For recommended insecticides refer to E-5A, "Suggested Insecticides for Managing Cotton Insects in the Southern, Eastern and Blackland Areas of Texas-2003" at the following web sites:

http://insects.tamu.edu/extension/bulletins/e-5a.html or http://tcebookstore.org

A committee of state and federal research personnel and Extension specialists meets annually to review cotton pest management research and management guidelines. These guidelines are directed toward maximizing profits for the Texas cotton producer by minimizing inputs and optimizing production output.

The term "pest management" applies to a philosophy used in the design of insect, mite, disease and weed pest control programs. It encourages the use of the most compatible and ecologically sound combination of available pest suppression techniques. These management techniques include: cultural control, such as manipulation of plating dates and stalk destruction; crop management practices, such as variety selection and timing of irrigation; biological control, involving conservation of existing natural enemies; host plant resistance; and the wise use of selective insecticides and rates to keep pest populations below economically damaging levels.

Major factors to be considered when using insecticides include protecting natural enemies of cotton pests, possible resurgence of primary pests, increased numbers of secondary pests following applications and pest resistance to insecticides. Therefore, insecticides should be applied at the proper rates and used only when necessary, as determined by frequent field inspections, to prevent economic losses from pests.

The pest management concept rests on the assumption that pests will be present to some degree in a production system, and that at some levels they may not cause significant losses in production. The first line of defense against pests is prevention through the use of good agronomic practices or cultural methods which are unfavorable for the development of pest problems (discussed below). Properly selected control measures should be taken only when pest populations reach levels at which crop damage suffered could result in losses greater than the cost of the treatment. This potentially injurious pest population or plant damage level, determined through regular field scouting activities, is called an economic threshold or action level. Precise timing and execution of each production operation are essential. In short, pest management strives to optimize rather than maximize pest control efforts.

Experience has shown that reliance on a single class of insecticides that act in the same way may cause pests to develop resistance to the entire group of insecticides. A good strategy to help avoid pest resistance is to rotate the use of insecticide groups, in order to take advantage of different modes of action. Such insecticide management should delay the development of resistance and also provide better overall insect control.

Insecticides with similar chemical structures act on insects in similar ways. For example, pyrethroids (including esfenvalerate, bifenthrin, cyfluthrin, cyhalothrin and tralomethrin) all act on an insect’s nervous system in the same way. Other types of insecticides such as organophosphates (methyl parathion, dicrotophos) or carbamates (thiodicarb) also affect the insect’s nervous system but in a different way than do the pyrethroids.

Insect and mite infestations are often held below damaging levels by weather, inadequate food sources and natural enemies such as disease, predators and parasites. It is important to recognize the impact of these natural control factors and, where possible, encourage their action. (See B-6046, "Guide to the Predators, Parasites and Pathogens Attacking Insect and Mite Pests of Cotton" Texas Cooperative Extension.)

Biological control is the use of predators, parasites and disease causing organisms to control pests. Important natural enemies in cotton include minute pirate bugs, damsel bugs, big-eyed bugs, assassin bugs, lady beetles, lacewing larvae, syrphid fly larvae, spiders, ground beetles and a variety of tiny wasps that parasitize the eggs, larvae and pupae of many cotton pests.

Biological control includes the conservation, importation and augmentation of natural enemies. It is an environmentally safe method of pest control and is a component of integrated pest management programs in cotton. The Texas A&M University System is fully committed to the development of pest management tactics which use biological control.

Existing populations of natural enemies are conserved by avoiding the use of insecticides until they are needed to prevent the development of economically damaging pest infestations. Insecticide impact can also be minimized by using insecticides that are more toxic to the target pest than to the natural enemy. Classical biological control is the importation of natural enemies from other countries. This method has been effective where an exotic pest has entered Texas without its incumbent natural enemies, or to augment natural enemies of native pests.

Augmentation involves the purchase and release of natural enemies on a periodic basis. The most notable commercially available natural enemies include the egg parasite Trichogramma, and the predators, lady beetles and lacewings. Although the control of both bollworms and tobacco budworms by the release of commercially reared Trichogramma wasps is theoretically possible, researchers have not been able to consistently achieve the level of parasitism necessary to reduce infestations below economically damaging levels. Multiple Trichogramma releases at high rates ranging from 50,000 to 150,000 parasitized eggs per acre were utilized in these studies. There are currently no economic thresholds established for augmentative releases of Trichogramma for bollworm/budworm control in cotton. Furthermore, parasite mortality from insecticides used to control other pests in or around parasite release areas would limit the effectiveness of augmentative releases.

