTING OFFICE,
1923.
VIRGIN ISLANDS AGRICULTURAL EXPERIMENT STATION,
ST. CROIX.
lUnder the supervision of the States Relations Service, United States Department of
Agriculture.]
A.
C. True, Director.
E. W.
Allen,
Chief,
Office
of Experiment
Stations.
Walter
H.
Evans,
Chief,
Division
of
Insular
Stations,
Office of Experiment Stations.
STATION STAFF.
John B. Thompson, Agronomist in Charge.
Charles
E. Wilson, Entomologist.
r
INSECT PESTS OF COTTON IN ST. CROIX AND
MEANS OF COMBATING THEM/
CONTEXTS.
Page,
Introduction
1
Insects attacking leaf and stem, and
methods of combating them
1
Page.
Insects
attackinsT
boll
and
flower,
and methods of combating them__
10
Miscellaneous
notes
20
INTRODUCTION.
'^Mien
the
writer came
to
St.
Croix
in
June.
1919,
the
cotton
industr}' was at its height.
Production per acre had been stimulated
by economic conditions brought about by the AVorld War, cotton lint
having increased in price from 40 cents to Si. 80 and S2 a pound and
the demand for cotton goods being greater than the supply in many
parts
of the
world.
With the
increase
in
area devoted
to
cotton
production, the control of insect pests of cotton became a problem of
economic importance.
The purpose of this bulletin is to describe the life history of some
of the insects thus far known to attack cotton in
St. Croix and to
suggest methods
of combating the more
destructive
species.
The
insects are treated in the order of their importance as regards attack
on the cotton plant, being grouped under two main headings, those
attacking the leaf and the stem and those attacking the boll and the
flower.
INSECTS ATTACKING THE LEAF AND STEM.
CoTTox WoEM
(Alabama
argillacea)
.
The moth of the cotton worm, sometimes called the cotton cater-
pillar, army worm, candle
fly, and chenille,
is
a native of tropical
America,
being found
in South America,
Mexico,
and
the
IVest
Indies.
The adult moth migrates as far north
as Canada, but
it
does not breed outside of the cotton
zone, because, so
far
as
it
is
known, the larvje feed on the cotton plant only.
(Fig.
1.)
The egg.—The egg, which
is about one-fortieth inch in diameter,
is light green or light bluish-green, and can readily be distinguished
from the leaf after one has become accustomed
to seeing
it.
One
or several eggs may be deposited on the underside of the leaf, usually
at the top of the plant, but they are never found in clusters.
The
duration
of the egg state
is from 2 to 4 days.
Low temperature,
1 The writer acknowledges his indebtedness to the experts of the Bureau of Entomology
for
their
courtesy
in
identifying many
of the
insects mentioned
in
this
bulletin.
The
illustrations were supplied by the Bureau of Entomology.
1
2
BULI^ETIX
3, VIRGIN ISLANDS EXPERIMENT STATION.
liowever, retards development, and occasionally the period required
for hatchino- ma}'
l)e from 6 to 10 days.
FtG.
1.—The cotton woi-m
[AUihaiiKi
(ir(/ill<icc<i)
:
Stapes and work.
The
larva.—The
ego-
hatches
into
a
small,
inconspicuous,
pale
yellowish-green worm that feeds for
a time upon the underside of
the
cotton
leaf.
The
color markinos become
pronounced
as
the
IXSECT PESTS OF COTTOX IX
ST.
CROIX.
3
worm grows, and the back
of the
full-grown worm has
a broad
brownish or black stripe with
a central line, yellowish-green stripe.
Similar
yellowish-green
stripes appear on each
side
of
tj^e
black
stripe.
Each segment of the worm
is dotted, four dots being on the
back and four on each
side.
The lateral dots are smaller than the
dorsal
ones.
Color may
vary among
the
ditl'erent
individuals
in
intensit}', but the markings described above are the most constant.
Five molts occur during the 10 or 14 days covering the lar\al stage.
The larva is very voracious and ruins entire crops unless it is checked.
After defoliating the
plant and
the supply of
leaves becomes ex-
hausted, it attacks the squares, bolls, and twigs.
The larva is always
active and travels over the plant by looping—that
is, by bringing
up the hind pro-legs to the true
legs, causing arching of the back
in
a
loop.
When disturbed
it protects
itself by
a
series of
jerks,
often leaping
1
or 2
feet
horizontally.
Its presence
in the cotton
field can soon be detected by
a rather strong odor resembling that
of the four o'clock flower.
The pupa or chrysalis.—The larva transforms into the pupal stage
on the cotton plant, such transformation usually being called " web-
bing up."
The worm pupates in a leaf which
it folds over with a
light
silken web
to form
a
cocoon.
Frequently
the pupa
is
seen
hanging from the plant by
a thread, but in such cases the
leaf in
which
it was spun has been eaten by other caterpillars.
"When
it
is
first formed the pupa
is green, but
it soon changes to dark brown.
The pupal stage lasts from 7 to 10 days.
The
aduJt.—^The moth may
be
brownish-gray,
olive-brown,
or
olive-gray.
It has a wing expanse of about 1| inches.
