ANR-409 Cotton Scouting Handbook
ANR-409, Reprinted March 1999.
Wheeler Foshee, Extension Associate;
Barry L. Freeman, Extension Entomologist,
Associate Professor, Entomology; C. Dale Monks, Extension
Crop Physiologist, Associate Professor, Agronomy and Soils;
Michael G. Patterson, Extension Weed Scientist,
Professor, Agronomy and Soils; Ronald H. Smith, Extension
Entomologist, Professor, Entomology; all with Auburn University
Cotton Scouting Handbook |
Table of Contents
Introduction
to Cotton Insect Scouting
Ronald H. Smith, Extension Entomologist
The Alabama Cotton Integrated Pest Management (IPM) Program
is an intensified educational program conducted by the Alabama
Cooperative Extension System. This program was initiated in 1972
and encompasses many phases of management and production. Some
of these components were ongoing prior to 1972. The prominent
practices that make up insect management on cotton are scouting,
the use of cultural practices, the use of economic thresholds,
and the proper use of insecticides and beneficial insects.
In the near future, new programs and technology will incorporate
additional components and advances to insect management. Two technological
advances are the boll weevil eradication program and the introduction
of the genetically altered "Bt" Bollgard varieties of
cotton that are tolerant to bollworms and tobacco budworms. Other
new selective chemistries are nearing development. Before the
turn of the century, a tremendous evolution in cotton insect management
will likely occur. Growers will need to stay informed of new technologies
that will impact scouting practices and what new insects will
emerge as economically important.
The primary objectives of this program are to help Alabama
cotton growers use all available methods of insect suppression
and use insecticides more economically and efficiently, thereby
increasing net profits.
Alabama is one of the leading cotton producing states in the
percentage of acres scouted annually. More than 85 percent of
the acreage in the state will be scouted weekly by a scout, trained
grower, or private consultant. The Alabama scouting program was
initiated in Pickens county in 1959 and has since expanded to
all major cotton producing counties of Alabama.
References
- "Cotton Pest Management Recommendations,"
Extension publication ANR-415.
- "Cotton Insect Infestation Report,"
Alabama Cotton Pest Management Program ANR-F11.
- "Cotton Aphids," Extension publication
ANR-845.
- "Soybean Loopers: Late Season Foliage
Feeders On Cotton," Extension publication ANR-483.
- "European Corn Borers," Extension
publication ANR-900.
- "Stink Bugs: New Economic Pests Of Cotton,"
Extension publication ANR-882.
- "Managing Bandedwinged Whiteflies On
Cotton," Extension publication ANR-901.
- "Fall Armyworms: Consistent Cotton Pests,"
Extension publication ANR-892.
- "Alabama Plan For The Management Of
Beet Armyworms," Extension publication ANR-842.
Back to top
Cotton: Morphology, Physiology,
Fruiting, and Development
C. Dale Monks, Extension Crop Physiologist
The cotton plant has an amazing ability to withstand adverse
weather conditions (cold, excessive rain, drought, etc.) and many
practices imposed by growers. Not only does the plant survive,
but it produces a decent yield of cotton under these conditions.
The genetics of cotton controls its basic behavior. Thus, when
a cotton seed is planted in conditions favorable for germination,
growth, and development in Alabama, we know how it will behave
under average conditions. We can expect the following schedule
of development: 1) From seed to emergence of a young plant averages
7 to 10 days in favorable conditions; in unfavorable conditions,
3 to 4 weeks. At this point, the plant has two cotyledonary leaves;
2) From emergence to first true leaf requires 8 or 9 days; 3)
From emergence to the appearance of first square averages 35 to
40 days; 4) From square to open blossom, 20 to 25 days; 5) From
open blossom to full-size boll, 25 days; 6) From full size-boll
to open boll, 30 days; 7) From blossom to open boll, 45 to 65
days.
Germination of Seed
Many things influence the ability of cotton seed to germinate,
but the best seed are those that have fully developed embryos,
have remained reasonably dry in the field and, after ginning,
have been stored in a relatively cool, dry place until planted.
In general, the drier the seed and the cooler the storage temperature,
the better the chance that the seed will retain viability and
vigor. Drying below 10 percent moisture is essential to safe storage
on the farm, even for a short period.
The reserve food supply of the cotton seed is stored in its
two cotyledons. The oxygen, moisture, and temperature requirements
for cotton seed are higher than for many other crop plants. Cotton
seed is very rich in oil and protein. These reserve foods require
large amounts of oxygen for conversion to the simple foods needed
in plant growth, much more than that needed for the conversion
of starch in seed such as corn and wheat. This high oxygen requirement
for germinating cotton seed explains the need for maintaining
good soil aeration, especially during germination.
Optimum germination of cotton seed occurs at a soil temperature
of 93 degrees F. The minimum soil temperature for both germination
and early seedling growth averages 60 degrees F and the maximum
about 102 degrees F.
Under conditions favorable for germination, the sprout pushes
through the pointed end of the seed in 2 to 3 days. The primary
root develops from the radical of the sprout and grows downward
into the soil. The cotyledons are carried well above the soil
by the elongating hypocotyl and unfold about 5 days after planting
if adequate soil moisture and temperature exist.
The Root System
The primary root of the cotton plant grows without branching
for several days and may have reached a depth of 9 inches by the
time the top emerges from the soil. Branch roots begin to develop
about the time the seedling straightens up and the cotyledons
begin to expand. The depth that the primary root penetrates depends
on the depth and character of soil layers, and on soil moisture
and aeration.
The location of most of the root system depends on the character
of the soil and the amount of moisture available. If the plant
grows in a soil that contains little moisture in the upper layers
but adequate moisture further down, the main root system usually
develops a considerable depth, up to 6 feet or more. But when
early growth is in fairly wet soil overlaying a compacted layer,
the greater part of the functional root system is usually shallow.
Leaves
The arrangement of leaves on a stem is known as "phyllotaxy."
Cotton leaves are arranged in a spiral with each leaf being 3/8 of a turn above the
last. A stem may have the leaves arranged in a right- or left-handed
spiral and occasionally you will see one that reverses direction.
The first true leaf of the central stem is usually not lobed.
As the plant matures, the leaves formed at higher positions are
more and more deeply lobed until the climax leaf shape is reached
at about the sixth to tenth position.
Nodes
The point on the stem from which the leaf originates is called
a node. The points where the two seed leaves or cotyledons are
attached are opposite and are the first node. This node is counted
as "0" when plant mapping. The point at which the true
leaf occurs becomes the first node and successively on up the
main stem.
Branches
There are two kinds of branches on cotton--vegetative branches
and fruiting branches. Vegetative branches have a development
pattern almost identical to that of the main stem. Each of them
develops continuously from an apical bud, and they often grow
nearly upright. At the lower nodes, the branch is always vegetative.
Usually, the vegetative branches occur in a definite zone near
the base of the plant, and the fruiting branches occur farther
up the stem.
The first fruiting branch is normally produced at the sixth
to ninth node on the main stem. This can be delayed by a number
of environmental factors such as: 1) exceptionally thick stands
(plant populations approaching 100,000 per acre and above); 2)
excessive nitrogen; 3) excessive rainfall resulting in waterlogged
soils at critical times; 4) late planting; and 5) insects (plant
bugs, bollworms, etc.). Fruiting branches tend to grow in a more
lateral position and have a somewhat zigzag appearance in contrast
to the straightness of the main stem and vegetative branches.
Once fruiting has begun, fruiting branches are produced at each
higher position or node.