Research has shown that releasing large numbers of lacewing larvae (30,000 or more per acre) can reduce bollworm infestations below damaging levels. However, these release rates are currently cost prohibitively because of high lacewing rearing costs. The release of lacewing eggs has been less successful and there is little information on the efficacy of releasing adult lacewings in cotton. There is even less information relative to releasing either lady beetles or lacewings for the control of aphids.

Because there is too little information about augmentation (when to apply, what density should be applied, etc.), entomologists with Texas Cooperative Extension cannot provide guidelines for augmentation as a management tool in cotton.

Bt cottons are insect-resistant cultivars and one of the first such agricultural biotechnology products to be released for commercial production. Insect resistance in the Bt cottons was engineered by the introduction of a bacterial gene that produces a crystalline toxin, which, in turn, kills feeding larvae of several cotton pests. The toxin in Bollgard™ cottons has excellent activity against tobacco budworm, pink bollworm, cotton leaf perforator and European corn borer, and good activity against cotton bollworm, saltmarsh caterpillar and cabbage loopers. When the infestation is heavy, supplemental insecticide treatment may be necessary for bollworm. Bt cottons provide some suppression of beet armyworm and soybean looper, and little or no control of fall armyworm or cutworm. In all cases, economic thresholds used for Bt cottons should be the same as those used for non-Bt cottons, but should be based on larvae larger than 1/4 inch and damage, not on eggs or early instar larvae. For additional information on Bt cotton refer to L-5169, "Bt Cotton Technology in Texas" available from your county Extension office.

The short-season cotton production system is crucial in reducing insect damage. This system includes cultural practices such as: 1) early, uniform planting of cotton varieties which bloom and set bolls early, mature rapidly and are ready to harvest 130 to 150 days from planting (refer to county cotton demonstrations for varieties that have performed well in your area); 2) optimum use of fertilizer and minimum irrigation; and 3) early, complete stalk destruction. These practices shorten the time that cotton is vulnerable to insect attack, minimize potential damage from adverse weather, and allow more time to prepare land for the next crop. Failure to implement these cultural practices will increase the probability of late-season boll weevil and bollworm outbreaks, increase the need for insecticides and cause larger populations of overwintering pests to develop. (See Early Stalk Destruction and Field Cleanup p.6).

The first 30 days of blooming are critical for early boll set. The earliness factor in short-season production can be lost when damaging populations of insects occur as the first squares are formed. Loss of first squares to overwintered boll weevils also will detract from short-season production. To ensure early fruit set, scout fields to determine pest population levels and plant damage, as well as beneficial insect numbers and cotton fruiting rate. Use chemical insecticide only when justified. Insecticides may destroy natural enemies of cotton insect pests, causing increased numbers of bollworms, tobacco budworms, spider mites and cotton aphid.

To monitor fruiting rates, fields should be examined weekly or biweekly. During each visit, mark a point on a row and count 100 consecutive 1/3-grown or larger green squares; record the number of row feet required to gain that count. Later in the season when there are fewer squares, count 100 consecutive bolls, both green and open. Record the number of row feet required to make this count. To estimate the number of squares and/or bolls present per acre, divide the number of row feet counted into the number of row feet per acre (13,068 on 40-inch rows, 13,756 on 38-inch rows, 14,520 on 36-inch rows and 17,424 on 30-inch rows) and multiply by 100. Row feet per acre also can be obtained by dividing 522,720 by the row spacing in inches.

After moisture, the most important factor in development of squares and bolls is temperature. Researchers have devised a way to describe and measure the relationship between cotton development and temperature-the heat unit concept or DD60 (degree days using 60 degrees F). Heat units measure the amount of useful heat energy a cotton plant accumulates each day, each month and for the season. The plant must accumulate a specified level of heat units for it to reach each development stage and to achieve complete physiological maturity.

Several systems have been developed to calculate heat units, but the most universal approach is to use the formula ((Degrees F Maximum + Degrees F Minimum)/2) - 60.

Bolls and/or squares per acre = (13,068 or 13,756 or 14,520 or 17,424/No. row feet examined) x 100

Early harvest and stalk destruction are among the most effective cultural and mechanical practices for managing overwintering boll weevils if done on an area wide basis. These practices reduce habitat and food available to the boll weevil, pink bollworm, bollworm and tobacco budworm. Shred cotton at the earliest possible date and do not allow stubble regrowth or volunteer seedlings to remain within fields or surrounding field margins or drainage system banks. Particular attention should be given to the destruction of green or cracked bolls and other plant debris left at the ends of rows following stripper harvest. Cotton present during the fall and winter months is illegal in the Rio Grande Valley and most counties in the Lower Coastal Bend, South Texas and the Blacklands (refer to "Cotton Pest Regulations" available from the Texas Department of Agriculture). This cotton provides the boll weevil with a host plant on which reproduction occurs throughout the year. Weevil infestations that are allowed to develop during the winter may result in extremely high populations during the following season. If a thorough stalk destruction program is not carried out, the benefits of the pest management program will be reduced significantly.