The upper
surface of the anterior wing bears a distinct black spot at about one-
third the distance from the
anterior to the posterior margins, and
the forewings are marked with
a number of dark,
reddish, wavy,
transverse
lines.
The moths fly
at night and hide during the day.
Egg laying starts a few days after the moths emerge from the chrys-
alis, each female depositing from 300 to 600 eggs.. The moths feed
on nectar obtained from the leaf glands of cotton.
»
CONTROL.
Arsenicals.—Paris green mixed with eight times its weight of air-
slaked lime has given great satisfaction as a control measure at the
experiment station.
After
it has been thoroughh' mixed the poison
should be passed through
a
fine wire-mesh sieve, placed in a
finely
woven cotton
sack, and
slightly shaken
oA'er the
plants.
Yellow
cotton cloth is splendid for this purpose.
Burning of the leaves was
not noticed to occur on plants that had been treated with Paris green
and
air-shiked
lime.
Powdered
lead
arsenate
mixed
with
e(inal
parts of air-slaked lime
is not as efl'ective as Paris green: and Lon-
don purple, owing to
its variable composition, can not be depended
upf)n for dusting purposes.
Xatfrral eneinks.—Two l)irds. tlie gray kingbird {Ti/rannus domi-
nicensis domirucensis)
and
the black
Avitcli
or Judas bird
iCrrjto-
phacfa ani), eat large numbers of the larva^ and adults and are of
great
value
in
controlling
the
cotton worm.
The
jack Spaniard
(Polisfes annularis) and the ground beetle {Calosoma calidum)
also
eat
the
larvae.
Dipterous and hymenopterou.s
parasites, inchuling
Chcdcis rohusfa, as well as ants and lizards, helj) to control this pest.
4
BULLETIN
3, YIEGIN ISLANDS EXPERIMENT STATION.
Blister Mite (Eriophyes gossypii).
The blister mite attacks
all parts of the cotton plant except the
root.
When
thoroughly
infested
the
plant
presents
a
distorted
appearance, being only a mass of warts and nodules which are lined
with a thick growth of fine hairs.
The mites live and develop within
the blisters.
The adult
is a minute 4-legged mite that can be seen
only with
difficulty
without
the
aid
of
a
magnifying
glass.
It
severely injures and in extreme cases kills the cotton plant.
A closed season is the most effective means of keeping the pest in
check. A period of from 2 to 4 weeks
is
sufficient, and
if properly
carried
out, the law should prove beneficial
in the shorter period.
The law in St. Croix compels cotton growers to uproot and burn old
cotton
plants by
a
certain
date
fixed
for each
plantation by
the
Cotton Pest Commission, composed of four cotton growers and the
agronomist
in charge
of
the
agricultural experiment
station.
A
period of three weeks is generally designated during which no cotton
can be planted.
After the expiration of this period the cotton seed is
planted as soon as the weather permits.
The law gives the privilege
of granting different periods for different plantations when no harm
is likely to result by so doing.
This variation in closed seasons can
readily be allowed where a range of hills cuts off one plantation from
another, or where each plantation
is separated by the distance of a
mile or more and the prevailing wind is not in a direction to convey
mites from the old cotton plants.
The fall army worm, or corn earworm, army cutworm, and south-
ern
grassworm,
^^^^^s^
V
y
as
it
is
com-
Fall Aemy Worm {Laphygma frugiperda)
.
50 to 400 on blades of grass growing on low land.
The eggs hatch in
from 2 to 6 days.
(Fig. 3.)
IXSECT PESTS OF COTTOX IX
ST.
CROIX.
5
The larva.—The larva reaches maturity in from 7 to 12 days.
Four
molts occur during this period, the first taking jDlace the first day, the
second in from 1^ to 2 days, the third in from 2 to 4 days, and the
fourth in from 21 to 4
da^^s.
When
first hatched
it feeds upon
its
eggshell and later on grass blades.
The newly hatched worm has a
Avhite body and jet black head, but as
it grows and molts its body be-
comes darker.
^A^ien full grown
Fig.
3.—The
fall
army
worm
hatched
larA-a,
or
woi-m."
enlarged.
Newly
Greatly
it
IS
about
1^
inches
long
and
varies from light -greenish yellow
to almost black. A wavy, yellow-
ish
lin-^
is found on each side of
the body and three narrow stripes
run along the back.
The dorsal
surface
of
each
segment
shows
four black dots, and the front of the head
is marked with a white
inverted A.
The jmpa.—When
it
is full grown the larva enters the
soil to a
depth of from one-half to 2 inches to pupate.
The pupal period lasts
from 10 to 14 days.
(Fig. 4.)
The adult.-—The moth varies greatly in color but usually the fore-
wings range from dark gra}^ to brown mottled with black and white,
and the hind wings have a white, brilliant sheen.
The wing expanse is 1^ to 1| inches.
' The body
is gray.
CONTEOL.
Arsenicals.—The
grass
surrounding
the
cot-
ton
field should be dusted with equal parts of
arsenate of lead and air-slaked lime before the
fall army worm makes
its attack upon
cotton.
Paris green and air-slaked lime should be used
as a control measure after the cotton is attacked.