Fruiting
As the fruiting branch grows from the main stem or from the
vegetative branch, it is terminated by a floral bud (square) and
a leaf. Any further growth of the fruiting branch occurs through
the development of an axillary bud at the base of the leaf that
accompanies the flower. Termination of one growing point by a
square and leaf, and the development of another growing point
from the bud at the leaf axil to form the next fruit form and
leaf, continues throughout the season and produces the zigzag
appearance mentioned previously.
The first square can usually be recognized in about 35 to 40
days after seedlings emerge. Twenty to 25 days are required for
it to develop into an open flower. Thus, cotton planted in mid
to late April will usually produce the first flower sometime in
late June. A flower is produced at the first node of the next
higher fruiting branch at intervals of about 3 days. Flowers appear
on successive positions of the same fruiting branch at intervals
of about 6 days. The number of squares produced is directly related
to the number of fruiting branches and their fruiting positions.
Peak blooming usually occurs about a month after first bloom,
levels off for 2 to 3 weeks, and then declines rapidly.
Shortly after the flower opens, the anthers split open and
discharge pollen which adheres to the sticky surface of the stigma.
Pollination usually occurs without the aid of insects because
of the closeness of the stigma and anthers. Very little pollen
is disseminated by air movement. The flower is white when it opens,
then closes and turns pink after 24 hours.
The Boll
The ovary (boll) develops rapidly after fertilization and reaches
full size after about 21 days. An additional 20 to 50 days elapse
before the boll is mature and ready to open, depending primarily
on temperature. Bolls from flowers opening during July mature
much more rapidly than bolls from flowers opening during late
August.
The size of the boll varies with variety, soil fertility, soil
moisture, and cultural practices. Usually, 50 to 90 bolls are
required to make a pound of seed cotton. When bolls mature, the
carpel walls dry and split along the lines where the carpels meet.
In favorable conditions, the bolls open rapidly, and the locks
of cotton dry and fluff within a period of 3 to 4 days. The number
of locks corresponds to the number of carpels and varies from
three to five. The number of seeds per lock is about nine.
Development of Seed and Lint
The fertilized ovule (developing seed) enlarges rapidly, reaching
its maximum volume about 3 weeks after blooming. About 2 weeks
prior to the opening of the boll, the seed is completely filled
by the embryo, which has already become differentiated into sprout
and seedling leaves. However, maximum weight is attained only
a few days before the boll opens. Most of the oil and protein
accumulates in the embryo during the second half of the boll maturation
period.
Each cotton fiber originates from an extension of a single
cell on the outer layer of the seed coat. These cells begin to
elongate about the time the flower opens. They continue to elongate
as thin-walled tubular structures until maximum length is reached,
usually about 18 to 20 days after blooming. Fiber length is shortened
considerably by a shortage of water if it occurs during the period
of fiber elongation. After the fibers reach their maximum length,
the fiber walls are thickened by the deposit of consecutive layers
of cellulose on their inner surfaces in a spiral fashion.
Secondary thickening continues until just before the boll opens.
Secondary-wall structure never completely fills the cell, as some
space is always left in the center. The degree of thickening and
the angle of the spirals affect fiber maturity and strength. They
are dependent upon variety as well as environmental conditions
which affect growth and opening of bolls. Droughty conditions
during the wall thickening process usually increase fiber strength
slightly.
Until the boll opens, the cotton fiber is a living, cylindrical
cell. Moisture is lost from the fibers when the boll opens, causing
the fibers to collapse and die. As the fibers collapse, they assume
a flattened, ribbon-like form with few to many twists which help
cause the locks of seed cotton to fluff.
Shedding of Fruit
The cotton plant has tremendous fruiting potential. It produces
many more flowers than it can possibly mature. Only about 40 percent
of the fruiting forms produced under ideal conditions eventually
mature. This great reserve of fruiting forms effectively serves
to minimize loss in yield as a result of conditions temporarily
unfavorable for fruiting or from light infestations of insects.
Shedding may occur as a result of insect injury or as a result
of conditions attributed to the physiology of the plant. This
is called natural shedding. Almost all fruiting forms that shed
naturally are either very young bolls or very small squares. Young
bolls are more readily shed than small squares. Most squares over
one-third grown normally do not shed unless injured. Shedding
does not occur in the flower stage and only seldom in bolls more
than 10 days old.
Factors which adversely affect growth such as drought, flooding,
prolonged cloudy weather, unbalanced fertilizer, and root pruning
by deep cultivation are known to accelerate shedding temporarily.
When conditions become more favorable for growth, the plants compensate
by retaining a higher percentage of their later blooms.
Cut-Out
Usually, vegetative growth and flowering gradually decrease
and practically cease after the plants have become heavily loaded
with bolls later in the summer. The rather abrupt reduction in
growth and flowering is referred to as cut-out. Apparently, the
developing bolls have first claim to the plant's food supply produced
by photosynthesis and the nutrients absorbed by the root system.
Growth is slowed and finally stopped as the plant matures the
bolls that are already set. With the approach of cut-out, shedding
becomes very high.
In addition to the young bolls, many of the very small squares
are shed, especially if cut-out is abrupt. Many of the leaves
on the lower portion of the plant drop during this stage. The
cessation of vegetative growth and the loss of leaves on the lower
portion of the plant stimulate the rapid opening of bolls and
reduce losses from boll rot. Thus, the occurrence of cut-out is
desirable unless it occurs so early that yield is reduced.
The degree and time of cut-out are influenced by variety as
well as environmental conditions such as insect control, weather,
and soil fertility. High rates of nitrogen, particularly in combination
with high rainfall during late summer and early fall, are very
conducive to continued vegetative growth.
NOTE: This section was originally prepared
by Louie J. Chapman, Former Head of Extension Agronomy.
Back to top
Cotton Insect Pests
Barry L. Freeman, Extension Entomologist
The proper recognition of the many different insects found
in cotton fields is essential to the efficient management and,
frequently, the profitability of the crop. Although more beneficial
insect species than pest species occur in cotton, pest populations
can reach tremendous levels and do extensive crop damage. To maintain
pest populations below damaging levels, by efficient management
of natural enemies, chemical suppression, or other means, requires
a thorough understanding of their life cycles and relationships
to host crops and to other organisms.
Boll Weevil (Anthonomus grandis)
DESCRIPTION: Adult boll weevils are hard-bodied insects about
1/4 inch long. They
have chewing mouthparts at the end of a slender, curved proboscis
or snout, which is approximately half the length of the body.
Newly emerged adults are reddish-brown to gray, and they darken
with age. The elytra (wing covers) are longitudinally striated
and are clothed with short, silver-gray hairs. Spurs are present
on the inside of the front femurs (Figure 1).
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Figure 1. Boll weevil adult. |
The larvae are off-white, legless, wrinkled grubs with brown
heads. They attain a maximum length of 3/8 inch.
The pupae are white and somewhat resemble the larvae in shape,
but have their appendages folded loosely against the body.
The boll weevil immigrated to the United States from Mexico
in 1892 and to Alabama in the early l900s. Because the boll weevil
did not have the natural enemies that many native pests do, control
of the weevil has been heavily dependent on chemical insecticides.
The majority of chemicals used to combat the weevil have resulted
in the destruction of parasites and predators of other pests,
often resulting in a status change of these pests from secondary
to primary pest. In fact, after the elimination of their natural
enemies, some of these pests have superseded the boll weevil in
destructiveness and in difficulty of control.
