B-933

IDENTIFICATION, BIOLOGY AND SAMPLING OF COTTON INSECTS

G.T. Bohmfalk, R.E. Frisbie, W.L. Sterling, R.B. Metzer and A.E. Knutson*

* Respectively, former Extension assistant, integrated pest management coordinator, professor of entomology, Extension cotton specialist and Extension agent-entomology (PM), The Texas A&M University System.


TABLE OF CONTENTS


INTRODUCTION

IDENTIFICATION, BIOLOGY, EVIDENCE OF INFESTATION AND NATURE OF DAMAGE

KEY PESTS

OCCASIONAL PESTS PREDACEOUS INSECTS AND SPIDERS INSECT PARASITISM OF COTTON PESTS

THE COTTON PLANT

CROP MONITORING (SCOUTING)

MONITORING COTTON FRUITING RATE

MANAGEMENT DECISIONS

OTHER INSECT PEST MANAGEMENT PRACTICES

INSECT IDENTIFICATION AND DAMAGE-DIAGNOSTIC KEY

ADDITIONAL BENEFICIAL INSECTS




INTRODUCTION

R.E. Frisbie

The management of insect pests is an integral part of an economic production system. It increases producers' profits and reduces the amount of environmental contamination from pesticides. Integrated pest management (IPM) is the integration of all practical pest control methods in as compatible manner as possible to maintain pest populations below the economic threshold. In a cotton production system, IPM includes combining cultural practices--appropriate variety selection, land preparation, planting dates and early stalk destruction -- frequent field scouting; biological control through conservation of natural predators, parasites and pathogens; and selective use of insecticides to keep insect and mite populations below economically damaging levels. This cotton pest management system is designed to keep inputs at a minimum while maintaining or increasing production for maximum profit.

This publication covers the identification, biology, life cycle, evidence of infestation and nature of damage of pests that attack cotton. A special section deals with recognizing predaceous insects and spiders. Crop monitoring (scouting) is stressed as a method of determining the abundance of pests and beneficial insect and spider species. The economic threshold (action level) is related to scouting procedures. Easy-to-use diagnostic keys to aid in recognizing insect damage and identifying eggs and larvae are included.

This publication is a guide to a better understanding of the cotton insect, spider and mite complex. No reference is made to specific control procedures within geographic areas of the state. The Management of Cotton Insects series is designed to provide specific management recommendations by geographic production area. Because of changing needs and constant shifts in research technology, it is recommended that information on scouting techniques, economic thresholds, appropriate pesticide use and specific cultural practices be obtained from the following: http://insects.tamu.edu/extension/publications/index.cfm

E-7 Managing Cotton Insects in the Lower Rio Grande Valley   (PDF)

E-6 Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas  (PDF)

E-5 Managing Cotton Insects in the Southern, Eastern and Blackland Areas of Texas  (PDF)


IDENTIFICATION, BIOLOGY, EVIDENCE OF
INFESTATION AND NATURE OF DAMAGE

KEY PESTS
G.T. Bohmfalk


Key pests are serious, perennially occurring, persistent pests that dominate control practices because in the absence of control their populations may cause severe economic damage. The following key pests vary in their severity and prominence by geographical location. None are key pests on a statewide basis nor in every production year.

Boll weevil - adult, eggs and larva

Boll weevil (Anthonomous grandis grandis Boheman)

Identification. The adult boll weevil is a brown to grayish-brown beetle. The body is covered with short, fine hair, giving it a fuzzy appearance. There is considerable variation in size from slightly more than 1/8 inch to almost inch in length. The boll weevil's snout is approximately half as long as its body. It is slightly curved and has chewing mouthparts on the end. Immature stages are found inside squares and bolls. The boll weevil egg is seldom seen since it is deposited inside a square or boll. The larva is a small, legless grub with a brownish head and chewing mouthparts. This grub varies in size from very small to inch in length. The pupal or "resting" stage of the boll weevil is 3/8 to inch long and cream colored with eyes and an obvious snout.

Biology. The adult boll weevil spends the winter in hibernation, called "diapause," without food and returns to cotton in the early spring the following year. Overwintering quarters usually consist of fence rows, broadleaved plant litter along creek bottoms, ditch banks and other protected, wooded areas near cotton fields. In the spring overwintered boll weevil adults concentrate in early planted fields nearest overwintering habitat where cotton is squaring. Adult boll weevils feed on tender growth in plant terminals if the young cotton does not have squares. In the early season, boll weevils colonize localized spots and do not generally invade the entire field.

The boll weevil is a pollen feeder; its survival is diminished without squaring cotton, although adult boll weevils emerging from overwintering quarters may subsist on other plants for short periods (e.g., an average of 18 days on yellow woolywhite in the Rolling Plains area). After adult weevils feed on cotton for 3 to 7 days and mate, they lay eggs in squares that have reached at least the "one-third grown stage" (approximately 1/4 inch in diameter). Egg laying may occur in smaller squares; however, sufficient feeding material is not available for a high percentage of larvae to develop to the adult stage. Late in the season eggs may be laid in small bolls, but squares are preferred.

Boll weevil life cycleIt takes the eggs 2.5 to 5 days to hatch into the grublike larva that feeds inside the square or small boll. After larval development begins the infested square turns yellow, bracts open or flare and the fruiting form falls off the plant. The larva feeds for 7 to 14 days before pupating inside the square or small boll. During the next 4 to 6 days the pupal stage changes into an adult boll weevil. The newly developed adult eats its way out of the square or small boll and feeds on other fruiting forms for about 5 days. During this time the weevil mates and females begin to lay eggs. The entire cycle takes 16 to 18 days under ideal conditions. Six or seven generations may be produced each year with each female having the capability of laying approximately 200 eggs.

Evidence of infestation. Although adult boll weevil feeding causes little damage, it indicates the presence of weevils and that egg laying will soon follow. There are distinct differences between feeding and egg-laying punctures.

As weevils feed, a small cavity is formed at the site of feeding. If a female weevil determines that the feeding site is suitable for egg laying, she enlarges the cavity slightly and inserts her ovipositor (egg-laying tube) to deposit a single egg in the cavity. When the ovipositor is withdrawn she secretes a sticky substance that covers the cavity. This sticky secretion hardens to form a wart-like protuberance that can be easily seen and felt. Feeding punctures usually have no sticky covering and therefore no wart-like protuberance.

Nature of damage. Most of the damage is due to larval development inside fruiting forms. Feeding larvae eventually cause cotton squares and small bolls to shed or damage developing lint in larger bolls. Heavily infested cotton may produce much foliage but few mature bolls.

Cotton fleahopper (Pseudatomoscelis seriatus [Reuter])

Identification. The adult cotton fleahopper is approximately 1/8 inch long. It is flat with an elongated, oval outline and prominent antennae. The body usually is yellowish-green, although it may be white or yellow with minute black hairs and spots on the upper surface. After feeding, the immature stage is pale green with prominent, often reddish eyes. Other parts of the body also may be reddish. Cotton fleahopper eggs are yellowish-white, about 1/30 of an inch long and are inserted under the bark of small stems.

Cotton fleahopper - adult, nymph and eggs

Biology. The cotton fleahopper overwinters in the egg stage, primarily in wild hosts such as woolly croton (Croton capitatus), cutleaf evening primrose (Oenothera laciniata), showy sundrops (Oenothera speciosa), wooly tidestromia (Tidestromia lanaginosa), spotted [horsemint] beebalm (Monarda punctata), lemon [horsemint] beebalm (Monarda citriodora) and silverleaf nightshade (Solanum elaeagnifolium). At 80 F., eggs hatch in about 11 days, and the young nymphs feed on tender vegetation. They usually molt five times and require 14 to 15 days to mature into the reproductive adult cotton fleahopper. Usually there are six to eight generations per year. Of these, only one to three occur in the cotton field. Early in the spring, fleahoppers build up large numbers on alternate weed hosts. As these hosts mature and become less succulent, the cotton fleahopper searches for more preferred hosts. If cotton is present, fleahoppers colonize in it and feed on leaf and fruit buds. Some fleahoppers stay in cotton fields as long as cotton plants are lush and succulent.

CottonNature of damage and evidence of infestation. The cotton fleahopper feeds on anthers of small squares and sucks sap from leaf buds. This feeding causes squares to die and turn brown, resulting in a "blasted" appearance. When fleahoppers are abundant, heavy fruit loss may occur on preflowering plants. The cotton fleahopper prefers terminal bud clusters including young leaves and tiny squares. The piercing, sucking habit of nymphs and adults interferes with normal growth patterns in cotton. Feeding punctures stimulate the plant to produce shorter main stem internodes, more nodes and spindly branches or "suckers" from the lower parts of the plant. The fleahopper injects saliva when feeding, but its effects are only local. There is no evidence that fleahoppers transmit plant diseases or toxic substances other than digestive enzymes.

Bollworm (Heliothis zea [Boddie]) and Tobacco budworm (Heliothis virescens [Fabricius])

Identification. Bollworms and tobacco budworms pass through four developmental stages--egg, larva, pupa and adult. The adult bollworm is a robust moth with a wing span and body length of approximately 1 inches. Fore wings vary from light brown or tan to reddish-brown and are Adult bollwormmarked with dark areas near the tip and a dark spot usually near the center. The hind wing of the bollworm moth is white to light tan with an irregular dark band on the outer hind margin. The adult tobacco budworm is similar but with a slightly smaller wing span and body length of about 1 1/4 inches. The fore wing of the tobacco budworm usually is light olive green with three or four light-colored, oblique bands. In the larval stages, bollworms and tobacco budworms look alike. Their size varies from very small (1/16 inch) when hatched up to 2 inches long as the larva reaches maximum size.

Adult tobacco budworm Tobacco budworm larvae have a tooth-like projection on the inside surface of the mandibles and fine short hairs on the first, second and eighth abdominal projection (tubercle) which bear a single, prominent spine. If the projection and hairs are absent, this indicates a bollworm. A microscope or hand lens is necessary to observe these characteristics.

Bollworm egg and larvaThe larval color of both species varies from a uniform light green to shades of green or brown, usually with stripes running the length of the body. It is impossible to distinguish between the two species by coloration. Bollworm and tobacco budworm eggs are similar. When recently laid, they are whitish colored and approximately the size of a pin head. Eggs are hemispherical in shape, resembling an inverted cup, with ridges running along the side from the top center to the point of attachment on the plant. They are usually deposited singly about the plant, and as they mature, usually within 2 to 5 days, they become tannish-brown. The darkening indicates the approaching hatch.