XatiiraJ enemies.—^^atural enemies attacking
the
fall army worm include the gray kingbird,
black witch, chickens, ground beetle {Calosoma
ealidum)
; hymenopterous insects, including Chaleis rohusta^ Spilo-
chaJcis femorata^ S. vittata. and Enicospilus eoneoJor and a dipterous
parasite
{ExoHsta
pyste).
Ants
and
lizards
also
destroy
large
numbers of the larvae.
-Tlu> fall army
I'upa.
About
natural
size.
CoTTox-iiOLL CuTWOKM
(Prodcnia oniithogaUi and P.
latifascia )
.
The cotton-boll cutworm, or cotton cutworm, is found throughout
the year in
St. Croix, and in great numbers from about July 15 to
October
1.
It attacks the cotton plant soon after the seeds sprout,
and later injures the squares and bolls.
(Fig.
5.)
Cotton-boll cut-
worms were veiy numerous in the summer and fall of 1920 and their
attack resembled that of the fall army worm.
They feed on grasses,
Aveeds, niost of the ^ruck crops, and*^the physic-niit
( Jatrop7ia gos-
si/plifolia), in addition to tlie cotton plant.
Of
the two
species, P.
ornltJiogalU
is
tlie more common
in
St.
Croix.
-Since the
life
history of the two species
is almost
identical, only that of P.
ornitho-
(laUi
is fdven.
6
BULLETIN
3, YIRGIX LSLAXDS EXPERIMENT STATION.
Fig.
5.
Prodenia
oniitJior/aJU.
Dark
form, male above
;
pale form, female
below.
Somewhat
enlarged.
27ie egg.—The egg's are deposited in irregular clusters of from 50
to 200 on the undersides of leaves of a number of kinds of plants.
They arc usually cohered with brownish-gray down from the body
of the female.
They hatch in from 4 to 6 days.
The
larva.—The
larvae vary
greatly
in
color,
but two
distinct
forms, the
liglit and the dark, are found in
St. Croix.
(Fig.
6.)
The dark form ranges from dark
velvety-brown
to
a
rich
greenish-
black, with two rows of triangular
velvety-black spots extending down
its back.
It
is the more commonly
found of the two.
The light form
is similar in appearance, the excep-
tion being that
it
is light velvety-
brown instead of black.
The larvae
complete their development in from
IT to 20 days and enter the soil to
pupate.
They
are
1^
to
If inches
long when full grown.
The
f upa.—The
pupa
is
dark
brow^n and has a smooth, glistening-
surface.
The pupal stage lasts from
14 to 20 days.
The adult.—The adult is a brown-
ish-gray moth having
a wing
ex-
i:>anse of
1^
to
If inches.
The forewings are dark brownish-gray
somewhat blotched with white.
On the outer margin of the
fore-
wing there are five wavy lines which are white, brown, broken yel-
low, chocolate brown dotted with light gray, and light brown broken
by yellowish-white marks, respectively.
The hind
wings are a glistening pearly white and have wavy
light-brown
lines extending inside the outer mar-
gin.
The
body
is
covered
with
brownish-gray
down.
Cotton-boll cutworms are controlled by the use
of Paris green and air-slaked lime, the mixture be-
ing prepared and applied as in the case of the cot-
ton worm.
Natural enemies play an important part
in the
control of this pest.
West Indian Sugak-cane Root Bouer
(Diuprepes
abhreciatus)
.
^
Fig.
6.
Prodenia
The West Indian sugar-cane root borer
is often
p.^ie ''^foim
of
very
destructive
to
cotton plants
about
the time
lan-a;
h,
6aii<.
they commence to flower.
The adult beetles f^ed
on the tender growth of the plant, destroying both leaf and flower
bud.
One
large brood
occurs from the
last
of September
to
the
middle of October, and scattered adults are found every month in
the year feeding on a variety of plants.
I^'SECT PESTS OF COTTOX IX
ST.
CROIX.
7
The egg.—The eggs are oblong, white, and glistening.
They are
deposited on the surface of the leaf, usually of sugar cane or grass,
and
are concealed by the fastening of two
leaves together by
the
female, or within the folds of one
leaf.
The eggs hatch
in from 7
to 10 days.
The
larva.—As soon
as they
are hatched the
larva? drop
to
the
ground and feed on the roots of the plant.
They are white or slightly
yellowish-brown, have
a brown head, and
a curved body which
is
footless.
They require from
8
to 10 months for development, and
feed during this time on the roots of the cotton and other plants.
During March larvse measuring from one-sixth to five-sixths of an
inch were found at the experiment station.
The pujya.—The pupa
is very soft and of yellowish-white
color.
Before pupating, the larva forms an earthen
cell in which
it trans-
forms.
The pupal stage lasts about a month.
The adult.—The adult
is grayish green and has somewhat striated
elytra,
the
stride
usually numbering
four.
An
ochraceous-yellow
stripe occurs on the lateral side of the thorax, posterior to the eye and
along the lower margin of the
elytra.
The dorsal
surface
of the
thorax and
elytra
are coarsely punctate.
The ventral surface and
legs are slate-gray, the beak
is thick, and the antennae are long and
elbowed.