A massive program to eradicate the boll weevil from the United
States is underway. For the most part, this program has eliminated
the boll weevil from Alabama and eastward. At the present time,
boll weevils remain west of Alabama and the future of eradication
efforts in those areas is in some doubt. As a result, reinfestations
of boll weevils in Alabama cotton is a possibility.
The boll weevil overwinters as an adult in a variety of well-drained,
protected places surrounding cotton fields. The majority of surviving
weevils come out of hibernation and enter cotton fields in May
and early June if moisture is adequate. Cotton is the only plant
on which the boll weevil can reproduce.
Before squares form, feeding is limited to tender terminal
growth and leaf petioles. These damaged plant parts often wither,
turn dark and droop, creating black flag damage.
As the first squares become one-third grown, female weevils
chew a small hole (usually in the bottom half of the square) deposit
an egg, and seal the hole. Some overwintered weevils will not
seal the ovipositional punctures; however, later in the season
most of the punctures will be sealed with a gelatinous material,
creating a distinctive tit-like appearance on the square. Eggs
hatch in 3 to 5 days and the larvae begin feeding. As the larvae
continue to feed and develop, the squares flare, turn yellow,
and fall to the ground.
The larvae feed a total of 7 to 12 days and then pupate within
the square. Pupation lasts for 3 to 5 days and then the new adult
weevils emerge. Before a new weevil can lay eggs, 3 to 7 days
are spent feeding, locating a mate, and mating. Later in the season,
eggs may be deposited in young bolls, which may or may not fall
from the plant. A complete life cycle requires about 3 weeks.
Cotton Bollworm (Helicoverpa zea) & Tobacco Budworm
(Heliothis virescens)
DESCRIPTION: The bollworm moth (this species is also known
as the corn earworm) is buff colored and 3/4 to 1 inch long. A dark spot is present near
the center of each forewing and a dark band traverses the wings
behind this spot; however, this band often becomes worn with age.
There is also a dark transverse band near the posterior margin
of the hind wings (Figure 2).
The adult budworm is slightly smaller than the bollworm moth
and is cream colored with distinctive greenish bands across the
forewings (Figure 3).
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Figure 2.
Bollworm moth |
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Figure 3. Tobacco
budworm moth |
The larvae (worms) of both species are very similar and attain
a maximum length of 1-1/2
inches. Color varies from green to yellow to pink. Both possess
three pairs of thoracic (true) legs, four pairs of abdominal prolegs,
and one pair of anal prolegs.
The eggs of both species are spherical and about the size of
a pinhead. Close inspection reveals ridges running from top to
bottom. Eggs are normally deposited singly and first appear pearly-white,
but they darken with age.
These two insects damage cotton similarly and can be found
in the same fields. Generally speaking, the June generation is
mostly tobacco budworms, the July generation is a mixture, and
in late season, the budworm is usually dominant.
Each female moth may lay 1,000 or more eggs. The eggs are often
deposited on the tops of leaves in the terminal of the plant,
but they may also be found on square or boll bracts, stems, and
dried blooms. The egg stage lasts for 2-1/2 to 4 days.
The eggs hatch into small larvae which feed on terminal growth,
squares, blooms, bolls, and occasionally, leaves. As the larva
matures and each square or boll is consumed, it moves on to another,
damaging several fruiting forms during its 14- to 21-day life.
Generally, each larva will work its way down the plant, attacking
larger fruit. The full-grown larva finally drops to the ground
and pupates in the soil. The adult emerges 10 to 14 days later.
The average length of the life cycle is 30 to 40 days. The overwintering
stage is the pupa.
Tarnished Plant Bug (Lygus lineolaris)
DESCRIPTION: Adults are predominately straw to dark brown and
mottled with red, yellow, and black. They are about 1/4 inch long. The wingless nymphs are green,
similar in appearance to the adults, and attain a maximum length
of 1/4 inch. The
older nymphs possess wing pads and distinctive black spots (Figure
4).
Figure 4. Tarnished
plant bug
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nymph |
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adult |
The tarnished plant bug overwinters as an adult and completes
one or two spring generations on a variety of wild hosts, including
fleabanes, wild carrot, dock, mustard, and many legumes. A few
plant bugs may develop on cotton during May; however, the main
migration to cotton is in June. Cotton is not a preferred host
of the tarnished plant bug and the adults constantly search for
a better host.
As plant bugs enter cotton, they begin feeding and laying eggs.
The egg stage is rather long, 7 to 14 days. During this time,
the population is predominately adult. As the eggs begin hatching,
usually the latter half of June, populations contain many nymphs.
There are five nymphal stages requiring 2 to 3 weeks for development.
Plant bug populations decline naturally during July.
Both adult and nymphal plant bugs have piercing-sucking mouthparts
to suck plant juices from tender tissue. They may damage all fruiting
forms of cotton, but the most damage is to pinhead squares. Adults
and larger nymphs do significantly more damage than do the smaller
nymphs.
After a pinhead square has been damaged, it turns brown and
soon falls from the plant. No outward appearance of damage is
present on squares fed upon by plant bugs. Plant bug feeding in
the terminal of the plant can alter the physiology of the plant,
resulting in what is often referred to as crazy cotton.
Often associated with this condition are split lesions on the
stems and leaf petioles, aborted terminals, fruitless lateral
branches seeking dominance, and swollen nodes and leaf petioles.
In general, a tall, spindly, and relatively fruitless plant develops.
Damage to large squares is inconspicuous, but as the blooms
open, the damage becomes evident. The anthers are darkened and
warty spots can be seen on the petals. Heavy feeding by plant
bugs on large squares can cause abortion, but most often the result
is poor pollination and deformed bolls.
Direct boll feeding by tarnished plant bugs does occur. Boll
injury appears as small, dark sunken spots on the outside of the
boll. Severe feeding on young bolls may cause the bolls to shed,
but more often, localized lint and seed damage is the result.
Unlike many of the other cotton insect pests, the number of
tarnished plant bugs do not necessarily represent how much damage
will be incurred. Therefore, the pinhead square retention of a
field must be monitored along with the numbers of plant bugs before
a logical control decision can be made. Years with cool, rainy
conditions during June are most often the worst plant bug years.
There are several other plant bugs which may attack cotton.
The most common of these are the clouded plant bug, Neurocolpus
nubilus, and the cotton fleahopper, Pseudatomoscelis seriatus.
Damage to cotton by these insects is similar to that of the tarnished
plant bug.
Spider Mites (Tetranychus urticae)
DESCRIPTION: Spider mites are very small, wingless arthropods
closely related to insects. Color is variable, including yellow,
red, and straw-colored forms. There are several life stages, including
six-legged larvae and eight-legged nymphs and adults. The two-spotted
spider mite is so named because of two dark areas on the sides
of the abdomen which are actually the gut contents visible through
the exoskeleton.
Although several species of spider mites damage cotton in Alabama,
the two-spotted spider mite is the most common. It is more frequent
in northern Alabama than the rest of the state.
Mites damage cotton by sucking plant juices from the bottom
surface of leaves. Damage varies from a light mottling of leaves,
to severe mottling and discoloration, to defoliation.
Mite infestations arise locally near field margins in weed
clumps, around power poles, etc. They prosper in warm, dry weather.
Since mites do not fly and crawling is inefficient, widespread
mite infestations can be a result of mechanical dispersal by farm
machinery, people moving through fields, and windy weather.
The spider mite life cycle is short, about 15 days, and high
populations can be reached quickly. However, mites are very susceptible
to predation and certain diseases, which is one reason some insecticides
cause a mite outbreak.