Bollworm and Tobacco Budworm life cycle

Biology. The bollworm and tobacco budworm overwinter in the pupal stage in the soil near host plants. They pupate in the upper 5 inches of the soil. With adult emergence in the early spring, they commonly complete several generations on hosts other than cotton. These alternate hosts include legumes, corn and sorghum (bollworm only) or noncrop, native vegetation.

Moths enter cotton fields and feed on plant exudates (usually nectar). Eggs require 2 to 5 days to hatch. Larvae feed on fruiting forms for 14 to 18 days. After feeding ceases, larvae burrow into soil around plants and pupate where they spend 12 to 18 days. Upon emergence as adults, moths spend 2 to 5 days feeding on nectar from nectaries before egg laying begins again. The complete life cycle may take 35 to 50 days depending on weather conditions.

Nature of damage and evidence of infestation. The first indication of bollworm or tobacco budworm infestation may be newly deposited eggs in the terminal area of cotton plants. Eggs usually are laid on the upper surface of tender foliage and other tender parts including bracts, blooms, small squares and bolls. Newly hatched larvae usually begin feeding on tender leaf surfaces and other tender vegetation before attacking fruiting forms. Smaller larvae feed on smaller fruiting forms and generally move progressively to larger fruiting forms as they grow.

Color variation in budworm and tobacco budworm larvae Bollworm egg Freshly laid bollworm egg on cotton square
Bollworm damage to square Large bollworm boll damage


Larvae tunnel into small squares and terminal buds leaving holes that range in size from very small up to the diameter of a pencil. The entry site usually is at the base of fruit. In most cases, frass or excrement is seen at the feeding site. This frass is distinguishable from that of the boll weevil because it is slightly larger and is dark brown; boll weevil frass contains silk strands and is yellow or orange.
Boll rot after bollworm damage

Feeding damages or destroys the squares, blooms and bolls. Injured squares flare and drop from plants usually within 5 to 7 days. Large larvae feed on bolls, squares and pollen in open flowers. They may even devour the contents of large bolls. Worm-damaged bolls frequently are lost to boll rot even if not eaten completely. Larvae may "top" young plants by devouring the terminal. This often delays plant growth and may cause abnormal, nonproductive growth.






OCCASIONAL PESTS

Occasional pests are those whose populations increase to damaging levels only infrequently. In general they do not cause economic loss on a yearly basis. Occasional pest flare ups are often a result of disruptions in natural control.

Beet armyworm (Spodoptera exigua [Hubner])

Identification. The adult stage of the beet armyworm has a wing span of 1 to 1 1/4 inches, and the fore wing is grayish-brown with two yellow spots near the center. The hind wing is a translucent white with narrow brown borders. The immature stage of the beet armyworm is a distinctive green larva up to 1 1/4 inch long. There is a conspicuous black dot on each side of the second body segment behind the head. The female lays masses of about 80 eggs beginning early in the spring. These eggs are covered with hairs and scales from her body.

Beet armyworm adult Beet armyworm larva Beet armyworm egg mass


Biology. The female lays an average of 500 to 600 eggs over a 4- to 10-day period. These eggs take 2 to 5 days to hatch. The larvae then feed for about 3 weeks and pass through five instars (growth stages). As small larvae they may spin a light web over the foliage. Small larvae feed in groups for several days but later spread out and become solitary feeders. After larval feeding, Beet armyworm life cycle pupation takes place in the upper 1/4 inch of the soil in a cell formed by gluing soil particles and trash together with a sticky secretion. This entire life cycle from the egg to adult requires 30 to 40 days, depending on weather conditions. Beet armyworms overwinter in the pupal stage.

Nature of damage and evidence of infestation. The most obvious indication of infestation is the characteristic egg masses coupled with defoliation by the larval feeding. Beet armyworms also feed on fruiting forms of cotton and occasionally may cause severe damage. Larvae often feed on the bracts causing little or no damage.

Beet armyworm foliage damage Brown cotton leafworm adult Brown cotton leafworm larva

Brown cotton leafworm (Acontia dacia Drucel)

Identification. The adult stage of the brown cotton leafworm is sexually dimorphic, meaning males and females do not resemble one another. The fore wing of the female is gray at the base, bordered by an irregular dark band terminated with a white line. Each wing has a conspicuous reddish-brown spot near the trailing edge. The fore wing of the male is pale gray in the basal area and is bordered by an evenly curved white line extending obliquely across the wing. Here it joins a similar transverse line that separates the black tip from the white area. The average wing span of both male and female is about 1 inch. This is slightly smaller than the cotton leafworm.

The larval stage of the brown cotton leafworm is reddish-brown mottled with white. The larva is smooth and has a protuberance on the top of the eighth abdominal segment. Eggs are shaped like a football, bluish-green and about the size of a bollworm egg. They can be distinguished from the bollworm egg by the semitransparent ribs of varying lengths and the distinctive transparent ridges, resembling a band or belt. This insect pupates on the surface or in the top 1/4 inch of the soil. The cocoon is capsule-like and made up of soil particles, plant material and silken fibers spun by the larva. Brown cotton leafworm life cycle

Biology. Eggs, laid in the spring, hatch in about 3 days. Larvae go through several growth stages during a 12-day span. The pupal stage lasts about 15 days. Therefore, the life cycle requires about 30 to 35 days. Adult moths lay eggs 3 to 4 days after emerging from the pupal case.

Nature of damage and evidence of infestation. The brown cotton leafworm is a foliage feeder. Damage in the early stage of an infestation is characterized by a buckshot pattern of holes in the leaves. Later, and under more severe attack, the plants may be defoliated completely.

Cabbage looper (Trichoplusia ni [Hubner]) Cabbage looper adult

Identification. The adult cabbage looper is a grayish brown, mottled moth approximately I inch long with a wing span of 1 inches. There is a characteristic silvery spot resembling a "V" or a figure "8" with an open end at the top near the center of the fore wing. The hind wings are pale brown but darker toward the edge of the wing. The larva, when fully developed, is about 2 inches long and light green with several white lines extending the length of the body. The larvae have three pairs of slender legs near the head and three thicker, club-shaped prolegs behind the middle toward the rear. The middle half of the body is without legs. Usually there are two light
Cabbage looper larva Foliage damage of cabbage looper
stripes on the top and one stripe on the side of the body. The body of cabbage loopers tapers to a small head. Cabbage looper eggs are light green and slightly flat. They lack the distinctive ridges of bollworm and tobacco budworm eggs. The eggs are deposited singly on the undersurface of leaves.

Biology. The cabbage looper overwinters in a cocoon and usually remains attached to the plant material upon which it has fed. Upon emergence in the early spring, adults feed for a short time and begin laying eggs. One adult moth may lay 200 to 350 eggs. The egg stage lasts 2 to 3 days. Larvae feed for 2 to 4 weeks before changing into pupae in silk cocoons attached to plants. The pupal stage lasts 12 to 14 days before adult moths emerge. The complete generation requires about 35 days.

Cabbage looper life cycle Nature of damage and evidence of infestation. Cabbage loopers are principally foliage feeders. An infestation is characterized by a buckshot or tattered appearance in the leaves. Larvae have a characteristic movement from which the name is derived. Sometimes referred to as "measuring," the larvae move about the plant by reaching out with the front part of their body, humping up the middle and pulling the rear part of their body forward. They may eat the area between leaf veins, occasionally creating a net-like appearance. Infestations may be greater along field margins. Cabbage loopers are seldom an economic pest; however, severe defoliation of cotton plants may cause problems with boll maturation. Severe defoliation before bolls mature reduces yields drastically. Any partial defoliation occurring later in the season has little effect on yield.


Cotton aphid (Aphis gossypii Glover)

Cotton aphid on underside of leaf
Sooty mold growing on honeydew excreted by cotton aphid
Identification. Both the adult cotton aphid and the immature stages are soft-bodied, sucking insects. They range from light yellow to dark green and in many cases are almost black. Early in the season they are a darker color when feeding on new growth of cotton terminals. Later in the season, when their feeding is restricted to the underside of mature leaves, they are a lighter, yellowish color and are smaller. The immature or nymphal stage looks like the adult stage, only smaller. Most adults are wingless. There are no eggs as the young are born alive. This aphid should not be confused with the cowpea aphid (Aphis craccivora Koch). The adult of the cowpea aphid is shiny black with white patches on the legs. The nymphs are ash-gray.

Biology. The biology of the cotton aphid is unique. All adults are females. These females live and produce young on growing plants year round. Aphids reproduce rapidly. One female may produce as many as 80 young females that mature within 8 to 10 days. Thus, it is possible for aphids to have as many as 50 generations per year. These generations also occur as frequently as every 5 to 7 days under optimum conditions.

Cotton aphid life cycleNature of damage and evidence of infestation. Aphids are easily observed on cotton plants. They commonly appear on the underside of leaves where they suck the sap, causing leaves to curl and sometimes shed. Cotton aphids cause leaves to curl downward and "cup under, " which is in contrast to the upward curling caused by thrips. Aphids excrete honeydew, a sticky substance easily seen on cotton plants. A black sooty mold may grow on the honeydew during periods of high humidity. Feeding aphids may cause malformed plants or even kill seedling plants. If aphid populations are high at harvest, lint may become sticky with honeydew and interfere with ginning and spinning. Aphids serve as a very important food source for natural enemies of other cotton pests.

Cotton leafworm (Alabama argillacea [Hubner])

CottonIdentification. The adult cotton leafworm is a tan to brownish moth with a few darker, wavy, transverse bars on the fore wings. There may be an olive gray or purple tinge to the coloration. The distinctive characteristics of the cotton leafworm adults are the undulating reddish lines across the front wings and the oval dark spot near the center of each fore wing. The wing span is about 1 inches. Cotton leafworm larvae are smooth, light to dark yellowish-green and marked with three narrow white stripes down the back and one along each side.

The larvae have four black dots that form a square on the top of each body segment, similar to a double four domino. Each black spot has a black spine, and the center is surrounded with a white ring. This gives it the domino characteristic. The size varies from very small to 1 inch in length. Larvae are pale when small and change to a brighter color as they mature. Eggs of the cotton leafworm usually are seen on the underside of leaves. They are bluish-green when first laid, flat and barely as large as the head of a pin.

Biology. The cotton leafworm is a tropical species and does not overwinter in the U.S. In the spring, adult moths fly in from the tropics or are blown in on prevailing winds. They begin laying their eggs on cotton leaves. These eggs are scattered on the underside of the leaves and laid singly. Eggs hatch within 3 days and the young larvae begin feeding. Larvae pass through five to six growth stages per generation, each a different length. During optimum conditions and in mid-summer the larval stage lasts approximately 15 days. The larvae of cotton leafworms web up with a boll or roll of leaves forming flimsy cocoons for protection just before pupation. Pupation, which occurs on the cotton plant, takes approximately 6 to 10 days. Newly emerged adults lay eggs within 2 to 4 days.