COXTEOL.
The adult beetles can best be controlled by hand picking.
They
do more damage to a cotton crop following cane than
is the
case
when cotton follows cotton.
Large numbers of the adults may be
trapped by the planting of sunflowers among the cotton.
The gray kingbird {Tyrannm dominicensis dominicensis) and the
black. witch
(Crotophaga
ani)
are among
the
important
natural
controls.
Teopical Cutworm {Xylomiges sunia).
The tropical cutworm is seldom present in such numbers as to be
of economic importance.
The egg.—The eggs are pale green and are deposited in clusters
of 200 to 300 on the under surface of the leaves of the castor bean,
cotton, beet, and chard.
They are covered with a light-gray or white
down from the body of the female.
They hatch in four to eight days.
The larva.—The full-grown larvae are from 1^ to 1^ inches long.
The dorsal surface of the larva
is dark gray, marked with velvety-
black
patches.
The
sides
are marked with
a
yellow band.
The
larval period lasts from 12 to 20 days.
The pupa.—Pupation takes place in the soil and lasts from 10 to
12 days.
The pupa is brown, smooth, and glistening.
The adult.—The adult moth has a wing expanse of from 1\ to 1^
inches.
The forewings are grayish-brown and the hind wings are a
glistening pearly white.
CONTROL.
Dusting
cotton -for
the
control
of
the
cotton worm
(Alahama
argillaeeei) will also control the larva? of the tropical cutworm.
The
parasitic fly, Exorlsta py-^te.
is a natural means of control.
8
BULLETIN
3, VIRGIN ISLANDS EXPERIMENT STATION.
Cotton Aphis (Aphis gossypii).
The presence of the cotton aphis, also known as the melon aphis,
plant-louse, and cotton louse, can be detected by the curled and blis-
tered appearance
of the
leaves.
The
insect occurs abundantly on
young
cotton
in
^St.
Croix,
especially when
the
weather
is
dry.
(Fig. 7.)
The nymphs and adults seriously check the growth of the
young plant by sucldng
its juice.
No permanent injury has as yet
been observed, probably because as the insects become abundant their
natural enemies increase in number sufficient to destroy them.
Fig.
7.
Aphis
gossypii:
a, Winged
female;
aa,
enlarged
antennae
of
same;
ah,
dark
female, side view
;
I), young nymph or larva
;
Cj last stage of nymph
;
d, winged female.
All greatly enlarged.
The adult
is green or brownish-green, winged or
wingless, and
soft bodied.
The nymphs, or young aphids, are similar in appear-
ance, except that they are wingless.
Nymphs and adults are found
together in colonies on the underside of the leaf.
They prefer tender
growth and young leaves for
food.
CONTROL.
Measures are not necessary for the control of aphids on
cotton.
They are naturally controlled by two enemies, a parasitic hymenop-
teron
{Lysiphlebiis Jestaceipes)
and
a
predacious
ladybird
beetle
{Cycloneda sanguinea), usually called the "red ladybird."
During
February and March about 93 per cent of the aphid colonies were
parasitized by Lysiphlehiis testaceipes.
Other enemies of the cotton
aphis are the lace-winged fly larvae and the syrphus-fly larvae.
IXSECT PEST? OF COTTOX IX
ST.
CROJX.
9
Cotton Lace-bug
i Coriithuca gossijpii
Tlie common lace-biig rarely causes much damaofe to cotton, but
A'ery seriously injures the
leaves of the castor bean
(Ricinus com-
Tii link).
The eg<]:s of the cotton lace-bug are somewhat flask-shaped and are
deposited within the tissue of the
leaf.
In a few days they hatch
into wingless nymphs, which congregate in colonies Avith the adults
on the underside of the leaf.
Both nymplis and adults feed by insert-
ing their beaks into the tissue and sucking the plant juices from the
leaves.
This causes the leaves to turn yellow and die.
Lace-bu<rs rarely become numerous enouHr on cotton to cause severe
damage.
Red Spider
{Tctninvchus
telarius).
The red spider, or spider mite, is of very slight economic importance
in so far as its attack on cotton is concerned.
It is found on the cotton
plant during extremely dry weather only.
Irs native food plant is a weed (Leonotls
nepe teefolia), locally known as ''hollow
stock."
(Fig.
8.)
It can best be con-
trolled by the destruction of this weed.
Scale
sects
a^td Mealybugs.
Scale insects and mealybugs rarely be-
come numerous on cotton until about the
time the plants are to be destroyed.
The West Indian or white-peach scale
{Aidacaspis
pentagona)
rapidly
in-
creases
in number on old
cotton plants
and soon covers stalks and
st ms.
This
pest can best be controlled by the destruc-
tion of the plants.
The
black-shield
scale
{Saissetia
nigra)
is
commonly
found
on
cotton
from December to April, but can not be
considered
a
serious
pest, because
it
is
controlled
by
a
minute
parasitic
hy-
menopterous
insect
known
as
Zaloph-
thrij- minim.
The
black
scale
{Saissetia
oleoe)
attacks cotton too
late
in the season to
b? of economic importance.