Thrips (Frankliniella spp.)
DESCRIPTION: Adult thrips are small (1/20 to 1/16
inch), slender insects and are yellow to black. Their developed
wings are long, slender, and fringed with hairs.
The larvae of thrips are similar to the adults but are smaller
and have no wings. Wing pads are developed in the later instars.
Unlike some other cotton insect pests which are sporadic, the
tobacco thrips, F. fusca, the flower thrips, F. tritici,
the western flower thrips, F. occidentalis, and others
tend to be a chronic problem. In early spring as soon as cotton
emerges, thrips migrate from a multitude of wild hosts to cotton.
Thrips use their rasping mouthparts to rupture plant cells and
imbibe the released contents.
Heavy thrips feeding results in ragged, split leaves which
are often cupped upward. When fed upon by thrips, the cotyledons
often appear silvery on the bottom surface. Heavy thrips damage
delays maturity and lowers yields. As temperatures warm and cotton
begins to grow vigorously, thrips are still present but are generally
no longer considered harmful.
Thrips deposit eggs in tender plant tissue, and a generation
is complete in about two weeks. There are multiple generations
each year in Alabama.
The western flower thrips is a native of the western United
States. It appeared in the southeast around 1980 and is now common
throughout Alabama. In addition to being a pest of seedling cotton,
the western flower thrips is also a pest of in-season cotton.
During the dry weather of the spring or summer, huge migrations
of western flower thrips often occur. This insect is not as easily
controlled as other species of thrips.
Cotton Aphids (Aphis gossypii)
DESCRIPTION: Adult aphids (plant lice) may be winged or wingless.
They are small (about 1/14
inch), pear-shaped, soft-bodied insects with sucking mouthparts.
Color varies from yellow to green to nearly black.
The nymphs are similar in appearance to the adults; both have
two tube-like structures (cornicles) on the top of the abdomen
(Figure 5).
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Figure 5. Aphid |
Winged aphids enter cotton in spring or early summer and give
birth to live young. Aphids damage cotton by sucking plant juices,
which lowers plant vigor and causes the damaged leaves to crinkle
and cup downwards. During the feeding process, a sugary secretion
called honeydew is produced on which sooty mold grows. If this
occurs after the bolls open, the lint is stained, and the quality
of the cotton may be significantly reduced.
Aphids have a tremendous reproductive potential, and if unchecked,
they can attain huge populations in a short time. They are, however,
extremely vulnerable to predation and parasitism. Aphids may,
on occasion, cause severe damage to seedling cotton. This normally
occurs in cool weather which permits aphid reproduction but retards
the reproduction and subsequent increase in natural enemies.
During the 1970s, the cotton aphid was a rare mid and late
season pest of cotton. Due to changes in the class of insecticides
used to control other cotton pests, the cotton aphid now has established
itself as a consistent pest of mid and late season cotton in most
of Alabama. Cotton aphids are tolerant to most insecticides. Control
is usually realized from the effects of a fungal pathogen, Neozygites
fresenii. When this disease becomes present, virtually the
entire aphid population succumbs in a matter of days. This usually
occurs in July.
Cutworms (Several species)
DESCRIPTION: Moths have mottled brown to gray front wings with
a wingspan of 1-1/4
to 1-1/2 inches.
The hind wings are often more uniform and have a lighter color
than the front wings.
Cutworm larvae appear soft, fat, and greasy and attain a maximum
length of about 1-1/4
inches. When disturbed, the larvae curl up and remain motionless.
Some of the more common cutworms in Alabama are: the granulate,
Feltia subterranea; the variegated, Peridroma saucia;
the black, Agrotis ipsilon; and the climbing cutworms.
Cutworms spend the day in the soil, coming out at night to feed.
Damage to cotton is primarily confined to the seedling stage.
Small larvae often feed on leaves producing an irregular hole.
Medium and large larvae often cut off young plants just above
ground level.
Cutworm damage is normally dispersed enough to attract little
attention; however, at times they may be concentrated enough to
threaten the stand. This usually occurs in low areas, on new ground,
and in places with heavy weed competition. Cutworm populations
have been more common in cotton produced with minimum tillage
practices.
Cabbage and Soybean Looper (Trichoplusia ni & Pseudoplusia
includens)
DESCRIPTION: The adults are mottled gray to black moths with
a wingspan of 1-1/4
to 1-1/2 inches.
The hind wings are a lighter color than the forewings.
The larvae are predominantly green with pale white stripes
down the back and sides. Maximum length is 1-1/2 inches. There are three pairs of thoracic
legs, two pairs of abdominal prolegs, and one anal pair of prolegs.
The soybean loopers usually can be distinguished by black thoracic
legs.
The eggs of loopers are similar to those of bollworms but are
somewhat flattened and are placed on the bottom side of leaves.
Looper eggs are deposited by night, and the larvae feed on
cotton leaves for 2 weeks or longer before pupating. Pupation
occurs within a web on the underside of leaves. Cabbage loopers
seldom require chemical control due to the incidence of natural
control agents. One of the common natural controls is a viral
disease which can be evidenced by the black, slimy remains of
the larvae hanging from leaves. Soybean loopers can be a serious
pest and may entirely defoliate cotton.
Fall Armyworm (Spodoptera frugiperda)
DESCRIPTION: The moths have dark gray forewings with some mottling.
The hind wings are a much lighter color and are bordered by a
dark band. The wingspan is about 1-1/4 inches.
Fall armyworm larvae reach a maximum of 1-1/2 inches. In cotton, the larvae are usually
grayish with lighter stripes running the length of the body. There
is normally a light-colored inverted Y on the front of the head.
On many specimens, especially when small, a dark spot can be found
on the sides of the first abdominal segment.
The cervical shield (top of the neck area) is dark with three
lighter colored longitudinal stripes which are continuous with,
but more conspicuous than, those on the body. The most consistent
identifying characteristic is the four circular scleratized plates
atop the eighth abdominal segment. These plates are arranged in
a small square and are plainly larger than the spiracles found
on the sides of this segment.
Eggs are whitish and deposited in groups of up to 150. The
egg masses, which may be two or three eggs deep, are concealed
with a layer of scales from the moth. Although the eggs may be
placed anywhere on the plant, they are usually found on the bottom
of fully expanded leaves.
The fall armyworm overwinters south of the freeze line and
begins its northward migration as the weather warms. Cotton in
Alabama is always infested by some fall armyworms. The size of
these populations is dependent, evidently, on weather conditions,
especially during the development of early generations on alternate
grass hosts. Problems with fall armyworms are fairly consistent
in extreme southern Alabama.
As the egg masses hatch (2 to 10 days), the young larvae disperse
and will feed on leaves, blooms, squares, and bolls. Larval development
requires 12 or more days. When full grown, the larvae burrow beneath
the soil surface and pupate. In about 2 weeks, the adults (moths)
emerge to begin a new generation.
Unlike bollworms and budworms, fall armyworm larvae may begin
their feeding on large squares and bolls, are often found in higher
numbers in drought-stressed portions of the field, tend to occur
further down the plant, and, on the average, spend more time feeding
on an individual fruiting form. When young fall armyworm larvae
attack large fruit, their first damage is often an etching on
the inner surface of bracts, resulting in a characteristic window
pane damage. Fall armyworm survival is often quite poor.