Cotton leafworm life cycleNature of damage and evidence of infestation. Feeding patterns of cotton leafworms are characteristic because they feed on the underside of leaves between the veins, skeletonizing them. The skeletonizing of leaves causes a reduction in photosynthetic potential. Although this insect is essentially a leaf feeder, it can attack squares and small bolls. The cotton leafworm in Texas is a late-season pest that often aids defoliation just before harvest.




Cotton leafworm larva Newly laid cotton leafworm egg Cotton leafworm larva forming cocoon
Skeletonizing of leaf by cotton leafworm Small, white cotton leafperforator adult Cotton leafperforator larva

Cotton leafperforator (Bucculatrix thurberiella Busck)

Identification. The adult cotton leafperforator is a small, slender, usually white moth with black markings on the fore wings. The wing span and body length are approximately 2/5 to inch. The larva is a dull amber green with two rows of black spots and distinct white projections (tubercles) on its back. The larva reaches a maximum length of inch. The pupa is a cocoon of silk-like material on the stalks of cotton plants. These pupal cocoons are white, approximately inch in length and arranged longitudinally on the plant. Eggs usually are laid singly on cotton leaves.

Biology and evidence of infestation. After eggs hatch, early instar larvae make a winding, randomly patterned mine in leaves. The larvae feed in the mines through the third instar. At the fourth instar they emerge from the mine as free feeders. Damage from these free-feeding larvae skeletonizes the leaf. Cotton leafperforators have a characteristic horseshoe-shaped stage that marks the time between the fourth and fifth instar larva. This resting stage is in the form of a small, grayish horseshoe and is obvious on the underside of the leaf. When cotton leafperforator larvae emerge from the horseshoe stage they continue to feed freely. Mature larvae spin a fine web, drop to the ground and move along the ground to the base of cotton or other plants in the area. There the characteristic slender, ribbed, white cocoon is constructed. The cotton leafperforator is most frequently a problem in hot, dry climates. Cotton leafperforator life cycle

Nature of damage. The main damage done by the cotton leafperforator involves interference with normal boll maturation. Severe infestations halt normal growth and respiration of the cotton plant and effectively stop the maturing process. Heavy populations are commonly associated with multiple insecticide applications that destroy parasites and predators. Fortunately, infestations usually occur late in the season when the crop is mature.





Cotton leafpeforator damage Cotton leafpeforator larva feeding Slender white cocoon of the cotton leafpeforator
Cotton square borer adultCotton square borer larva

Cotton square borer (Strymon melinus [Hubner])

Identification. The adult cotton square borer is a slate or bluish-gray butterfly. It has two large black spots on the wings with smaller reddish-orange spots above these at the back edge of the hind wing. There are usually two or three thin tails on the hind wing. The underside of the wings is lighter gray with a white streak along the edge. The wing spread of the cotton square borer adult is approximately 1 inch. The larval stage is a velvety, light green, slug-shaped worm. The body is covered by a succession of oblique lines running the width of the body segments. Cotton square borer eggs are pale green and laid singly on plants. Cotton square borer life cycle

Biology. The adult begins laying eggs early in the spring. The eggs take approximately 6 days to hatch; then the small larvae feed on cotton squares for approximately 20 days. After the feeding period the insect spends about 10 days in the pupal stage.

Nature of damage and evidence of infestation. Presence of adult butterflies usually is the first indication of cotton square borer activity. However, hollowed out squares with almost perfectly round entrance/exit holes also may be observed. Unlike bollworm or tobacco budworm damage, there is no frass present with cotton square borer damage.



Cotton stainer (Dysdercus suterellus [Herrick-Schaffer])

Cotton strainer adultIdentification. The adult cotton stainer is a "true bug" with piercing, sucking mouthparts. The head and pronotum are bright red; the remainder of the body is dark brown crossed with pale yellow lines. The length is inch or slightly longer. Immature stages are smaller but resemble adults without wings. Cotton stainer eggs are small, pale and laid singly on cotton plants or dropped on the ground near cotton plants.

Biology. Eggs hatch in 5 to 8 days. There are five instars in the immature stage which lasts about 21 to 35 days. The first instar immatures are usually found congregating near the egg shell after emergence. The second and third instars feed gregariously on the bolls. Later instars wander freely over the plant.

Nature of damage. The cotton stainer is mainly a pest of long staple cotton. It damages developing bolls by puncturing seeds and causing plant sap to exude from the feeding site. The plant sap stains the lint an indelible yellow color. Feeding by the cotton stainer also interferes with the bolls' natural development.

Cutworms (Agrotis spp.)

Cutworm adult Cutworm larva and damage
Identification. The adult cutworm is a brown to gray robust moth. The wing span varies from I to 1 inches. Several species infest cotton. Cutworm larvae characteristically curl up into a C-shaped posture and regurgitate readily when disturbed. The larvae are often shiny or glossy and always have four pairs of prolegs.

Biology. Most cutworms overwinter in the larval stage, but some overwinter as pupae or adults. The eggs are laid on grass or soil in low spots of the field. They normally hatch in 2 to 5 days. Cutworms life cycle The average time of larval feeding is 2 to 3 weeks. The pupal stage remains in the soil for 7 to 8 days. About 35 days normally are required to complete a generation.

Nature of damage and evidence of infestation. Cutworms usually cut off plant stems at the soil surface. Stand reduction may be more visible in field margins and low lying weedy areas. Some cutworm species climb up plants and feed on leaves. Cutworm damage can be severe enough to require replanting on rare occasions.






Fall armyworm (Spodoptera frugiperda [J.E. Smith])

Fall armyworm larva Identification. The adult fall armyworm is a dark brownish-gray, mottled moth with oblique markings near the center of the fore wing. There is an irregular white or gray patch near the wing tip. Female moths are darker than males. The hindwing is white in females with a pearly or pink luster and a brown border. The wing span of the fall armyworm is approximately 1 inches. The larva of the fall armyworm, when newly hatched, is white with a black head. As feeding progresses, the larva becomes darker. Young fall armyworms often curl up on a leaf or suspend from a silken thread. As the larvae mature they turn greenish-brown with a white line below the top of the back, usually a brownish-black stripe above the midline and a pale stripe with a reddish-brown tinge below. Mature larvae are about 1 inches long. There is a prominent white inverted "Y" on the front of the head. Fall armyworm larvae can be distinguished from beet armyworms by the presence of black hairs on the body. Fall armyworm eggs are similar to those of the beet armyworm. They are laid in masses of 50 to 100 and covered with hairs and scales from the female's body.

Biology. The fall armyworm is another tropical insect which is apparently unable to overwinter in the United States except during mild winters. In the early spring swarms of moths are blown up or fly northward from tropical areas. Approximately 3 to 5 days are required for the eggs to hatch. Developmental time of the larval stage takes 2 weeks to a month. Pupation occurs in the ground near the cotton plant and usually requires 1 to 2 weeks. The adult begins laying eggs after 3 or 4 days and lays about 150 eggs a day for 8 to 10 days.

Fall armyworm life cycle Nature of damage and evidence of infestation. When abundant, they generally eat all available foliage and then crawl in armies to adjoining fields. Fall armyworms are general feeders and do not confine themselves to cotton.

Fall armyworm populations can build up large numbers in cotton fields, and defoliation may be quite severe on rare occasions. The greatest damage comes from the topping of plants. Branches may be cut off and sometimes the stalks may almost be completely severed a foot from the top. They also tend to feed on squares, blooms and bolls on the flower part of the plant. Several worms may be found on individual plants. They are an occasional cotton pest where grasses grow in or near cotton fields.


Grasshoppers -- Lubber grasshopper (Brachystola magna [Girard]); Differential grasshopper (Melanoplus spp.)

Grasshopper feeding Grasshopper damage

Identification. Adult grasshoppers vary in appearance, but all have well developed back legs for jumping. The immature stage is similar to the adult but does not have wings. Grasshopper eggs are laid in the soil in a cemented mass or pod. Depending on the species, there may be 8 to 25 eggs in each pod. These pods usually are distinctive and are used in species identification.

Biology. The biology of the different grasshoppers varies considerably. However, in most species the female lays eggs in the soil where overwintering takes place. Some species overwinter as Grasshopper life cycle partially grown nymphs or as adults. Upon hatching in the early spring, grasshoppers usually require 40 to 60 days of feeding before reaching reproductive maturity. Seldom is there more than one generation per year.

Nature of damage. Grasshoppers may become problems in cotton fields when wild or cultivated host plants are depleted near fields. When infestations are heavy, grasshoppers cause severe defoliation by feeding on foliage and tender plant parts. Their damage usually is confined to areas along field margins where alternate host plants are near.


Tarnished plant bug (Lygus lineolaris P. de Beav.)
Tarnished plant bug adult and nymph
Tarnished plant bug adult

Identification. Adult tarnished plant bugs are about 1/4 inch long and approximately half that wide. They are flat and have an oval outline. They are similar to cotton fleahoppers in shape; however, they usually are about two to three times larger than the cotton fleahopper. They are generally brown in color with splotches of white, yellow and reddish-brown. Along the side of the body on the hind part of the wing there is a clear, black-tipped triangle. This description varies from the lygus bug, typically found in West Texas, in that its color ranges from pale green to yellowish brown. There is a conspicuous light-colored triangle on the back of the Lygus bug (Lygus hesperus Knight) between the wings. When first hatched, tarnished plant bug nymphs are pale green and have an orange spot in the middle of the abdomen. After feeding begins, nymphs become darker green and black spots become evident on the body segment (thorax) between the head and abdomen. The whitish egg is slightly curved, elongated and has a lid on its tip.

Biology. In most areas tarnished plant bugs overwinter as adults. Mature adults lay eggs in the cotton plants; these hatch in about 8 days. The immature nymphal stage develops in approximately 11 days. Each generation is completed in 20 to 30 days in the summer, and there may be more than one generation per year.

Nature of damage and evidence of infestation. Like cotton fleahoppers, most tarnished plant bugs occur on other host plants in areas surrounding cotton fields. They feed by inserting their Tarnished plant bug life cycle mouthparts into the tender plant parts and sucking sap. Feeding on squares and small bolls usually causes fruit shed. The most important period of plant susceptibility is during the first 3 weeks of squaring with the first week being the most critical. During heavy infestations fruit removal can be excessive and of economic importance. Occasionally, damaged squares and bolls do not shed. Although squares may bloom, floral parts are damaged and show evidence of feeding. If an injured boll does not shed, it opens abnormally and may have lint damage.