By a rigor-
6us
observance
of
the
cotton-pest
law
this scale can be destroyed.
The hemispherical scale
(•S'. hemispharica) has not been found on
cotton in sufficient numbers to necessitate the use of control measures.
The destructor scale {A^pidiotus destructor) has been found only
on old leaves.
Measures for the cr)ntrol of this scale insect on cotton
are not necessar}'.
The
spotted
mealybug
{Pseudococcus
virgatus)
and
the
long-
tailed mealybug (P. Jongispirnis) are usually found inside the calyx
and
are
controlled
bA'
natural
enemies.
The
red
ladvbird
beetle
Fig. S
The red
spicier. Teirnny-
chus
telarius:
AdulL
female.
Greatly enlarged.
10
BULLETIX
3, VIRGIN ISLANDS EXPEPJxMEXT STATION.
{Cijcloneda sa-ngu'm.ea) and its larvse are among the important natu-
ral enemies.
Lesser Cottox Woem
( Alctia
luridiila)
.
Larviie
of the
lesser
cotton worm
are
generally found with
the
larvae
of
the
cotton worm
{Alabama
argillacea)^ and on
account
of their h3,bits, manner of feeding, and appearance they are usually
mistaken for the
latter.
The larvse of the lesser cotton worm differ
from
the cotton-worm
larvse
in
size and
color, being smaller and
reddish brown.
The pupal stage
is spent
in the
soil.
The
adult
moth
is smaller than the cotton-worm moth, and
is a dull gray or
reddish brown.
CONTROL.
The
lesser cotton worm can be
controlled
at the same time
the
cotton worm is checked by the use of arsenicals.
Spotted Flea-beetle
{Homopliceta
cequinoctialis)
.
The spotted flea-beetle
is usually found feeding on cotton leaves
from February to April, but is never present in such numbers as to
attract attention.
No control measures are required for this species.
Greenhouse Thrips
{HeliotJirips hwmorrhoidalis)
.
Greenhouse thrips have been taken from cotton, but never in suffi-
cient numbers to warrant the use of control measures.
A small brown thrips (probably Frankliniella gossypiiA) has been
taken from young leaves surrounding dead flower buds.
Sick Cricket {Amphiacusta caraihce).
The sick cricket is usually found beneath the calyx.
It is an indis-
criminate feeder, but has not been found in large enough numbers to
necessitate the use of control measures.
This species feeds at night.
Sphinx or Hawk-moths.
• The sphinx or hawk-moth species that have been reared from cot-
ton
are the white-lined sphinx
(Deilephila
lineata), tomato-worm
moth
(Protoparce
rustica), tobacco-worm moth
{P.
sexta),
alope
sphinx {Erinnyis alope)
^ and ello sphinx {E. ello).
The presence of sphinx moths on cotton may be called accidental.
They never occur in such numbers as to require the use of control
measures.
Snowy Tree Cricket
{QJcanthus niveiis).
Few specimens of the snowy tree cricket are found on cotton.
The
female deposits her eggs on the cotton stalk in rows, forming long
scars.
The snowy
tree cricket may be
classed
as
beneficial rather
than as injurious, since both young and adults feed on aphids.
INSECTS ATTACKING BOLLS AND FLOWERS.
Pink Bollworm
{Pectinophora
gossypiello)
.
The pink bollworm is very destructive to both cotton lint and to
cotton seed.
It stains the lint, causes it to be short and kinky, and
IXSECT PESTS OF COTTOX IX
ST.
CROIX.
11
more or less cements the lint and seeds together.
It greatly reduces
the yield of lint and the amount of seed produced.
The seed is also
of light weight and
germinates
poorly.
The pink bollworm
may
be
found
in
one or several locks
of the boll, but on?
worm
seldom
at-
tacks more than one
lock.
(Fig.
9.)
Counts
of
bolls
on
plants taken
at
random
from
the
field
during
Jan-
uary. F e b r u a r
,
March,
a n d
the
early part of April,
1921,
showed
that
from
5
to
25
per
cent
of
the
1921
crop
was
a
loss.
On this account the
old
cotton
plants
were
not
removed
from the fields and
no new crop was planted.
The
bolls on old cotton plants showed
30 per cent infestation on February 11, 1922.
(Fig. 10).
This con-
dition was reported to the Cotton Pest Commission, and within a few
days the removal and destruction of all cotton plants was requested.
Fig.
-The pink boUwoim
( Pcctinophora gossypieUa)
Adult.
Much
enlarged.
Fig. 10.—Exit holes of pink boUworms in cotton
bolls;.
The egg.—The eggs of the l)ollworm are deposited singly near the
points of green bolls in the sutures marking the locks.
A number of
12
BULLETIN
3, VIRGIN ISLANDS EXPERIMENT STATION.
eggs are often found on the same
boll.
They hatch
in from 4 to
12 days.
The larva.—The white or yellowish-white larva bores its way into
the boll almost as soon as
it
is hatched.
After entering the boll
it
feeds upon the seeds, which
it cements together.
Cementing of the
seeds
is a characteristic feature of the work of the pink bollworm.
The
larva becomes
pink as
it develops
within the boll and
measures
one-half
inch
when
fully
grown.