Beet Armyworm (Spodoptera exigua)
DESCRIPTION: The beet armyworm moth is about 3/4 inch long. The forewings are grayish or brownish
and have a pale spot near the center. The hind wings are white
and have a fringed border.
The eggs are deposited in masses, usually on the bottom of
leaves, and appear fuzzy, somewhat like the egg masses of the
fall armyworm.
The larvae vary from pale to dark olive green, have a dark
stripe down the back, pale stripes down the sides, and reach a
maximum length of 1-1/4
inch. A characteristic black spot is located above the second
pair of thoracic (true) legs. This spot is often obscured by a
dark lateral line. Do not confuse the beet armyworm with other
armyworms which often possess an evident spot on the side of the
first abdominal segment.
The newly hatched larvae feed en masse, skeletonizing leaves
near the oviposition site. As they mature they disperse, eating
the foliage as they go. Infestations often begin on open grown
plants; for example on the ends of rows, in skippy stands, etc.
Although mainly a defoliator, the beet armyworm will damage squares
and small bolls and even bore into the stalk. This insect is capable
of reaching high populations by late season and may defoliate
a considerable amount of cotton.
Whiteflies (Trialeurodes abutilonea)
DESCRIPTION: Adult whiteflies are small (1/16 inch) and resemble tiny moths. The bandedwinged
whitefly is dusty-white with several dark bands across the wings.
With the exception of the first instar, the immature stages
are sessile, found attached to the bottom of leaves, and somewhat
resemble scale insects.
Whiteflies have piercing-sucking mouthparts that damage cotton
by extracting plant juices. Further damage is caused by the excretion
of honeydew and, subsequently, the growth of sooty mold on leaves
and open bolls. Whitefly populations generally peak in late season,
when a generation requires 2 to 3 weeks for development.
The silverleaf whitefly, Bemisia tabaci, is a serious
pest of cotton in the southwestern portions of the cotton belt.
It has been found in southern Alabama and may occur alone or with
the bandedwinged whitefly. The life history of the silverleaf
whitefly is similar to that of the bandedwinged whitefly. The
adults lack dark bands on the wings.
Stink Bugs (Nezara viridula)
Stink bugs, primarily the southern green stink bug, may occur
as a mid to late season pest in any area of the state (Figure
6). In the past, stink bugs have been controlled mostly by insecticide
applications for other pests. As these applications are reduced
it is likely that stink bugs will become a more common pest. Both
adult and nymphal stink bugs pierce young soft bolls and feed
on the developing seeds within. Their damage is best observed
by slicing the bolls to reveal the necrotic tissue caused by their
feeding. Stink bug eggs are laid in masses on plant foliage. The
eggs are metallic colored before hatching and are shaped like
tiny barrels with spiny rims. Stink bugs can be observed visually
and some idea of abundance can be gained through sweep net or
drop cloth samples. Their presence can sometimes be detected by
smell.
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Figure 6. Stink bug |
Other Insects in Cotton
The yellow-striped armyworm, Prodenia ornithogalli,
may be found on cotton throughout the state, but is more common
in northern Alabama. The larvae are velvety black with yellow
longitudinal stripes. They are mainly leaf feeders but will occasionally
damage squares and young bolls.
The cotton leafworm, Alabama agrillacea, is a
voracious leaf feeder and may be found in large numbers late in
the season. Cotton leafworm larvae are slender and reach a length
of 1-1/2 inches.
Color varies from yellowish green to near black. There are white
stripes running down the back and sides and two rows of black
spots down the back. This insect does not overwinter in the United
States and must migrate from the tropics each year.
The European Corn Borer, Ostrinia nubilalis,
and the Common Stalk Borer, Papaipema nebris, bore
into cotton plant stalks, causing the tops to wither, die, and
eventually break over. Young European corn borer larvae often
are found inside leaf petioles before moving to larger stems.
This insect also may be found attacking squares and bolls.
There are other insects which are found in cotton but seldom
cause economic damage. They include leaf rollers, wooly bears,
grasshoppers, flea beetles, grape colaspis beetles, cucumber beetles,
leafhoppers, cotton square borers, white-fringed beetles, leaf
miners, seed corn maggots, salt marsh caterpillars, southern armyworms,
and others (Figure 7).
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Figure 7. Leafhopper |
Back to top
Beneficial Insects in a
Cotton Insect Pest Management Program
Barry L. Freeman, Extension Entomologist
Beneficial insects play an important role in moderating the
damage caused by pest insects. Sometimes their effect can be most
dramatic and almost complete, but more often their benefit is
more subtle. Beneficial insects are important because most of
our damaging pests were imported into this country without their
complement of native natural enemies. With the boll weevil no
longer a cotton pest and with advances in insect control via transgenic
cotton, the importance of beneficial insects will be greatly increased.
Generally, beneficial insects do not occur commonly unless
there is a source of food. As a result, there is usually a lapse
of time between the appearance of a pest insect population and
the activity of beneficial insects. This is called lag time and
many factors can influence its duration.
Another general but important point is that the effect of beneficial
insects is usually greater when more than one species is involved.
Many species of beneficial insects can be important in cotton
pest management programs. At least 600 different species of beneficial
insects have been identified in the cotton insect community. Some
of these species are very common and others are only observed
on occasion. Some species are only involved with one pest species
while others are involved with many pest species.
Beneficial insects can be separated into two broad groups:
predators and parasitoids. Predators attack and feed on other
animals (prey). The prey species are usually smaller and weaker
than the predators. Many prey are consumed during the life of
the predator. Parasitoids feed in or on another living animal
(host) for a relatively long time. They consume a substantial
amount of tissue and eventually kill the host. Each parasitoid
normally develops on and kills only one host.
Predators
Hemiptera
Orius insidiosus, often called the minute pirate bug
or flower bug, is a predator of eggs and the first instar larvae
of the bollworm, budworm, thrips, and other small insects (Figure
8). Big-eyed bugs, Geocoris spp., are common predators
of eggs and small larvae of the bollworm, budworm, other Lepidoptera,
mirids, thrips, and aphids (Figure 9). Damsel bugs of the genus
Nabis are efficient predators of a wide range of prey,
including mirids, leafhoppers, aphids, and eggs and larvae of
Lepidoptera (Figure 10). They attack bollworms as large as the
second instar. Assassin bugs, particularly the genus Zelus,
feed freely on eggs and larvae of the bollworm, tobacco bollworm,
armyworms, and loopers (Figure 11). These insects are usually
more common in the southern portion of the state but are less
abundant than the predators previously discussed.
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Figure 8. Minute
pirate bug |
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Figure 9. Big-eyed
bug |
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Figure 10. Damsel
bug (nabid) |
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Figure 11. Assassin
bug |
Neuroptera
Larvae of green lacewings, Chrysopa spp., are important
predators of aphids and also attack the eggs and small larvae
of bollworms and other Lepidoptera. Brown lacewings can also be
common in some situations.
Coleoptera
Ground beetles of the family Carabidae have considerable potential
as predators in the cotton field, but knowledge is lacking on
the habits and factors affecting the abundance of the many species.
Lady beetles (Coccinellidae) are common predators in cotton fields
and are especially abundant in fields infested by aphids (Figure
12). Hooded beetles, Notoxus sp., are often abundant in
cotton. They reportedly feed on the eggs and small larvae of the
bollworm and other lepidopterous species (Figure 13).
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Figure 12. Lady
beetle |
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Figure 13. Notoxus
beetle |
Diptera
Many families contain species predaceous as adults or larvae.
Best known as predators in the cotton fields are the larvae of
syrphid flies that prey primarily on aphids.