Omnivorous leafroller (Platynota stultana Walsingham)

Identification. The adult stage of the omnivorous leafroller is a small moth approximately to 3/5 inch long. The fore wing has a dark brown inner half and a yellowish-brown outer half. Mouthparts that extend in front of the head give the appearance of a beak. The immature stage is a yellowish-white caterpillar with a brown head and shield behind the head. As the larva matures the coloring changes to yellowish-green or brownish-green with a broad transparent stripe down the top of the back. The larva is approximately 3/5 inch long. The green eggs are laid in flat clusters overlapping one another like fish scales. The egg mass is cemented to the plant with a secretion from the female's reproductive glands.
Omnivorous leafroller life cycle

Biology and evidence of infestation. The adult female omnivorous leafroller may lay more than 300 eggs during her life span. These eggs take only a few days to hatch. The dark-headed larvae begin making silken ladders on which they move about and feed. The larva has a peculiar habit of concealing itself by rolling a leaf around its body. Some larvae develop completely in a single leaf roll, while others may build several. After about 25 days of feeding pupation takes place within the leaf roll. The adult emerges about 5 days later.



Pink bollworm (Pectinophora gossypiella [Saunders])

Pink bollworm larva Pink bollworm exit holes left before pupation Pink bollworm lint damage

Identification. The adult pink bollworm is a inch grayish-brown moth with a 2/5 inch wing span. When it rests, the moth's wings are folded close to the body. These wings are covered with poorly defined black spots and have blackish tips with a broad band near the tip. Wing margins are fringed with hairs. The immature pink bollworm is a small larva with a yellowish brown head. It may be as long as inch just before pupation. Young larvae are white and turn pink with age. The pink coloration occurs in dark transverse bands running across or covering the body. Pink bollworm eggs are greenish-white and are laid on the stems and squares and occasionally on terminal buds. They are most often found between the calyx and boll wall. Eggs are usually deposited singly.

Biology. Eggs normally hatch within 4 to 5 days. Developing larvae bore into and feed on the developing flower or into a boll to feed on the seed. Larvae feed for 10 to 14 days. They usually leave the fruit and pupate in the soil, taking about 8 days to transform into an adult. In late summer and fall many larvae do not pupate immediately upon completion of the feeding period but remain inside the boll. These are the overwintering stages that give rise to the first generation the following season. Overwintering usually takes place in seed inside bolls or inside two hollowed out seeds with a pupal case connecting them. These "double seeds" are found when cotton is ginned.

Pink bollworm life cycle Nature of damage and evidence of infestation. Early in the season, infested squares continue growing and producing blooms. These infested blooms may have the petals tied together with silken threads, commonly termed "rosetted." The rosetted flowers do not open normally. After bolls are present they become the preferred egg-laying site. The developing larvae tunnel through the boll wall until they reach the lint. They cut through the lint fiber as they move from seed to seed. The burrowing activity stains lint; destroys fibers; and reduces seed weight, vitality and oil content. Pink bollworms cut holes in boll walls as they leave bolls for pupation. These holes may become infected with boll-rotting organisms. During severe infestation, many bolls that might otherwise have been harvested are rendered unpickable.

Saltmarsh caterpillar (Estigmene acrea [Drury])

Saltmarsh caterpillar adult Saltmarsh caterpillar egg masses
Identification. The adult saltmarsh caterpillar is a large, light-colored moth. The abdomen usually is orange to yellow and may have black spots on the top. Male and female moths differ in the way their wings are colored. In the male the fore wing is white and the hind wing is orange to yellowish. In the female both wings are snowy white on the top and yellow below. The wing surfaces of both sexes are marked with variable black spots. The wing span usually is 1 to 2 inches. The larval stage of the saltmarsh caterpillar is sometimes called a "wooly bear," because the body is covered with long hairs giving it a wooly appearance. These larvae are gray to black to reddish brown with a dark head. The full sized larva reaches a length of 2 1/4 inches.

Saltmarsh caterpillar life cycle Biology. The saltmarsh caterpillar overwinters under plant debris in the pupal stage inside a fragile, silken cocoon heavily covered with interwoven hairs from the caterpillar's body. Upon emergence in the early spring, the female lays as many as 1,000 spherically shaped eggs in patches on the underside of host plant leaves. Newly hatched saltmarsh caterpillar larvae are gregarious. They feed in large numbers on the bottom side of leaves. As the larvae mature they disperse and feed singly. The larval stage requires 30 to 48 days for completion; pupation may take up to 14 days. There usually are two to five generations per year.

Nature of damage and evidence of infestation. This insect usually is a problem on the edges of fields and in areas where alternate host plants are available. These pests can be severe defoliators when present in large numbers. Saltmarsh caterpillars may migrate in mas from one field to another like armyworms.

Spider mites (Tetranychus spp.)

Spider mites on underside of leaf Identification. Spider mites are not insects. They have eight legs in the adult stage instead of the six which is characteristic of insects. The adults are so small they can barely be seen with the naked eye. They are usually red, but may be green, orange or straw colored. Casually observed, spider mites often look like dust particles on the underside of leaves.

Biology. Although spider mites attacking cotton are really a complex of several genera and species, they all have similar life histories and biology. Spider mites pass through egg, larval, nymphal and adult stages. They overwinter in the adult female stage in protected vegetation near fields. The female lays her eggs on the underside of leaves in early spring. Eggs hatch in 1 to 3 days. Freshly hatched larvae have only six legs and are transparent. They feed for 2 to 3 days before molting (shedding their skin) and developing into eight-legged nymphal mites. Nymphs feed for 5 to 6 days before molting into eight-legged adults. Adults feed for 1 to 3 days before laying eggs. The entire life cycle requires only 6 or 7 days under optimum conditions and 11 days under normal field conditions. Spider mites have an unusual life history in that fertilized eggs produce females and unfertilized eggs hatch into males.

Spider mite life cycle Nature of damage and evidence of infestation. Spider mite infestations should be suspected when small, yellow spots appear on the upper surface of cotton leaves. This stippled discoloration is typical of early feeding stages. These yellow areas often result in leaf reddening as mite feeding continues. Large numbers of mites cause leaves to die and complete defoliation can occur. The lower surface of an infested leaf usually is covered with a fine web and cast skins. Live spider mites can be observed crawling beneath the web on the underside of the leaf surface. Spider mites cause more harm to cotton plants during hot, dry weather and usually attack cotton in the latter part of the season. Mites damage cotton by feeding on the sap of leaves, stems and squares. Since they suck sap and chlorophyll from the leaves, this reduces the photosynthetic area and interferes with normal maturation of the cotton plant. Spider mite infestations generally begin on the edge of fields and then spread through the field. They frequently are a problem following insecticide applications which kill their natural enemies.

Evidence of spider mites Leaf reddening caused by spider mite feeding

Stink bugs (Acrosternum hilare [Say]) and (Chlorochroa ligata [Say])

Green stinkbug adult Identification. Two species of stink bugs are typically found in Texas cotton and may cause problems. The green stink bug (Acrosternum hilare [Say]) and the conchuela stink bug (Chlorochroa ligata [Say]) are most often involved. The adult stages of these two stink bugs are similar. They are shield-shaped, flat and vary in size around inch in length. The green stink bug is bright green, while the conchuela stink bug is dark brown to black with a red border and a red spot on the tip of the abdomen. The immature stage of the stink bug is similar to the adult but lacks wings. Stink bug eggs have a distinctive barrel shape and usually are laid in clusters on stems and leaves. These egg masses resemble many barrels lined up in rows.

Biology. The biology of these two species follows the same pattern. Eggs are laid on the host plant and require only a few days to hatch. When climatic conditions are favorable, a generation of these insects may be completed in about 6 weeks.

Stink bug life cycle Nature of damage and evidence of infestation. Stink bugs seldom develop in large numbers on cotton. They feed by inserting their long, piercing mouthparts and sucking out the plant juices thereby injuring squares and bolls. This may cause small bolls to fall from the plants. Although larger bolls commonly remain on the plant, feeding injury results in hardened, dry locks. At each feeding site there is a hardened spot. Lint beneath the feeding spot may be stained or reduced in grade. Boll-rotting organisms also are associated with the feeding of these insects. In Texas stink bugs rarely occur in damaging numbers. They are most likely to be found in damaging numbers late in the season.


Conchuela stink bug nymph Stinkbug eggs Stinkbug feeding


Thrips (Thrips spp.) and (Frankliniella spp.)
Thrips adult Thrips damage on leaves Severe thrips damage

Identification. Thrips are minute, slender, agile insects. They rarely exceed 1/15 inch in length and usually are yellowish-brown, black, tan or sometimes orange. Their mouthparts are cone-shaped, and their wings are narrow and fringed with hairs.

Thrips life cycle Biology. Thrips appear on growing plants throughout the year in most areas. Eggs, inserted into the plant tissue by the female's sharp egg-laying tube (ovipositor), hatch in about 6 days. There are two larval stages that require about 6 days for completion.

The prepupal and pupal stages require an additional 4 days. Egg to adult development requires about 16 days. The average life span of a mated female is about 35 days. Fifty or more eggs may be produced. Thrips can reproduce without mating. Mated females produce both males and females while unmated females produce only males. Nature of damage and evidence of infestation. Thrips are early season pests of seedling cotton. They may be a problem under cool, wet conditions when plant growth is slowed. They may be especially numerous in cotton grown near maturing small grains. Thrips damage cotton leaves and terminal buds. Their feeding ruptures cells which cause stunted plants and crinkled leaves that curl upward. During severe infestations terminal buds may be destroyed, causing excessive branching of the plants and delaying plant growth. Also, the cotyledonary leaves take on a silvery appearance, sometimes termed "bronzing.

Figure 1. Growth stages of the cotton plant

Whiteflies (Bemesia tabaci [Gennadius])

Adult whitefly and nymphs Whiteflies on underside of leaf
Identification. The adult whitefly is about 1/16 inch long and snowy white. These moth-like insects are very active and fly readily when disturbed. The immature stage is a flat, scale-like insect usually about 1/30 inch long. The immatures usually are found on the underside of leaves. Whitefly eggs are only visible under magnification.

Biology. Whiteflies are active throughout the year on alternate hosts. Adults mate immediately after emerging from pupae. Eggs are laid on fully opened leaves in the terminal. These eggs require about 5 to 6 days to hatch. The nymphs, also called crawlers, move short distances, but after they insert their mouthparts into the leaves they become immobile. They feed for 5 or 6 Whitefly life cycle days during the first three growth stages. Another 5 or 6 days are spent in a pseudo-pupal stage where no feeding occurs for the last 2 days. After this stage the adult emerges ready to produce eggs. The adult female lays an average of seven eggs a day for 3 weeks. Peak whitefly numbers usually occur early in the season and during high humidity periods.