(Fig.
11.)
In
St.
Croix
the
larval
period
usn-
ht conditions apparently pro-
ne.
11.
-The
pink
bollworm
:
Outline
drawing
of
larva,
showing
structure.
Much
enlarged.
Drou<
ally
lasts from 12 to 11 days,
long the period.
The pupa.—Before passing into the pupal state the larvae usually
spend one day in a prepupal stage.
The pupa
is brown or reddish
brown.
The prepupal and pupal period lasts from 9 to 12 days dur-
ing February and March.
The pupal
period
of
three specimens
lasted 22 days in March, 1921.
(Fig.
12.)
The adult.—The adult moth is dark brown or dark grayish brown
and has
a wing expanse
of from two-thirds
to
seven-eighths
of
an
inch.
Ths
forewings
are
somewhat narrow, pointed, and edged with long
brown
fringe.
The
hind
wings
are somewhat
broader,
more
pointed,
and
edged
with
longer
fringe.
They are usually lighter in color than th ^
forewings.
In St. Croix the minimum time required for de-
velopment from the egg to the adult stage has been
28 days, and the maximum time under laboratory
conditions has been 42 days.
CONTROL.
At
the present writing cotton growing
in
St.
Croix has b:en
suspended.
It
is hoped that no
cotton will b? planted for a period of three years
or more,
as a closed season
is the only practical
m6ans of control so far known.
Adult moths of the pink bollworm have been
found
infested with numerous predacious mites
of
the
genus
Pediculoides.
When
these
mites
crawl upon the hands and forearms of the pickers
fig
they
cause
severe
irritation
which
results
in
dermatitis.
12.—The
pink
IwUworm
:
Pupa.
Much
enlarged.
Southern Green
Stink-bug
(Nczara
viridula).
The southern green stink-bug, also known as the stink-bug, bush
bug, green plant-bug, green soldier-bug, green bug of India, pumpkin
bug, green bug of cotton, shield bug, and green shield bug,
is now
found in tropical and neotropical regions
all over the world.
The
IXSECT PESTS OF COTTOX IX
ST.
CROIX.
13
southern green
stink-bug
inserts
its beak
into
cotton
bolls when
feeding and thus introduces the fungus causing internal boll disease.
(Fig. 13.)
The egg.—The
eggs
are
deposited
in compact, hex-
agonal
clusters
on
the u n d e r
surface
of
tomato,
tobacco,
okra, corn, and many
weeds, the individual
eggs being
firmly
glued
together
in
very
regular
rows.
The egg clusters are
Av h i t e
or
creamy-
white when
first
de-
posited and later be-
come broAvnish-pink.
Shortly
before
they
hatch, the eggs pre-
sent
a
reddish
ap-
pearance,
the
color
of the nymphs being
visible
through
the
shell.
The egg clus-
ters contain from 48
to 118
eggs.
Under
laboratory
c o n d i -
tions the eggs hatch
in from four
to
eight days.
(Fig. 14.)
27ie ni/mph.—F\\e molts occur during the nymphal period.
The
nymphs of the
first instar molt in from 2^ to 4 days; those of the
.-econd.
in from
5
to
12
days;
those of the third, in from 2 to 8
days;
those
of
the
fourth,
in
fi-om 5 to 10 days
; and those of
the
fifth, in from
5 to 20 days.
(Fig.
15.)
The most rapid de-
velopment takes place from Sep-
tember to January.
The adult.—The adult is light
green, shield-shaped, aud varies
considerably in size in V)oth male
and
female.
Both
adults
and
nymphs emit a malodorous sub-
stance for protection.
-Southern
green
plant-bug
Adult.
Enlarged
about
4
i ~Sezfira
viridiila
i
diameters.
Fig.
14.—Southern
green
plant-bug
:
Egg-
cluster,
viewed
from
above.
Enlarged
about 6 diameters.
hand
is
the most
satisfactory
gi'een stink-bug on cotton.
CONTROL.
Hand
picldng.—Picking
by
method
of
control
of
the
soutliern
14
BULLETIN
3, VIRGIN ISLANDS EXPERIMENT STATION.
Natural enemies.—A dipterous parasite {Trichopoda pennipes)
is
tlie most important natural control for the
^rreen stink-bug
in
St.
Croix.
Field
collections of Nezara viridula show that the largest
amount of parasitism occurred in Januar}', when 93 per cent of the
Fig.
15.
Nezara
viridnJa: Nymph,
fifth
instav
;
light and
dark
types.
Enlarged
G diameters.
specimens
were
parasitized.
The
smallest
amount
of
parasitism
occurred in July, when field collections showed 12.28 per cent of the
specimens parasitized.
(Fig.
16.)
The black witch and the gray
kingbird eat both nymphs and adults of the southern green stink-bug.
IXSECT PESTS OF COTTOX IX
ST.
CROIX.
15
Cotton Stainer
(Di/sdercus andrra).
Cotton
stainei-s are always abundant on cotton bofe during the
winter and early spring months.
Only one species
is found in
St.
Croix.
The insect
is called the cotton stainer because
it injures the
cotton by staining the lint.