The addition of 0.5 lb ai/ac methyl parathion or 0.25 lb ai/ac azinphosmethyl (Guthion^® ) to phosphate-type defoliants has proven effective in reducing potential overwintered boll weevils. Do not add methyl parathion or azinphosmethyl to chlorate-type defoliants because of the potential fire hazard. The use of insecticides at defoliation will be effective only if stalk destruction is promptly performed following harvest. The greatest impact from insecticides is realized when applied on an area wide basis. If 3 to 4 weeks elapse between defoliation and stalk plow-up, the money spent on insecticides at defoliation will provide less benefit in boll weevil management. Weevils will continue to emerge, feed, reproduce and move from cotton fields following harvest.

Upon request and petition of Texas Cotton Producers, the Texas Legislature passed the Cotton Pest Control Law in an effort to combat the boll weevil and pink bollworm. This law, which is enforced by the Texas Department of Agriculture, requires producers in a regulated county to culturally manage pest populations using habitat manipulation by planting and destroying cotton within an authorized time period. Appointed producers, who are members of local pest management zone committees, have established a series of cotton planting and stalk destruction deadlines for all producers in each regulated county. The battle against pink bollworms has been extremely successful. Because farmers have adhered to authorized planting and stalk destruction deadlines over the past years, pink bollworm populations in most of the state have been reduced to levels that do not cause major economic damage. Boll weevil population control through stalk destruction efforts has been significant but more growers need to be involved in the effort. Strict adherence to the established deadlines is critical to success of boll weevil management.

Control measures are needed when a pest population reaches a level at which further increases would result in excessive yield or quality losses. This level is known as the "economic threshold" or treatment level. The relationship between pest level, amount of damage and ability of the cotton plant to compensate for insect damage is greatly influenced by crop phenology and seasonal weather. The economic threshold is not constant but varies with factors such as the price of cotton, cost of control and stage of plant development.

When a cotton field is properly scouted, accurate and timely decisions can be made to optimize control efforts while minimizing risk. Fields should be inspected every 3 to 7 days using the scouting procedures described in this guide for the various pests.

Regular field scouting is a vital part of any pest management program because it is the only way reliable information can be obtained to determine if and when pest numbers reach the economic threshold. Scouting should involve more than just "checking bugs." Scouting determines the insect density and damage levels through the use of standardized, random repeatable sampling techniques. Scouting should also include monitoring plant growth, fruiting, weeds, diseases, beneficial insect activity, and the effects of implemented pest suppression practices.

Scouting for predators. Predatory insects and spiders can sometimes maintain densities of bollworm, aphids and other pests below economic levels. Knowing the densities of common predators can be important when deciding whether to apply an insecticide for these pests. Also, monitoring densities of predators can alert the producer to those fields that are at risk of pest outbreaks because of low predator densities. Sampling predators can also measure the impact of previous insecticide applications on predator numbers.

The number of predatory insects and spiders in cotton can be rapidly and accurately determined by the beat bucket method. This method is more reliable and faster than searching the plant for predators. The beat bucket method uses a common white, 5-gallon plastic bucket or pail about 14 inches deep and 10 inches in diameter. To use the beat bucket, carefully approach the sample plant and grasp the stem near the base of the plant. While holding the bucket at a 45- degree angle to the ground, quickly bend the plant into the bucket so that the terminal and as much of the plant as possible are inside the bucket. Still holding the stem near the base of the plant, rapidly beat the plant against the side of the bucket 12 to 15 times during a 3- to 4-second period. This dislodges predators from the plant so that they fall into the bottom of the bucket. Quickly take one step, sample a second plant and then another step and sample a third plant down the row. Banging the side of the bucket with the hand will knock down predators crawling up the side of the bucket while sampling. After the third plant is sampled, record the number of bollworm predators (pirate bugs, spiders, big-eyed bugs, lacewing larvae) and others of interest (lady beetles, etc.) captured in the bucket. Remove and examine any leaves and bolls that fall into the bucket to be sure all predators are visible for recording. Tapping the bottom of the bucket can sometimes encourage predators that are playing dead to begin moving and become apparent. The bucket must be kept clean so that the predators are easily seen.

The table below shows the number of samples, from actual field data, required to estimate predator densities with the same level of precision when sampling with the beat bucket (3 plants per bucket), a sweep net ( 5 sweeps per sample) or visually searching the plant. The beat bucket requires fewer samples for most common predators than the sweep net and far fewer samples for all predators when compared to visually searching the plant. The sample sizes in this example are calculated for predator densities averaging 0.5 per plant. More samples would be required when predator densities are lower and fewer samples are required when predator densities exceed 0.5 per plant.