Evidence of infestation and nature of damage. These tiny snow white insects are easily observable flying about the cotton plant. They excrete honeydew much like aphids. Infested leaves lack vigor, wilt and may turn yellow.





Yellow-striped armyworm (Spodoptera ornithogalli [Guenee])

Yellow-striped armyworm adult Yellow-striped armyworm larva

Identification. The adult yellow-striped armyworm is a large moth with a wing spread of 1 to 1 3/4 inches. The fore wing is blackish-brown, occasionally with a reddish tint, or may be yellowish-brown with oblique yellow markings near the center. There may be bluish-gray markings at the apex and the hind angle of the fore wing. The wing veins usually are lighter colored. Hind wings usually are irridescent white with a narrow brown border. The larval stage is a smooth caterpillar with scattered short hairs. As with other armyworms found in cotton, the inverted "Y" on the front of the head is prominent. The yellow-striped armyworm has a pair of black, triangular spots below the top surface on each segment except those between the head and the abdomen. There are yellowish-brown or occasionally orange stripes with white lines along each side. These yellow lines give the yellow-striped armyworm its name. Eggs are laid in masses on leaves and are covered with hairs and scales from the female's body.

Yellow-striped armyworm life cycle Biology. This species overwinters in the pupal stage. After emerging in early spring, the female feeds for a couple of days before laying eggs. Eggs hatch in about 6 days. The larval stage takes approximately 20 days to complete. Pupation usually takes about 14 days during the summer. An entire life cycle from egg to adult requires 35 to 45 days.

Nature of damage and evidence of infestation. The yellow-striped armyworm is a day-feeding insect. The brightly colored larvae are easy to recognize. They prefer foliage as the feeding site. They also bore into squares and bolls. They are general feeders and infrequent cotton pests, although when alternate hosts are not available they can defoliate cotton and damage the fruiting forms.


PREDACEOUS INSECTS AND SPIDERS

W.L. Sterling

In Texas, native predaceous insects and spiders are the dominant biological control agents of the bollworm (Heliothis zea [Boddie]) and the tobacco budworm (H. virescens [Fabricius]). Native parasites are also valuable natural enemies. Other predators such as birds, lizards, snakes, toads, frogs, mice, skunks, armadillos, etc., also prey on these insect pests, but their dependability and efficiency generally are much lower than that of parasites, predaceous insects and spiders in cotton fields.

Native biological control organisms, along with other factors such as heat, cold, moisture, etc., often maintain cotton pests below numbers that cause economic crop losses. About 60 percent of the cotton in Texas is grown without requiring chemical insecticides, thus dependence is entirely on biological and physical control. Researchers are working to establish economic thresholds (action levels based on pest densities at which protective action is needed to prevent unacceptable losses) and to establish predator densities at which no action (inaction levels) is needed because the predators are sufficient to maintain pests below the economic threshold. It is essential to know which predators are most abundant and efficient and when they move to or from the field. A knowledge of predator effectiveness against individual pest species also is needed.

Predator densities and seasonal changes in populations presented in the following discussion are based on levels observed in East Texas cotton fields where broad spectrum insecticides are not used directly on the crop or do not drift into the field. The time of peak predator densities and average densities varies across Texas depending on prey availability, growth stage of the cotton plant, predator distributions and many other factors. The species and number may vary in some years and in some places.

The choice of predators for this discussion was based on their relative abundance in cotton and their importance as egg and small larval predators of bollworms or tobacco budworms. These predators often eat eggs and small worms before they develop into large worms that cause crop losses. In general, small predators feed on small prey such as eggs and small larvae, and larger predators kill large worms. Thus, identification of small, immature insect and spider predators, as well as adults, is important in pest management.

Most predators in cotton fields are general feeders that do not depend on a single pest species for food. Thus, if one prey species becomes scarce, predators switch to another prey or may even resort to plant juices or nectar to survive. A complex of predator species can coexist and bring stability to the system. As any one pest species increases, bringing it out of balance with the system, predators switch to this new food source and again bring the pest into equilibrium.

Native predators are of great economic benefit to the cotton farmer. They voluntarily enter the cotton field, are self-multiplying and are completely free of cost.

More than 600 insect and spider predator species have been recorded in cotton fields. The 16 most important species are included in this publication.

Insects

The abundance and importance of insect predators vary considerably from year to year and from place to place. In any particular locality certain insect predators not mentioned here may be dominant. However, current evidence suggests the following eight insects play a dominant role in regulating bollworms and tobacco budworms in many cotton fields.

Minute pirate bugs (Orius spp.)

Minute pirate bug feeding Two species of pirate bugs are found on cotton in Texas. In eastern Texas the insidious flower bug (Orius insidiosus [Say]) is often the dominant species. In West Texas and the Lower Rio Grande Valley it is often replaced by the minute pirate bug (Orius tristicolor [White]). Both species are black and white and measure less than 1/8 inch.

Pirate bugs usually are one of the most abundant cotton predators averaging three per meter (40 inches) of row with peaks of five to 10 per meter of row in mid-July in East Texas. They enter the cotton field very early in the season, reaching a spring peak in June or July and a fall peak in September. They feed on aphids, thrips, whiteflies, mites and bollworm-budworm eggs and small larvae. Reproduction occurs in cotton. The orange pirate bug nymphs also are predaceous.

When bollworm or tobacco budworm eggs are plentiful, pirate bugs eat about one egg per day. They also kill and consume about one or two small worms every 2 days.

Bigeyed bugs (Geocoris spp.)

Bigeyed bug nymph feeding Several species of bigeyed bugs are found in Texas cotton; however, the two most abundant species are G. punctipes [Say]), a large grey species, and G. uliginosus [Say]), a small black species. All bigeyed bugs found on cotton have distinctively broad heads, large conspicuous eyes and range in length from 1/8 to 1/4 inch.

In East Texas, bigeyed bugs peak in mid-July at two to five per meter of row while averaging about one per meter over the season. They enter cotton fields as soon as prey is available and remain throughout the growing season. Both adults and nymphs feed on mites, whiteflies, thrips, Lygus bugs and fleahoppers while consuming about two bollworm or tobacco budworm eggs per day under field conditions. They also may feed on up to one small bollworm or tobacco budworm larva per day. They readily feed on various seeds and suck plant juices but are not considered harmful to the plant.

Reproduction takes place in the cotton field. Nymphs of G. punctipes are gray while G.uliginosus nymphs are solid black.

Ants (Solenopsis spp.)

Red impoted fire ant attacking a bollworm Many species of predaceous ants may be found on unsprayed cotton in Texas. Probably the most important are the fire ants (Solenopsis species). In areas inhabited by the red imported fire ant (Solenopsis invicta [Buren]), this ant specie often makes up 98 percent of all ants present. In West and South Texas where imported fire ants are not found, other species such as the tropical fire ant (S. geminata [Fabricius]) or in North Texas the southern fire ant (S. xyloni [McCook]) are important predators. Worker ants, generally found in cotton fields, are about 1/8 inch long, dark red to black, wingless and have a two-segmented waist (i.e., abdominal stalk).

Ants enter cotton when aphids start producing honeydew and may reach densities of 10 to 20 ants per meter of row while averaging about eight. Young queens colonize cotton fields after rains. Ant numbers usually peak in late June and again in early August. Each ant may take about 0.3 bollworm or tobacco budworm eggs and 0.1 small worms per day. Since ants can hunt in packs, they can capture rather large prey and are excellent predators of immature boll weevils. Fire ants are relatively ineffective predators of most other predaceous insects and spiders.

Lady beetles (Hippodamia spp.)

Convergent lady beetle feeding Of the many large lady beetles found in cotton, the most numerous and effective is the convergent lady beetle (Hippodamia convergens [Guerin-Meneville]). The adult generally is orange with 12 black spots on the wing covers (elytra). The orange and black larva also is predaceous. Lady beetle populations are related to aphid numbers, so lady beetles are most abundant when aphid populations are high.

Although large lady beetles are not as abundant as some of the other predators, they apparently find and eat more bollworm-budworm eggs per individual. Under field conditions they are capable of finding and eating about 12 eggs per day. They also attack small-to-medium bollworm or budworm larvae.

Cotton fleahoppers (Pseudatomoscelis seriatus [Reuter])

Cotton fleahopper feeding on bollworm egg This insect is considered an important cotton pest because its feeding causes small squares to shed. However, the fleahopper also should be considered a predator on bollworm or tobacco budworm eggs. Under field conditions the fleahopper may eat about one bollworm or tobacco budworm egg per day.

Fleahopper adults enter the cotton field when plants are very small. As an example in East Texas, their numbers peak in May or June and again in September. In some locations they may average about seven adults and nymphs per meter with peaks of 20 per meter. Since fleahoppers generally are considered pests only on preflowering cotton, they might be considered beneficial after flowering. Both adults and nymphs are predaceous but also serve as food for many other predators.

Green lacewings (Chrysopa spp.)

Green lacewing larva feeding Although many species of green lacewings are present in cotton fields, the most abundant are the common green lacewing (Chrysopa carnea [Stephens]) and the green lacewing (Chrysopa rufilabris [Burmeister]). Adults are about to 3/4 inch long, and are yellowish-green with golden eyes and large, delicate, netted wings. The larvae grow to a maximum length of 3/8 inch, are alligator-shaped, have long sickle-shaped jaws and are mottled brown. Eggs are deposited on the end of long delicate stalks.

In East Texas green lacewings peak during mid-July at about one per meter of row, averaging one per 5 meters. Green lacewings often are more abundant in central and western parts of Texas. Movement begins in February or March, reaching a spring peak in May and a fall peak in September.

Common green lacewing adults are not predaceous, but the immatures feed on aphids, spider mites, whiteflies and bollworm or tobacco budworm larvae and may consume about one egg or small worm every 2 days.

Damsel bugs (Nabis spp.)

Damsel bug feeding on bollworm Several species of damsel bugs are found on Texas cotton. One of the most abundant species is the pale damsel bug (Nabis capsiformis [Germar]). Adult damsel bugs are slender with relatively long legs. They range from about 3/8 to inch long and are tan to reddish-brown. The body tapers toward the head which is armed with a long beak. Damsel bug nymphs resemble adults but are smaller and lack wings.

In East Texas, damsel bugs usually are found at densities of less than one per 10 meters of row with occasional peaks of about two per meter between mid-June and mid-August. However, in some years and in some areas they reach densities of up to 10 per meter.