The
€(/(/.—The eggs are laid in clusters on the ground or dropped
into opening cotton bolls.
They are small, yellow, and glistening.
The nymph.—The nymphs are red in color.
The development of
the nym2:)h is gradual.
The adult.—The adult cotton stainer is red, black, and white.
The
head and the thorax are red.
The latter has a white line on the an-
terior and posterior margins.
Just inside this margin there is a black
line.
"When the wings are folded the dorsal surface
is marked with
a large white X.
Between the upper arms of the X the color
is red
or reddish-black, while between the lower arms of the X the color
is
black. A red triangle containing a black spot is found on each wing
cover.
The
lower
surface
is
red
and the legs are black red.
Both nymphs and adults live by
sucking the
juices from the
bolls.
The
staining
of
the
cotton
lint
takes place when the insects
feed.
COXTROL.
Cotton stainers can -best be con-
trolled by picking by hand and by
trapping.
The stainers congregate
in groups on the cotton
bolls and
can be brushed from them into pans
containing a
little water and kero-
sene.
Handfuls
of
cotton
seed,
dropjDed on the ground between rows of cotton,
attract large num-
bers of the stainers.
Boi.LwoRM
(Hcliothis obsoleta).
The
bollworm,
cotton
boUworm,
corn
earworm,
tomato
fruit
worm, and budworm, as
it
is
called,
is found in most of the tem-
perate and
tropical
regions of the world.
(Fig.
IT.)
The
larvae
feed on
a large variety of
plants, but severely
injure
corn, cotton
bolls, tomatoes, and tobacco.
The
efjrj.—The eggs are small, wliite
in color, and are oviposited
on the leaf or fruit of the
liost plant.
Thev hatch in from 2^
to
7
days.
The
larva.—The
larva, upon
liatcliing.
feeds upon
the
eggsliell
and then upon the host plant.
At this time
it has a yellowish-white
body and a black head,
^ix molts occur during the larval period.
The adult larva? vary greatly
in color, ranging from
pale green
to
pinkish, gray green, light and dark brown, grayish black, and almost
black.
The full-grown larva is al^out 1} inches long, and pu})ates in
tlie ground at a depth of from 2 to 4 inches.
(Fig. 18.)
Fig.
— Trichopocia
penuipes.
Adult
fly, three times natural
size.
16
BULLETIN
3, YIEGIN ISLANDS EXPERIMENT STATION.
The 2)upa—The pupa is incased in an earthen cell.
The pupa is a
smooth, shining- bro^Yn in appearance.
The pupal stage lasts from 14
to 18 days.
(Fig.
19.)
2'he adult.—The adult moth has a wing expanse of from 11 to 1%
inches.
The adult ranges in color from pale grayish green to almost
brown.
(Fig.
20.)
Fig.
17.—Cotton
boll
with
full-grown
bollworm
eating
into
tip.
CONTKOL.
Large numbers of the bollworm
larvae
are
killed by the
use
of
Paris green when
it is applied to the cotton plant for the control of
the cotton worm {Alahama argillacea).
The
bollworm
is
parasitized
by
the
following
hymenoptera:
Chalcis Tohusta, C. annulata
(?), Spilochalcis femorata^ S. vittata^
and Enicospilus concoloi\ and by the fly Exorista pyste.
The preda-
IXSECT PESTS OF COTTOX IX
ST.
CROIX.
17
ceoiis ground beetle Calosoma caJuhim eats the larvje when they drop
from the plant to pupate.
The adult moths are caught by the gray
kingbird and the black witch.
Fig.
18.—Three cotton boUworm
larvtE,
seen from
the
side, showing color
types.
Upper
larva,
green
;
middle
larva,
rose
colored
; lower
larva,
dark
brown.
Flower-bud Maggot (Contarinia gossypH).
The flower-bud maggot occasionally attacks cotton flower buds in
St. Croix.
Its presence may be noted by the flaring of the bracts of
a
h
Fig.
10.—Adults of cotton bollworm
:
a. With winjrs spread
:
h,
in
resting position, wings
folded.
Twice natural
size.
the flower buds.
This worm causes the squares to drop, resulting in
a small crop.
The eggs are laid in the young flower buds of cotton.
On hatcliing.
the laiwK feed inside the flower bud. causing the death of the bud.
18
BULLETIX
3, YIRGIX ISLAXDS EXPERIMEXT STATIOX.
The
larvae are yellowish-white
or pinkish
in
color and when
full
grown
are about 2 millimeters
long.
Pupation takes place
in the
soil.
The adult fly is a minute insect, about one-sixteenth of an inch
long.
The face is fuscous, and the eyes are large.
The scutellum
is
yellowish and tlie abdomen greenish-yellow.
The flower-bud maggot has not been found generally distributed
in the cotton fields during the past three years, and control measures
have not been n:eded.
BoLLwoR^t
(Heliothis
virescens).
The bollworm,
also known
as
the
tobacco budwoim,
is
usually
found with the cotton bollworm
{H.
ob^oTeta).
The habits of the
two species are the same.
Only a few larvae have been taken from
cotton bolls in St. Croix, but they have been present in some num-
bers in okra pods and tobacco-se?d pods.