Hymenoptera
Ants (Formicidae) include many predaceous species. Paper wasps,
Polistes spp., and many solitary wasps provide their young
with lepidopterous larvae. Fire ants are tremendous predators
and, if present, are often the dominant beneficial species.
Spiders
All spiders are predaceous and many species are common in cotton
fields. Orb weavers capture many moths in their webs. Wolf and
lynx spiders capture moths and other insects. Larvae and adults
of the bollworm and boll weevil adults are among the prey of jumping
spiders.
Parasites
Hymenoptera
Numerous hymenopterous parasite species of several families
are of great value in the biological control of cotton pests.
These parasites vary tremendously in size, behavior, ecology,
and host preference.
Almost every pest has several parasitic wasp species associated
with it. Cotesia sp., a parasite of the beet armyworm has
become rather well-known as has Trichogramma sp., a parasite
of various lepidopteran eggs.
Diptera
Tachinid flies commonly parasitize many types of caterpillars,
especially those which are exposed during feeding.
Back to top
Cotton Insect Survey
Techniques
Barry L. Freeman, Extension Entomologist
The main goal of cotton scouting is to estimate the pest populations
or pest damage in a particular field. Counts should represent
an average of what is in the entire field, not what was found
in the wet areas, dry areas, field edges, etc. It is absolutely
essential that all areas of the field are inspected because most
pests are not randomly distributed in a field.
Scouting is not a precise science. Different scouts invariably
get different counts from the same field; however, with a little
interest, training, and effort, counts will seldom vary enough
to influence the farmer's final decision.
Scouting for most major pests involves counting the number
of pests (or damaged fruit) per so many plants or plant parts
for conversion to a percentage. In your trek through the field,
you will be making counts for several different insects at the
same time. Therefore, it is imperative that notes of the individual
field counts be taken. These can be tallied and recorded back
at your vehicle.
Pencil is usually preferable to ink for field notes because
it does not run when wet. A hand counter can be an asset for certain
types of counts.
Several methods may be used to cover a field, depending on
field size, shape, and access. Time will not permit you to inspect
the entire field, so it is important to change your route from
week to week.
Quickly learn the location of fields and establish an approximate
schedule so that the farmer will have an idea of when and where
to find you. After field inspections are completed, transfer field
notes to the final inspection report and give them to the farmer.
Your scouting data is useless until it reaches the farmer.
At all times, keep an open channel of communication with your
employing farmers. And, above all, be honest!
Boll Weevil
The boll weevil has been eliminated from almost all of Alabama
and few scouts are monitoring this pest. The following section
is being retained in case there are isolated outbreaks or significant
immigration.
After the weevils begin laying eggs (about when the oldest
squares are one-third grown), scouting consists of determining
the percentage of weevil damaged squares. To do this, pull a few
squares from the plants as you walk and store them in a nail apron
until you have finished scouting the field. Your sample size should
be at least as large as the following:
- Fields of 1 to 20 acres: 50 squares
- Fields of 20 to 100 acres: 100 squares
- Fields of over 100 acres: 100 squares + 25 squares per additional
50 acres.
Pull only healthy-looking squares that are one-third grown
or larger and try to sample evenly from the top, middle, and bottom
portions of the plant. Vary the size of squares pulled, making
sure not to sample only large squares.
Never include squares from the ground, flared squares, or bolls
in your sample. Once you have finished inspecting a field, examine
the squares for weevil damage; both egg-laying punctures and feeding
punctures are considered damage. Record the weevil damage as a
percentage. The percentage is obtained by dividing the number
of damaged squares by the total number of squares collected and
then multiplying by 100.
Bollworms and Budworms
Since the eggs and worms (larvae) of these two insects are
very similar, they are normally lumped together in scouting. These
insects should be monitored throughout the season.
To determine the number of eggs and worms in the terminals,
closely examine the top 6 inches of the main terminal. After a
little experience, the eggs will be fairly evident; however, the
small worms are normally concealed in rolled-up leaves or small
squares of the terminal.
In fields where beneficial insects are active, many terminals
will exhibit worm damage, but the worm may have already been consumed
by a predator. It is a scout's job to determine if the insect
is still there. This is sometimes a difficult and tedious task,
but one of the most critical aspects of scouting.
Terminal samples should represent all areas of the field. Most
scouts find it easier to inspect five or ten terminals in several
locations than to sample single terminals here and there. Do not,
however, take your samples from a single row.
Later in the season and in drought conditions, many of the
eggs and small worms may occur below the main terminal. To detect
this activity, whole plant examinations or an expanded terminal
inspection will be necessary. These examinations are much more
time consuming than routine terminal inspections. If they become
necessary, the number of counts will have to be lowered to keep
you on schedule. Some observations of entire plants should be
made throughout the season to ensure detection of possible insect
problems which otherwise may not be noticed.
In addition to scouting for bollworm eggs and small larvae,
a damaged square count is also made. To do this, inspect the squares
which were pulled for the boll weevil sample and record the worm
damaged squares as a percentage. The number of live worms found
in this sample is not recorded but can indicate such things as
poor performance of previous insecticide applications, moth activity
down the plant, or poor scouting the previous week. This is also
a good way to pick up fall armyworm activity.
In the comments section, record the species and number of moths,
age of eggs, and size and location of worms, etc.
Much of the cotton planted in Alabama in the near future will
likely be resistant or tolerant to bollworms and budworms. Exactly
how these varieties should be scouted is not defined at this time,
but in all probability only a cursory examination will be made
for budworms and bollworms. It should be noted, however, that
these varieties will not prevent egg deposition and that newly
hatched caterpillars will have to feed a short time before they
are killed.
Spider Mites
Spider mites are scouted by general observation. Look for damage
first, and then turn the leaves over and examine them for mites.
The degree of infestation is recorded as follows:
- None: None observed
- Light: Spider mites found on an occasional plant
- Medium: Spider mites found on many plants; the leaves lightly
mottled yellow, red, or brown
- Heavy: Spider mites numerous on most plants; leaves appearing
reddish-brown
If a mite infestation is confined to the edges or a part of
a field, as is often the case, this should be noted in the comments
section.
Cotton Aphids
General observations for aphids and their damage are used to
monitor populations. Record the degree of infestation as follows:
- None: None observed
- Light: Aphids found on an occasional plant
- Medium: Aphids found on many plants; some leaves curling
along edges
- Heavy: Aphids numerous on most plants; honey dew evident;
crinkling of leaves present; chlorotic terminals common
Seedling Thrips
Usually, cotton has surpassed the stage of being susceptible
to thrips injury by the time most scouts begin examining fields.