Damsel bugs feed on bollworm-budworm eggs and larvae as well as aphids, fleahoppers, Lygus bugs, leafhoppers and spider mites. They also prey on other predators such as minute pirate bugs and bigeyed bugs.

Assassin bugs (Zelus and Sinea spp.)

Leafhopper assassin bug feeding on bollworm The most abundant assassin bugs in cotton are the leafhopper assassin bug (Zelus renardii [Kolenati]) and the spined assassin bug (Sinea diadema [Fabricius]). The leafhopper assassin bug adults are about inch long and of moderate to slender build. They are various colors including red, brown and yellowish green. The elongated narrow head is armed with a strong beak. The nymph resembles the adult but is smaller and wingless.

The spined assassin bug also is about inch long and is almost uniformly dark brown to dull reddish brown. Abdomen margins are expanded and flat with a pale spot on the rear margin of each segment. The front legs are covered with spines. Nymphs resemble the adults but are wingless and distinctly sway-backed.

Assassin bugs peak at about one per 2 meters of row during July but average only seven per 100 meters during the season. Dispersal reaches a peak during the fall. They are predators of cotton fleahoppers and bollworm-budworm eggs and larvae and are one of the few predators that can readily capture and consume an adult boll weevil, as well as larger Heliothis larvae.

Spiders

Spiders are important in regulating pest insects but are not numerous enough to control excessive numbers that occur during major outbreaks. Along with other mortality agents, spiders often keep pests below densities that cause unacceptable cotton losses.

Striped lynx (Oxyopes salticus [Hentz])

Striped lynx spider The striped Lynx is a hunting spider and builds no web. It can be identified in the field by its habit of running rapidly and erratically and jumping. It is a brownish colored spider about 1/4 to 3/8 inch long with four longitudinal grey stripes behind the eyes on the front half (the carapace). Two black lines extend down the face and the jaws (chelicerae). Legs have large spines and the abdomen tapers to a point. Immatures resemble adults but are smaller.

This spider usually is the most abundant spider in East Texas cotton fields, averaging more than one per 2 meters of row with peaks of two per meter. Numbers of striped Lynx build throughout the growing season, peaking in September. They reproduce throughout the growing season so immature spiders are moving into cotton fields almost continuously. Immatures often are abundant on green vegetation during the winter.

The striped Lynx preys on cotton fleahoppers, Lygus bugs and small bollworm-budworm larvae.They do not readily prey on bollworm-budworm eggs, but in Arkansas they account for 11 to 14 percent of all arthropod predation on second-instar bollworm larvae. They may consume about one egg or small larva every 2 days.

Celer crab spider (Misumenops celer [Hentz])

Celer crab spider The celer crab spider is also a hunting spider, does not weave a web and usually is found in plant terminals. The four front legs are longer than the four rear legs, and there usually are two longitudinal stripes behind the eyes on the carapace. Also, the rear half of the abdomen often has a "V" shaped mark pointing toward the rear. Adults reach a length of about 1/4 inch. They are yellow, green or white with reddish markings. Immature stages resemble adults but are smaller. These crab spiders enter the cotton field early but reach a peak density of about one per meter of row in October and November in East Texas. The seasonal average density is about one per 10 meters of row.

Celer crab spiders feed on cotton fleahoppers, Lygus bugs and a wide range of other insects, including bollworm-budworm eggs and worms; they may consume about one egg every 2 days and one worm per day.

Winter spider (Chiracanthium inclusum [Hentz])

Winter spider feeding on bollworm The winter spider is found during the day in silken nests under leaves or bracts of squares. These hunting spiders do not spin a typical web and hunt primarily at night. The adult is about 1/3 inch long and cream to pale green with dark brown chelicerae. A faint, median longitudinal band is found on the front half of the abdomen. Young spiders resemble the adults.

Peak numbers of up to one per meter of row may be found during July and August. Average densities of about one per 10 meters are found throughout the season. Immatures float through the air on webs (ballooning) from March to December but most commonly from August through November.

Immatures of the winter spider feed on bollworm-budworm eggs, possibly taking 14 per day when eggs are abundant. A second instar winter spider consumes an average of 3 first instar bollworms in I hours in the laboratory and about three per day in the field. They prefer bollworms and other species of worms and flies but also eat bugs, grasshoppers and beetles.

Star-bellied orb weaver (Acanthepeira stellata [Walckenaer])

Star-bellied orb weaver Large webs spun between cotton rows often are made by the star-bellied orb weaver, frequently the most abundant web-spinner in cotton. When the web is found, the spider may be located under a leaf to which one of the foundation lines of the web has been

attached. One of its legs touches the line to alert the spider when prey is caught in the web.

Identification is relatively simple because of the characteristic star-shape of the abdomen formed by a series of cone-like bumps (protuberances). The spider is brown with a white spot on the anterior portion of the abdomen. Adults reach a length of about 3/8 inch. Adults and immatures differ only in size.

Numbers generally increase as the season progresses, reaching a peak in August and September when large numbers of immatures cover the countryside. Densities in cotton fields average about one per 10 meters of row but peak at one per 2 meters.

The star-bellied orb weaver does not hunt its prey but waits for prey to get caught in its web. Thus, it is likely that most of its prey fly or jump into the web. Adult fleahoppers, bollworm-budworm moths, bigeyed bugs, pirate bugs, damsel bugs and honeybees are frequent prey of this spider. There is no evidence that this spider feeds on bollworm or budworm eggs under field conditions, but it may consume one small larva every 2 days.

Grey dotted spider (Aysha gracilis [Hentz])

Grey dotted spider This spider is very similar in behavior and appearance to the winter spider. It is a night hunter and spends the day in a silken nest under leaves or bracts of squares. The adult is about 1/4 inch long and yellow with a darker anterior end and brown jaws (chelicerae). A pair of longitudinal grey bands is found on the back (carapace) between the eyes and the abdomen, and reddish-brown to black spots form two indistinct longitudinal bands on the abdomen. The legs are covered with spines; this helps distinguish it from the winter spider which has smaller and less distinct spines on the legs. Immatures resemble adults but markings are paler.

Peak numbers occur during August or September when one per 2 meters of row may be present. Usually fewer than one per 10 meters are found.

Little is known of its feeding habits in cotton, but it preys on about one bollworm-budworm egg every 10 days and one small worm every 2 days. Otherwise its prey is similar to that of the winter spider.

Black and white jumping spider (Phidippus audax [Hentz])

Black and white jumping spider feeding Common around homes and gardens, this spider hunts in the daytime and often is seen on window screens. It is common in cotton. Its black color is contrasted with three white spots on the abdomen of adults. These spots are reddish-orange on the immatures which also have reddish legs. Adults may reach inch in length and have large eyes on the front of the head. When attacking, they crawl to within striking distance and jump on their prey.

This spider generally increases its numbers throughout the season reaching a peak of about one per meter of row in August. Average density is about one per 10 meters of row.

Immature spiders feed on bollworm-budworm eggs and may eat five per day. This spider can capture and eat all larval stages of the bollworm-budworm; larger larvae are taken by the larger spiders. Under field conditions they may each eat about one worm every 2 days. Even boll weevil adults and bollworm-budworm moths are attacked. Immature spiders capture and consume fleahoppers, Lygus bugs and pink bollworm adults.

Long jawed orb weaver (Tetragnatha laboriosa [Hentz])

Long jawed orb weaver This elongated spider, less than 1/4 inch long, uses a web placed between branches of the cotton plant or between rows to catch its prey. Males have long jaws (chelicerae) from which this species gets its name. They are light yellow with a silvery abdomen. This spider often is found in the center of its web, which has an open hub.

A peak of about one per meter of row occurs in August with an average density of about one per 5 meters of row.

Feeding habits of this spider are not fully known, although they feed mostly on flying insects caught in their webs such as fleahoppers, leafhoppers and small moths.

Ridgefaced crab spider (Misumenoides formosipes [Walckenaer])

Ridgefaced crab spider feeding This crab spider is a hunter that usually waits in ambush for its prey in the terminal of the cotton plant. It can change color to match its background but is generally creamy-white to yellow or yellowish-brown with slightly darker sides. The abdomen may be unmarked or it may have red or brown markings that form a "V" pointing to the head. A white ridge crosses the face under the eyes.

An average density of only about one per 100 meters has been observed in May, although peaks of up to one per 10 meters have been observed. This spider feeds on fleahoppers and bollworm-budworm larvae and perhaps other insects.

Use of Predators

Current research in East Texas indicates that if any combination of the 16 predators discussed in this publication is found in the cotton field in numbers qual to or greater than bollworm-tobacco budworm eggs, insecticides usually are not needed. For example, if an average of 10 eggs and 10 predators are counted per meter of row, no insecticide is needed. Use caution during rainy weather when the predation level may decrease. However, if the rains do not continue more than I or 2 days, the predators may recover and prevent unacceptable losses.

Beat-bucket sampler Careful sampling of these predators is as important as sampling pests. Thus, securing the services of a well-trained field scout or consultant is a good investment. Farmers can also easily learn to do this themselves. A "beat-bucket" sampler is recommended as a simple and efficient tool for sampling predators and some pests. To make one, cut the bottom 10 inches from a white or light-colored S-gallon plastic bucket. To use the sampler, place the top 10 inches of the cotton plant inside the bucket and give five separate, rapid shakes from side to side. Then even the smallest predators can be counted in the bottom of the bucket.


INSECT PARASITISM OF COTTON PESTS

Allen Knutson and G.T. Bohmfalk

All animals and plants, including insects, have natural enemies that attack their various life stages. These natural enemies are what help keep explosive pest outbreaks from occurring. Important natural enemies of cotton pests include insect parasites.

A parasite is an organism that lives in or on another usually larger organism. Parasites of insects, termed parasitoids, are a special group of parasites since they kill their host. An insect parasite requires only one host to develop to the adult stage, which is free living.

Insect parasites feed internally or externally on their hosts. An external larval parasite (Euplectrus hircinus [Say]) is seen parasitizing a bollworm larva. The host may become paralyzed before it dies from the parasite's feeding. Insect parasites may attack any life stage oftheir host, but most parasitize the egg or larval stage. Egg and larval parasites lay their egg in a host egg or larva. The parasite egg hatches into a larva that kills the host egg or larva. Some insect parasites lay an egg in the host egg, larval or pupal stage, and the parasite finally kills a later stage (larva, pupa or adult).
External larva parasite Trichogramma parasitizing bollworm egg

Tiny wasps called Trichogramma are typical insect parasites. This wasp parasitizes bollworm and budworm eggs. The adult female wasp deposits her egg inside the bollworm egg. The wasp's egg hatches into a larva which feeds in the bollworm's egg. The full grown Trichogramma larva transforms into the adult wasp which escapes from the dead bollworm egg. The female wasp mates and flies in search of other bollworm eggs to parasitize, thus repeating the life cycle. Trichogramma also parasitizes other moth eggs. Figure 2. Trichogramma parasite life cycle on bollworm egg

In addition to Trichogramma wasps, bollworms and tobacco budworm larvae often areparasitized by other fly and wasp species. Many insecticides applied to cotton destroy insect parasites, which may result in economic infestations of bollworms, budworms or other cotton pests. The boll weevil, in contrast, has relatively few effective natural enemies, which explains in part why it is such a devastating pest.