The
life histories of H.
obsoleta and 11. virescens are almost iden-
tical.
The full-grown larvae are usually
yel-
lowish-green and pupate in the soil.
The
adult moth has a wing expanse of 1^
to
1^ inches.
The forewings are olive green
crossed transversely by three lighter col-
ored
lines.
The hind wings may
be
a
shining
white
or
white
with
the
outer
third brown or pink.
CONTROL.
This species
is controlled by the same
method used
to combat
the
cotton
boll-
worm
(Heliothis
oljsoleta).
I'lXK Scavenger Worm
{ Pijroclerces rileiji)
.
The larvae of the pink scavenger worm
or pink cornworm has been found only in diseased bolls or bolls in
which pink bolhvorms {Pectinophora r/ossypielJa) have worked.
It
can not be considered a pest of cotton.
The egg.—The eggs are small, pearly white and shining.
They are
deposited singly or in groups of
3 or 4 between rows of grain, on
ears of corn, and on corn silks.
The larva.—When they are first hatched the larvae have creamy or
yellowish-white bodies and a dark head.
The body soon changes to
pinkish color, but the head remains dark. When they are full grown
the larvae measure about one-third of an inch in length.
The
pu2)a.—The pupa
is a light yellowish-brown and
is smooth
and shining.
The
adult.—The adult moth has
a wing expanse of one-third to
one-half inch.
The forewings are ITimded and mottled with yellow,'
light brown, and black.
About two-thirds of the basal margin has
long fringe.
The hind wings are very narrow and have very long
fringe on the basal portion and shorter fringe on the anterior mar-
FiG.
20.—Pupfp
of
cotton
boll-
worm.
Twice natural size.
IXSECT PESTS OF COTTOX IX
ST.
(^KOIX.
19
gin.
The color of the liind wings is grayish-brown.
The adult inotli
IS very active.
Control measures are not necessary for this species on
cot (on.
Zex odoc h ium
c rrij icol klla .
This motli is found only in diseased bolls or in bolls that have been
attacked by
tlie bollworni.
It can
not
be considered of economic
iniiK)rtance to the cotton
croj).
I'l.AXT-r.rt;
( /'////( d
it'n iii
)
.
This i)lant-bug is commonly
found in St. Croix, but seldom
attacks
cotton.
Its
favorite
food
plant
is
the
fireweed
{Pdfura
metel).
Unless
the
field
is kept free of this weed.
P.
picta may
be
expected
to
attack cotton bolls.
The eggs are brown and are
deposited
in
clusters of 10 to
90
on
either
surface
of
the
leaves
of
fireweed
(Datura
inet('l).
They hatch
in from
4 to 8 days.
The nymphs are
red and congregate in groups.
The
adult
is dark brownish-
black.
Avith
a narrow orange-
red
line on
the
anterior and
lateral margins of the thorax,
and
a
broad
yellowish
or
orange-red band
on
the
l)os^
terior margin.
This band
is
absent
in some specimens.
I>otli adults and nymphs feed
by sucking the juice from the
plant.
(Fig. 21.)
CONTROL,
I'u;.
--'I,
-I'lithUi
ijicta: Adult
iii:il<
Much
en-
Picking l)y hand
is probably
the
l)est method of controlling
P. pirta on cotton.
The bugs can
(>asily be knocked into receptacles
containing water and kerosene
if tlie plant
is jarred.
SiMM.i)
SiTM-:-i!r(.
{.\rr<liii.s
a Ih'iini iicl al lis
)
.
'J'he si)ined stink-bug has not been found
in suHicient numbers to
lie of economic
imi)ortance.
Its habits and
life history
are almost
identical with those of the southern green stink-bug
iX."?((m
viri-
(hihi).
In its nymplud stage .1. allxfjuinrfafu.^ is dark reddish-brown
in color.
Measures ai'e not needed to control this insect.
20
BULLETIN
3, VIRGIX
ISLA]SrDS EXPERIMENT STATION.
Laege SqUxVSh Bug
{Leptoglossus gonogara).
The large squash bug
is more frequently found attacking guava
{Psidium guava) than any other plant.
These bugs rarely become
numerous enough on cotton to attract attention.
The eggs are laid in a single ro^Y, usually on the stem of the plant.
They hatch into red and black wingless nymphs, which molt several
times before reaching the adult stage.
The adult is a large brownish-
black bug.
Both nymphs and adults feed by sucking the juices from
the plant.
The large squash bug
is best controlled by hand picking.
The
nymphs and adults are easily brushed
into
a receptacle containing
water and kerosene.
The writer has made no effort to systematically collect the Orthop-
tera, Hymenoptera, Diptera, and Neuroptera that frequent the cot-
ton plant.
The three species of economic importance are the assassin
bug
(Zelus longipes), a praying mantis, and a lace-winged
fly or
aphis-lion.
These insects are predacious on insects attacking cotton.
Z. longipes
is found feeding on lepidopterous larvae and nymphs of
other Hemiptera.
The praying mantis feeds on a number of different
species, and the lace-winged fly in both larval and adult stages feeds
upon aphids.
COXTEOL.
MISCELLANEOUS NOTES.
o