In general, thrips are scouted for by random observations of the
insects and their damage while walking the field. Adult thrips
can be counted on a row-foot basis by shaking plants over a sheet
of paper or into a box. Normally, it is sufficient to record thrips
damage as follows:
- None: No thrips or damage found
- Light: Only occasional thrips found; newest unfolding leaves
without brown edges and crinkling; no silvering of the bottom
of leaves
- Medium: Thrips found readily; most of the newest leaves showing
browning of edges and crinkling; many of the leaf bottoms silvery
- Heavy: Thrips numerous; terminal of plant showing injury;
silvering of leaves very noticeable; plant's general appearance
ragged, deformed and stunted
Western Flower Thrips
Monitor western flower thrips by observing insects and their
damage from early bloom through cut-out. Numbers of thrips per
bloom can be estimated by visually bisecting the bloom, counting
the thrips on one side, and multiplying by 4. Four is used due
to the numbers of thrips hidden among overlapping petals and between
petals and bracts. Infestations should be recorded as follows:
- None: No thrips or damage observed
- Light: Less than 20 thrips per bloom; callous tissue on leaf
ribs and smutted nectaries found on an occasional plant; first-day
blooms healthy
- Medium: 20-80 thrips per bloom; callous tissue and smutted
nectaries common; some first-day blooms appearing wilted and
off-color
- Heavy: 80 or more thrips per bloom; callous tissue on leaf
ribs and smutted nectaries obvious and present on most plants;
numerous first-day blooms appearing wilted and off-color
Whiteflies
To determine whitefly infestations, observe the whiteflies
and their damage as you scout the field. Record the degree of
infestation as follows:
- None: None observed
- Light: Whiteflies found in the terminal of an occasional
plant
- Medium: Whiteflies observed in terminals of many plants;
some honeydew found on lower leaves
- Heavy: Whiteflies numerous in the terminals of most plants;
honeydew clearly evident
Plant Bugs
Plant bugs should be monitored at least weekly from the time
the first plants begin squaring until mid to late July or when
the farmer begins a scheduled control program. A good method for
sampling plant bugs is to vigorously shake plants over a drop
cloth; then simply count the number of plant bugs and record on
a row-foot basis. Most drop cloths are 3 feet long; therefore,
if one row is shaken, the sample is 3 feet; if both rows are shaken,
the sample is 6 feet. Both the adults and nymphs are counted.
The adults will fly, so count them quickly. For the most accurate
counts, some adults will have to be noted as you shake the plants.
The small nymphs are difficult to see. Make a thorough examination
so as not to overlook these.
If cotton fleahoppers, clouded plant bugs, or other plant bugs
are noticed, record them in the comment section.
Although not as reliable, a sweep net can be used for plant
bug sampling. The numbers found should be recorded as numbers
of plant bugs per so many sweeps.
In addition to sampling plant bugs themselves, a pinhead square
retention count should be made. Inspect one pinhead square in
the terminal of plants, note if it is good or bad, and record
the percentage of healthy pinhead squares.
Probably the easiest way to make this sample is to inspect
one square in each of ten terminals in several locations. Only
sample one square per terminal. A leaf 1 to 2 inches in diameter
will be associated with the size square you should be sampling.
Picking this leaf out and then inspecting the square associated
with it, before actually looking into the terminal, will prevent
sample bias.
The pinhead square on the first differentiated limb beneath
the plant terminal is often favored by plant bugs. This square
should comprise a large portion of your sample. The leaf associated
with this square will be furled.
Since adult plant bugs are difficult to accurately sample by
any method, emphasis should be placed on pinhead square retention.
If adult plant bugs are commonly observed but not reflected in
drop cloth samples, this should be noted.
Beneficial Insects
Most of the beneficial insects you will be concerned with are
predators of the bollworm. Some of the more important ones are
big-eyed bugs, nabids, minute pirate bugs, damsel bugs, lacewings,
and lady beetles. Spiders, although not insects, are also important
predators.
During other scouting activities, especially the plant bug
samples, you will see beneficials. This will give you a good feel
for their abundance. An addition to the beneficials themselves,
you should also note their effects; that is, a high proportion
of one-day-old bollworm eggs or numerous terminals showing damage
from small worms but with no worms present. Also, a variety of
beneficials in a field is indicative of a healthy population.
Light, medium, or heavy (L,M,H) is generally sufficient for
denoting beneficial populations. After the start of hard insecticide
treatments, beneficial insect populations decline and are of less
interest.
Others
There are other insects which at times may be bothersome but
can only be recorded in the comment section of the infestation
report. Some of these include fall armyworms, beet armyworms,
loopers, and stink bugs. If these occur, make a note and try to
give the farmer an idea of abundance and amount of damage.
Back to top
Pesticide Safety for
Scouts
Wheeler Foshee, Extension Pesticide Education Specialist
Cotton scouts have an excellent safety record with pesticides.
Nevertheless, pesticides can present certain hazards. Individuals
scouting fields for pests and pest problems need to be aware of
the chemicals being used by farmers, the general toxicity of the
chemicals, and the effects pesticides can have on people. Safety
is a topic that cannot be overemphasized. Safety is a frame of
mind or an attitude you develop and practice for your well-being
and for that of the public. A lack of knowledge about pesticides
is the basic reason in most adult pesticide-related injuries.
There are three routes of entry to the human body by a chemical.
These are dermal, respiratory, and ingestion. Dermal exposure,
during formulation and application in the field, has been reported
as the more critical type of exposure to humans. The following
factors affect dermal exposure and skin penetration: 1) Physical
and chemical properties of the pesticide; 2) Health and condition
of the skin; 3) Temperature; 4) Humidity; 5) Presence of other
chemicals (solvents, surfactants, etc.); 6) Concentration of the
pesticide; and 7) Type of formulation.
Collectively, the factors affecting absorption will influence
dermal toxicity. Of the factors listed above, only the health
and condition of the skin are independent of these factors. Concentration,
physical and chemical properties of the pesticide, and the presence
of other chemicals are established by the manufacturer or farmer.
Temperature and humidity are the environmental conditions existing
at the time of application, often established for favorable and
effective pest control. Persons with cuts, abrasions, scratches,
scuffs, or any other skin damage should exercise caution by minimizing
exposure of such areas to pesticides.
Skin absorption increases as you perspire. Skin pores open
in response to increased body temperature. This allows for faster
and increased chemical absorption. To prevent skin absorption,
wear a long-sleeved shirt of tightly woven material to protect
your arms. Try not to enter the field immediately behind application
equipment.
Fields that have been treated with foliar insecticides classified
as highly toxic should not be entered, and plant foliage should
not be handled for at least 24 hours to protect you by minimizing
dermal exposure. Worker Protection Standards (WPS) require that
scouts use the appropriate Personal Protective Equipment (PPE)
if entering a field before the Restricted Entry Interval (REI)
has expired (see pesticide label). To minimize dermal exposure:
1) Use clean clothing daily; 2) Bathe or shower daily; 3) Avoid
wearing canvas shoes when plant foliage is wet from dew; 4) Avoid
entering any field that has recently been treated; 5) Avoid wiping
face or forehead with shirt sleeves; 6) Avoid rubbing eyes with
contaminated hands; and 7) Wear long-sleeved shirts and full-length
trousers.
Exposure by oral ingestion is usually caused by not practicing
proper personal hygiene. Accidental ingestion has occurred when
applicators were loading spray equipment. Scouts can minimize
oral exposure by following these procedures: 1) Never eat or drink
while handling pesticide-treated plant parts; 2) Always wash hands
and face with soap and water before eating; 3) Do not wipe mouth
with hands; and 4) Do not chew on treated plant parts.
Respiratory exposure is not a threat to scouts if other precautions
are followed. Some of the highly toxic organophosphates may volatilize
or cause a vapor-like action within the field shortly after being
applied. For this reason and because of dermal contact possibility,
many products have a 24 or 48 hour reentry time. Check label for
restricted entry interval (REI).
A scout should be familiar with the general chemicals used
by each farmer and know what reentry interval is safe to follow.
The current pesticide label will carry particular warnings on
reentry of fields after treatment and other special precautions.
A scout should know the symptoms of pesticide poisoning so
that medical attention can be sought if needed. Symptoms of blurred
vision, abdominal cramps, tightness of chest, nausea, diarrhea,
headache, and confusion are associated with organophosphate poisoning.