Most parasites are so small and secretive they are seldom seen and their benefit is not always evident. Other parasites, including tachinid flies, braconid wasps and ichneumonid wasps, are larger and more often seen. Parasitic insects are valuable allies in keeping cotton pest populations below damaging levels.

Recognizing the value of parasitic insects and preserving natural enemies whenever possible is an important component of cotton integrated pest management.





THE COTTON PLANT

R.B. Metzer

The cotton plant usually is considered an annual, although it is a perennial in some parts of the world where it is grown commercially. The woody, herbaceous plant has a long tap root and attains a height of 2 to 5 feet or taller under favorable conditions. Cotton grows best with high temperatures and adequate soil moisture and fertility. Air temperatures in the 90 to 95 F. range are considered optimum for growth. Little or no growth can be expected at 60 F. or below. Temperatures in excess of 100 F. for several days can be unfavorable, especially if soil moisture becomes deficient. The tap root grows downward into moist soil at a rate of about 1 inch per day for 5 weeks or longer. During the growing season the daily growth rate of roots may average inch.

When cotton emerges, the first leaf structures are called cotyledonary or seed leaves. They appear on the lowest node and are borne on opposite sides of the main stem. The nodes above the seed leaves bear a single true leaf. These leaves have a spiral arrangement around the stem. The true leaves have five or more clearly defined lobes. At the base of each main stem leaf, in the angle between the leaf and the stem, there are two and sometimes three buds. They are called axillary buds and give rise to the vegetative and fruiting branches. The vegetative branches normally are restricted to the lower nodes on the stem. In most American upland cottons the first fruiting branch begins developing at the fifth or sixth node above the seedling leaves. The fruiting branches produce floral buds, called cotton squares that develop into bolls. Flowers (blooms) are creamy white when first open. Fertilization occurs on day that flowers open; it turns pink the day after anthesis. Then boll development begins. The interval between corresponding nodes on successive fruiting branches (vertical flowering interval) is 2 to 3 days, and the interval between successive flowers on the same fruiting branch (horizontal fruiting interval) is 5 to 6 days.

Flowering usually begins about 7 to 11 weeks after planting. Determinate varieties stop growing after boll development. In contrast, indeterminate varieties usually are late-maturing and continue flowering until stopped by frost, drought, insect attack or some other cause. The flower bud or square usually is discernible 3 to 4 weeks before the flower opens. Many of the buds, squares, flowers or young bolls drop off naturally. This is called shedding. As a result, it is estimated that only 35 to 40 percent of the squares produce mature bolls under normal conditions. The most critical time for developing fruit is 3 to 10 days after pollination. The period between flowering and opening of mature bolls is 6 to 8 weeks, depending on growing conditions. Cloudy conditions and below normal temperatures during this period can increase the boll maturation period.

Fruit of the cotton plant is the enlarged 3- to 5-loculed ovary commonly referred to as a cotton boll. Mature bolls vary in size and shape depending on the variety and environmental conditions but usually are 1 1/2 to 2 inches in diameter. Bolls set during the first 3 weeks of fruiting usually are the largest and contain the highest quality fiber. Normally, late set bolls are smaller and may contain finer and less mature fiber, depending on temperature and moisture levels during the boll maturation period. Normally, 65 to 90 bolls are required to produce a pound of seed cotton. However, some varieties produce relatively small bolls that may require 100 bolls or more to produce a pound of seed cotton.

Fiber length development is determined the first 3 weeks after flowering. Increase in micronaire value as well as fiber strength occurs during the next 3- to 4-week period after length is established. Moisture stress during the first 3 weeks after flowering can restrict fiber length. Adequate temperature is a critical factor in determining the strength and maturity of lint.

The cotton plant can adapt to different environmental stresses. In a severe drought, the plant may be only 6 inches high but still capable of producing several bolls. A plant of the same variety grown under adequate moisture or irrigation may be 5 feet in height and produce 40 to 50 bolls. Depending on other stresses, the number of bolls that develop is kept in balance with the vegetative growth of the plant. The fruiting-vegetative balance is affected by several factors. A shift to vegetative growth is associated with excessive nitrogen and soil moisture, coupled with cool, cloudy conditions. This shift is intensified even further if initial fruit set is poor or if excessive shedding has taken place. Warm, sunny weather and adequate but not excessive moisture and nitrogen and little insect stress encourage fruiting.

A population of 30,000 to 65,000 plants per acre is the optimum range for maximum yields. Although the cotton plant can adjust to variable spacing, uniform distribution of plants in the row produces the highest yields. A uniform plant spacing produces the highest yields. Under dryland conditions a plant population in the lower range is desirable, especially in low rainfall areas.

Cottonseed are frequently planted at rates higher than necessary to achieve adequate stands. A dense stand results in crowding in the drill-row. High plant population encourages fruit set at a higher position on the plant, which contributes to delayed maturity. Severe crowding can result in barren plants that function as weeds because they compete for moisture and nutrients. Barren plants usually are taller and are therefore more susceptible to lodging.

The time required for specific growth and development stages in the cotton plant is influenced primarily by planting date, variety, available moisture and temperature during the fruiting period. Other factors such as soil type and the level of insect, weed and disease pressure also can alter the time required to reach various growth and fruiting stages. Some important growth and fruiting variables of the cotton plant are presented below:

Average Growth and Fruiting of the Cotton Plant
Planting to emergence 4 to 10 days
Emergence to first true leaf 8 days
Emergence to second true leaf 9 days
Second true leaf to pinhead square (seventh node) 18 to 21 days
Pinhead square to matchhead square 9 to 10 days
Matchhead square to first one-third grown square 3 to 6 days
First one-third grown square to first white bloom 12 to 16 days
First white bloom to first open bolls 40 to 60 days
Harvest bolls set first 4 weeks of blooming 96%
Percent blooms that make bolls 35 to 40 %

Most fruit is set in the first 3 to 4 weeks of blooming. Squares are more easily shed than bolls. Once bolls are 12 days old or older, they usually will not shed unless the plant suffers severe stress (temperature, moisture, insects or disease).


CROP MONITORING (SCOUTING)

G.T. Bohmfalk

Integrated pest management evolved as several control techniques in harmony to keep pests below damaging levels. Experience shows that it is better to manage pests by using multiple suppression tactics rather than a single one. This includes using natural controls such as predators, parasites and pathogens and cultural strategies in combination with well timed insecticide applications in an integrated approach. Along with the development of this multitactic management system is an increased awareness of "in-field" insect and plant dynamics. This awareness is a result of constant crop monitoring of pests and beneficial insects and their effects on the cotton plant. This is the basis of cotton scouting.

Cotton scouting, or crop monitoring, is not a suppression tool itself but rather a means of gathering information on pests which will aid in management decisions. There is more to cotton monitoring than just checking for insects. It involves proper identification, a determination of pest and beneficial insect densities and their effects on the cotton crop as a whole. Insect numbers fluctuate a great deal. In cotton fields pests can increase to a point where, if not suppressed, they will cause economic damage to the crop. This pest density is called an economic threshold and is illustrated in figure 3.

Figure 3 . Economic threshold

The economic threshold is determined by research and practical experience. It has been approximated for most cotton pests but may vary with the area in which the crop is grown. For current information on the economic thresholds of cotton pests in your area, contact an Extension entomologist or your county Extension agent or refer to the Management of Cotton Insects series appropriate for your region.

Since evaluating the economic threshold involves observing a pest population that is truly dynamic and rises and falls periodically, there must be some method of systematic sampling on a regular basis. Sampling in cotton usually is done once or twice a week. Sampling results should be recorded in an easy-to-understand method (figure 4). Frequently, during peak insect activity, fields must be scouted or monitored more than twice a week. It is also critical to monitor the effects of other factors such as weather, disease, herbicidal injury, etc.

Figure 4. Producer's cotton insect report

Insect populations often are concentrated in certain areas of a field. Insects are not distributed uniformly in the field and do not infest all fields in an area. Large areas of the field must be covered each time. Scouting aids in determining the kinds of insects present, their location, relative abundance and distribution in the field and numbers of insects or amount of insect damage to the plants. Scouting only near turn rows and field margins is inadequate for determining insect infestation. To cover the field completely, walk a field in a "zigzag" pattern crossing it diagonally from one corner to another or walk it in-a wide arc taking samples from several plants (figure 5). The pattern followed should allow adequate sampling throughout the field, including the center, the sides and corners. Sampling pattern should be determined by the shape and size of the field. Avoid sampling in the same area of the field on successive sampling days.

Figure 5. Patterns used in scouting fields

The numbers and kinds of insects in a field usually are determined with reasonable reliability by examining squares and leaves from the terminal or entire plant or by sweeping the top part of a plant. Samples also may include any insects in the blooms, the rate at which squares are being set. the blooming rate. observable damage to bolls and the growth rate of plants. Determine any "natural" excessive square or boll shed when making an evaluation. Remember to consider the effect the weather has on the crop when evaluating fruit loss.

The part of the plant examined in a sample varies with the insect pest being sampled. Many insect infestations are assessed by taking "square" samples and determining the percent damaged by the particular insect. Other insects may be found primarily on terminal buds, so the terminal may be the best sampling unit. Taking leaf samples and counting the number of insects present or the amount of leaf damage provide infestation information for many leaf-feeding species. Sample plant bugs and other insects by using an insect sweep net. Black light traps and pheromone traps are survey tools useful for estimating the relative density of some insects in the area.

Take samples or count samples from the bottom, middle and top portions of the plants. Taking all the samples from the top can give an inaccurate count and let insect infestations concentrated on the lower parts of the plants go undetected. This is especially true for bollworms and tobacco budworms and their eggs, which are sometimes laid lower on plants in the hotter part of the season.

The number of samples taken when scouting a field usually is dictated by field size and field variability. In fields of 40 acres or less, usually only two samples are made. A single sample should consist of examining at least 25 individual plants at random or all plants in a predetermined length of row (6.5 feet or 13 feet) at each site. Make a record of pests, beneficials and plant damage. The data from all samples are totaled or averaged for the field. The number of samples should increase as the field size increases. Fields between 40 and 100 acres usually have four samples taken. In fields exceeding 100 acres, a sample is added for every additional 50 acres. For specific sampling instructions refer to the Management of Cotton Insect series for your region.