Medical attention should be obtained promptly if symptoms exist.
All pesticide labels have suggested antidotes for accidental poisoning
treatment. Poison Control Centers have current antidote treatment
information and can be reached 24 hours a day by any physician.
The Poison Control Center at Children's Hospital in Birmingham
can be reached by calling toll-free, 1-800-292-6678, from anywhere
in Alabama.
Some scouts may develop a rash or skin condition because of
an unusual sensitivity. If, as a scout, this condition should
occur, try an oil skin lotion before entering fields. Commercial
preparations are available to prevent skin absorption and to act
as a protectant.
* This section was originally prepared by
G. Talmadge Balch, former Extension Pesticide Education Specialist.
Back to top
Herbicide Injury to Cotton
Michael Patterson, Extension Weed Scientist,
and C. Dale Monks, Extension Crop Physiologist
As a cotton scout, you must be able to identify various insects
found in cotton and recognize the damage or benefit resulting
from their presence. However, you should be able to recognize
other agents that injure cotton or cause it to be abnormal in
appearance. One such group of agents is herbicides.
Virtually all the cotton in Alabama receives at least one herbicide
application. Most of the acreage you scout will have had several
applications, and possibly as many as four different herbicides
used during the season. You will very likely encounter some injury
to plants or plants that are abnormal in appearance as a result
of the use of pesticides.
The majority of the cases of injury result from misuse and/or
carelessness in the application of herbicides to cotton or to
other crops nearby.
- Phenoxy injury. One of the most common types of injury
encountered during the time you will be in the field is caused
by phenoxy or related compounds such as 2,4-D, 2,4-DB, and Banvel.
Cotton is extremely sensitive to this group of herbicides, and
injury usually results from spray drift and/or volatilization
from treated areas such as pastures, corn, peanuts, fencerows,
forests, and roadsides. Injury can also result from contaminated
equipment used to treat cotton. The injury symptoms are quite
readily recognized. They are characterized by an abnormal elongation
of the leaf veins with a decrease in area between veins. This
results in a finger-like or okra leaf appearance accompanied
by a twisting of the stems or new growth. The severity of the
symptoms depends on the dosage received and the growth stage
of cotton.
- Methanearsonates. The herbicides MSMA and DSMA are
sold under various trade names. When used properly as directed
sprays, little or no injury occurs. However, some growers use
MSMA or DSMA over the top of cotton, and injury invariably occurs.
The extent of injury depends on the rate used, the age of the
cotton when sprayed, and weather conditions before and after
treatment. The injury can appear as a burning of the leaves,
reddening of the stems, shortening of the internodes, and dwarfing
of leaves on new growth. In some cases, leaves of new growth
may have a mottled chlorotic appearance. In severe cases, bolls
will be shaped somewhat like hickory nuts, being long and pointed
in the apex.
- Substituted ureas. Cotton herbicides such as fluometuron
(Cotoran, etc.) and diruon (Karmex, etc.) belong to this group.
Injury symptoms are characterized by chlorotic leaves. Chlorosis
may be veinal (as with diuron) or interveinal (as with fluometuron).
Usually only older leaves are affected. Minor symptoms usually
occur on a few plants in most fields even when materials are
used properly, but this does not affect the yield of cotton.
Excessive rates, improper calibration, or poor agitation can
cause more severe injury. It should be pointed out that factors
other than herbicides--such as diseases, nematodes, plant nutrient
deficiencies, and air pollution--can cause chlorosis of the leaves.
Therefore, chlorotic leaves are by no means a positive diagnosis
of herbicide injury.
- Triazines. Prometryn (Caparol, etc.) and cyanazine
(Bladex, etc.) are the only herbicides of this group currently
used in cotton. However, other members of the group such as atrazine
or simazine, commonly used on corn, sometimes get mis-applied
to cotton. These materials also cause leaf chlorosis (usually
interveinal) very similar to that caused by some of the substituted
ureas.
- Dinitroanalines. This is the most widely used group
of herbicides in cotton with probably 80 percent of the acreage
in cotton being treated with either trifluralin (Treflan, etc.)
or Prowl. Injury from these materials results from excessive
rates or improper incorporation into the soil. Injury is observed
as stunted plants resulting from damage to the root systems which
can delay fruiting and maturity.
- Imidazolinones. Herbicides in this group, including
Scepter, Pursuit, and Cadre, are toxic to cotton both from foliar
and soil activity. These herbicides inhibit the formation of
a critical amino acid (ALS) in susceptible plants causing stunting
and yellowing in the plant terminal. Most cotton injury from
these herbicides is due to carryover from an application to a
previous crop.
- Sulfonylureas. Herbicides in this group include Classic,
Accent, Ally, and Oust. They are also toxic to cotton and work
very similar to the imidazolinones. Cotton injury can occur from
carryover of sulfonylurea herbicides to cotton, but a more likely
source would be contaminated spray equipment as the sulfonylurea
herbicides are very active in low dosages. Injury symptoms are
very similar to those caused by the imidazolinones.
- Miscellaneous. Norflurazon (Zorial) and clomazone
(Command) are registered for soil application to cotton, but
can sometimes cause bleaching of foliage and purpling of the
stems on seedling cotton. Bromoxynil (Buctril) and glyphosate
(Roundup) used with genetically modified cotton varieties can
severely injure or kill regular cotton if mistakenly applied
to non-modified varieties. Bromoxynil causes a rapid burning
and desiccation of plant tissue while glyphosate injury is exhibited
as a yellowing and stunting similar to the imidazolinones and
sulfonylureas.
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Cotton Insect Infestation Report
Grower: ______________________________
County: _________________________ Date: ______________
Scout:________________________________
Phone #: _________________ Alabama Cotton Pest Mgt. Prog.
Field Name or Number |
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Field Acreage |
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Destructive Insects |
Bollworns Tobacco Budworms:
- Worms per 100 plants
- Eggs per 100 plants
- Percent damaged squares
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Fall Armyworms per 100 plants |
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Stink Bugs per 6 ft. |
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Aphids L-M-H |
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Thrips L-M-H |
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White Flies L-M-H |
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Spider Mites L-M-H |
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Plant Bugs per 100 ft.
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Percent Square Retention |
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Beneficial Insects L-M-H |
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Additional Comments |
Example: Location of Localized Infestations,
Defoliator Insects, Size of Bollworms/Fall Armyworms, Age or
Color of Eggs |
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Back to top
Summary
None of these herbicide symptoms should be confused with insect
damage. Avoid telling growers that their cotton has herbicide
damage. If you should encounter a significant amount of any of
the conditions mentioned above, bring the condition to the grower's
attention and suggest consulting the county Extension office for
assistance in diagnosing the problem.
Trade names are used only to give specific information.
The Alabama Cooperative Extension System does not endorse or guarantee
any product and does not recommend one product instead of another
that might be similar.
For more information, contact your county Extension
office. Look in your telephone directory under your county's name
to find the number.
For more information, contact your county Extension office. Visit http://www.aces.edu/counties or look in your telephone directory under your county's name to find contact information.
Issued in furtherance of Cooperative Extension work in agriculture and
home economics, Acts of May 8 and June 30, 1914, and other related
acts, in cooperation with the U.S. Department of Agriculture. The Alabama
Cooperative Extension System (Alabama A&M University and Auburn
University) offers educational programs, materials, and equal
opportunity employment to all people without regard to race, color,
national origin, religion, sex, age, veteran status, or disability.
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