MONITORING COTTON FRUITING RATE

Monitoring the cotton fruiting rate is an excellent indicator of the growth and maturity of the cotton plant. Usually problem fields are detected promptly if fruiting rates are monitored accurately. Early fruiting is a desirable quality and frequent monitoring gives a good indication of crop set. To monitor fruiting rates, mark a point on a row and count 100 consecutive one-third grown (1/4 inch in diameter) or larger green squares. Record the number of row feet required to gain that count. One-third grown squares are preferred feeding- and egg-laying sites for boll weevils. This general square size also is preferred by bollworms/tobacco budworms; thus, it is a key indicator of potential damage. Also record the number of bolls observed in this distance. Later in the season, when squares are few, count 100 bolls, both green and open, and record the number of row feet required to make the count. To estimate the number of squares or bolls present per acre, divide the number of row feet required to gain a count of 100 squares or bolls into the number of row feet per acre (13,068 running row feet for 40-inch rows and 13,756 running row feet for 38-inch rows) and multiply by 100.

Bolls or squares per acre =  13,068 (or 13,756)     X 100
			   Number row feet recorded
			  for 100 consecutive bolls
				 or squares 

MANAGEMENT DECISIONS

R.E. Frisbie and G.T. Bohmfalk

The decision to control cotton insects and mites with insecticides should be made with care. Use insecticides only if the economic threshold has been reached, based on insect scouting results, the stage of plant growth and rate of fruit production. With the exception of a few microbial insecticides, insecticide applications typically depress beneficial (predator and parasite) populations that are important natural control agents. Low rates of certain insecticides such as ovicides have been less damaging to beneficial populations. Insecticidal control of one pest often affects the beneficial population suppressing another pest. The most frequent example is an insecticide applied near or at the bloom stage for boll weevil, which destroys beneficial insects that help keep the bollworm-tobacco budworm in check.

The growth stage of the cotton plant, in relation to its vulnerability to insect attack, is important to consider. One may view these susceptibility periods as "windows" in crop growth. Figure 6 illustrates these windows and their relationship, in time, with the plants growth stages. For example, the window for the cotton fleahopper is from pinhead size square through one-third grown square. After this period the cotton fleahopper usually does not have the potential to inflict damage. Windows of key pests may overlap and make decisions more difficult and risky. The best example of this is, again, with the boll weevil and the bollworm-tobacco budworm complex. The window for the boll weevil begins at one-third grown square and generally ends when a boll reaches 10 to 12 days of age. The window for the bollworm-tobacco budworm begins around the one-third grown square stage and extends past and overlaps with the boll weevil window.

Figure 6. Season chart of cotton and main cotton pests

Research shows that the most critical period of fruit formation is in the first 30 to 40 days of blooming. The highest quality and quantity of lint is produced at this time. Thus, damage inflicted in this window can be most costly. Strategies in cotton insect management show that the boll weevil can be managed effectively in various parts of the state by altering the planting date, if practiced uniformly, or by selected insecticide applications early in the boll weevil window (first one-third grown square stage), based on field scouting information. Either of these strategies, if properly practiced in most years, neutralizes the boll weevil as a pest, allows theplant to set and hold early fruit and delays boll weevil build-up until the critical 30 to 40 days of blooming can take place. Of equal importance, this strategy has little effect on beneficials that naturally control bollworm-tobacco budworm populations.

By viewing growth of the cotton plant as a series of susceptibility windows, management decisions and scouting information can be targeted to deal with the specific major pests attacking cotton. By considering the pest within a certain window (time-frame), its damage can be assessed relative to the growth stage and its potential to destroy harvestable fruit.


OTHER INSECT PEST MANAGEMENT PRACTICES

A field sterile of all pest insects is neither necessary nor desirable. However, do not allow harmful insects to reach numbers that will cause unacceptable losses. Keep them below the economic threshold. Excessive use of nitrogen fertilizer causes cotton plants to stay green and stimulates rank growth. The excessive, rank growth can reduce cotton yield and increase damage from the bollworm-tobacco budworm. Rank growth also makes it difficult to achieve thorough plant coverage with insecticides.

Cotton planted too thick becomes tall and "leggy" before it sets squares. This condition is often wrongly blamed on cotton fleahoppers. Maximum yields are produced when cotton is planted at a rate of two to four plants per foot of row on 40-inch rows. Current research in this area on narrow row spacings is being evaluated for use by cotton producers in various production areas.

Foliage and fruit on cotton stalks remaining in a field after harvest can supply a food source for boll weevils, bollworms, tobacco budworms and pink bollworms that allows these pests to continue growing and reproducing. This increases the number of overwintering pests. Cut stalks and plow fields immediately after the cotton is picked or stripped.

By planting cotton at a uniform time throughout an area, many problems with boll weevils, bollworms and tobacco budworms and pink bollworms can be reduced greatly. These insect pests are attracted to the older cotton plants of early planted cotton. Late season damage by bollworm-tobacco budworm often is greater on later planted cotton which remains green and lush longer than earlier planted cotton. Later planted cotton also may have more squares which aid in the development of high numbers of boll weevils.


INSECT IDENTIFICATION AND DAMAGE-DIAGNOSTIC KEY

G.T. Bohmfalk

This simple key is designed to help the producer diagnose damage caused by insects and spider mites. Although it is pest-oriented, cues are provided to aid in separating pest identification from beneficial identification. Extension entomologists can assist with identifications .

Symptom Suspected insect
Seeds
Seeds eaten, resulting in poor stand Fire ant or seed-gathering ant (not common)
Seeds hollowed out Wireworms (not common)
Seedling
Stems cut off evenly at or near ground level; chewed at base Cutworms Grasshoppers
Cotyledons and first rue leaves deformed or "cupped downward" with honeydew present Aphids or whiteflies (Whiteflies may not deform leaves but honeydew is present.)
Cotyledons and first true leaves deformed, "cupped upward" with no honey dew but with a silvered appearance Thrips
Ragged holes eaten in leaves Armyworms
Cabbage looper
(grasshoppers)


Established Stand Through Squaring
Symptom Suspected Insect
Leaves
Discolored, reddened or "mottled"
some slight webbing obvious on
underside
Spider mite
With "shot-hole" appearance; mining
and horseshoe-shaped larvae present
Cotton leaf perforator
Skeletonized with numerous small larvae present Armyworms
Numerous large holes and feeding on margin Cabbage looper or grasshoper
Ragged and completely eaten with
"woolybear" caterpillars present
Saltmarsh caterpillar
Rolled with webbing present Omnivorous leaf roller
Squares
Blackened or "blasted"
Lygus bugs
Cotton fleahopper
Eaten into with frass present, hole
circular and square may be hollowed out
Bollworm and/or tobacco budworm
Eaten into with clean feeding site hole
slightly flattened and square not
completely hollowed out
Cotton square borer
Bracts primarily fed on Beet armyworm
Tiny feeding sites with bright orange to
yellow excrement present; small wart-like,
egg-laying sites
Boll weevil
Blooms
Holes in base Armyworms
Bollworm and/or
tobacco budworm
Rosetted petals Pink bollworm
Disfigured, twisted and coarse Lygus (plant) bug,
cotton fleahopper
or stink bug
Terminal
Tunneling in terminal
Bollworm-budworm,
fall armyworm or
omnivorous leaf roller


Boll Set and Maturity
Symptom Suspected Insect
Bolls
Holes with frass present; hole circular Bollworm and/or
tobacco budworm
Beet armyworm
Fall armyworm
Tiny holes with some yellow to bright
orange frass and wart-like, egg laying sites
Boll weevil
Small depressions and "cat-facing" Lygus bug
Stink bug
Holes through boll, carpel walls and seeds Pink bollworm
Soft, dark area with cream colored grub
inside boll
Boll weevil


Insect Egg Diagnosis
Symptom Suspect Insect
Occurring singly
White to tan, eventually turning brown,
spherical with lines from base to tip,
usually in terminal areas or underside of
tender young leaves and on stems
Bollworm and/or
tobacco budworm
Slightly flat, greenish-white, laid on leaf
surface
Blue-green, flat and laid singly over
leaves
Cabbage looper
White or green supported by a silken
stalk
Lacewing
White, oblong, lays on side on leaves
and stems
Bigeyed bugs
Silken bag attached to plant Spiders
White, oval, flattened, somewhat donut-
shaped, surface covered with net-like lines
Cotton square borer
Occurring in groups
Pale green covered with scales and usually
deposited on underside of leaves
Armyworms
Blue-green, flat and overlapping like
shingles usually on upperside of leaves
Omnivorous leaf
roller
Brownish, "barrel-shaped," tightly
packed
Stink bugs
Orange, shiny and cigar-shaped with few
in cluster
Lady beetle


Insect Larval Diagnosis
Symptom Suspect Insect
Found outside of bolls or squares
Large, covered with dense yellow to
brown hair
Saltmarsh
caterpillar
Body with no hair, head capsule smaller
than distal end, pale green, moves with looping
action
Cabbage looper
Body having sparse hairs or spines; may be
striped with mottled head capsule
Bollworm and/or
tobacco budworm
Green with a tiny black spot above second
true leg; without even small hairs
Beet armyworm
Black to dark green with yellow and
brown stripes
Yellowstriped
armyworm
Brown with dark patches on the sides; plae
to white inverted "Y" on face of head
capsule; body sparsely covered with short,
dark hairs
Fall armyworm
"Football-shaped" with dense, velvet hair
covering, bright green to yellow
Cotton square
borer
Smooth, olive green with white spots on each
segment; darkened head; slender worm
often found rolled in cotton leaves
Omnivorous leaf
roller
Tiny, white to dark green, marked with
darkened areas, foundwithin the leaf
itself or on the surface
Cotton leaf-
perforator
"C"-shaped, variable in color, in or on the
soil surface; "C"-shaped when disturbed
Cutworms
Found only inside bolls or squares
Small whitish or pink larva inside
maturing boll
Pink bollworm
Small, grub-like larvar found in squares
or developing bolls
Boll weevil


ADDITIONAL BENEFICIAL INSECTS


Additional beneficial insects
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no dicrimination is intended and no endorsement by the Cooperative Extension Service is implied.

Educational programs conducted by the Texas AgriLife Extension Service serve people of all ages regardless of socioeconomic level, race, color, sex, religion, handicap or national origin.

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Ed Smith, Director, Texas AgriLife Extension Service.

Electronic Revision, 2011

ENT



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Last modified: January 12, 2011 by Billy E. Warrick