Refer to B-6046, Guide to the Predators, Parasites and Pathogens Attacking Insect and Mite Pests of Cotton (See p. 16 to order) for information on identifying common predatory insects and spiders in cotton.

Scouting for pests. The following general discussion briefly reviews the insect pests of cotton (for more detail see B-933, "Identification, Biology and Sampling of Cotton Insects"). The insect pests are discussed as they normally would occur throughout the cotton production season.

Early-season is the time from plant emergence to first 1/4-inch diameter (1/3-grown) squares. Major early-season pests include thrips, aphids, fleahoppers and overwintered boll weevils.

Scouting and management of early-season insect pests are extremely important, particularly in a short-season production scheme. Loss of early squares may prolong the length of the growing season required to obtain adequate fruit set.

Thrips are slender, straw-colored insects about 1/15 inch long, with piercing-sucking mouthparts. Adults are winged. Thrips attack leaves, leaf buds and very small squares, and may cause a silvering of the lower leaf surface, deformed or blackened leaves, terminal loss and square loss. Under cool, wet conditions heavy thrips infestations may reduce stands, delay fruiting and delay crop maturity.

Management and decision making. Early infestations often reduce yield more than later infestations. Thrips often infest the folded small leaves of the plant terminal and are difficult to count unless the terminal area is dissected. This is especially true during rainy, windy conditions. Inspect cotton from the cotyledon stage through the 6-true-leaf stage. The decision to apply insecticide should be based on the number of thrips present and the stage of plant development. The number of thrips per plant to use as a treatment level increases as plants add more leaves. Control may be justified when the average number of thrips counted per plant is equal to the number of true leaves present at the time of inspection. One thrips per plant should be used as the treatment level from plant emergence through the cotyledon stage to the first true leaf. Inspections should begin once cotton has reached approximately 50 percent stand emergence. Insecticidal control is rarely justified once plants reach the 5- to 7-true-leaf stage, or when plants begin to square.

Thrips can also be controlled by applying systemic insecticides as seed/planterbox treatments or as granules in the seed furrow (See Systemic Insecticides for Early-Season Pests, p. 13). Seed treatments can effectively control thrips for 1 to 4 weeks following plant emergence under good growing conditions. Granular materials (disulfoton, phorate and aldicarb) applied in the seed furrow will control thrips for 4 to 8 weeks following planting; however, use at the higher labeled rate sometimes reduces natural enemies, which can lead to secondary pest problems.

Three species of aphids, or plant lice, feed on cotton plants: the cotton aphid, the cowpea aphid and the green peach aphid. Cotton aphids range from light yellow to dark green to almost black. The immature or nymphal stage looks like the adult stage, only smaller. Most adults do not have wings. Cowpea aphids are shiny black with white patches on the legs and are common on seedling plants. Green peach aphids range from pale yellow to green. Winged migrant forms have a yellowish-green abdomen with a dark dorsal blotch. Aphid infestations can occur from plant emergence to open boll. Aphids usually are found on the undersides of leaves, on stems, in terminals and sometimes on fruit. Heavy and prolonged infestations can cause leaves to curl downward and older leaves to turn yellow and shed.

Natural control by unfavorable weather, predators, parasites and pathogens can be effective in holding populations below damaging levels. Sometimes aphid numbers increase to moderate or heavy levels and then decline for no apparent reason.

Management and decision making. Although high populations can develop prior to bloom, most economically damaging infestations develop later in the season during the blooming period. Fields should be scouted twice per week since rapid increases in aphid numbers can occur in a short time. A total of 60 leaves divided between the top, middle and lower portion of the plant should be sampled from plants across the field to determine infestation levels. Insecticidal control of cotton aphids should be delayed until infestations exceed 50 aphids per leaf. Refer to the latest Cotton Aphid Task Force Suggestions for further management information. These are available at the county Extension office.

Adult fleahoppers are about 1/8-inch long and pale green. Nymphs resemble adults but lack wings and are light green. They move very rapidly when disturbed. Adults move into cotton from host weeds when cotton begins to square. Both adults and nymphs suck sap from the tender portions of the plant, including small squares. Pinhead size and smaller squares are most susceptible to damage.

Management and decision making. The decision to apply insecticide should be based upon the number of fleahoppers present and percent square set. As the first small squares appear (approximately 4 to 6-leaf stage), examine the main stem terminal buds (about 3 to 4 inches of plant top) of 25 plants at each of at least four locations across the field. More sites should be sampled in fields larger than 80 acres. During the first 3 weeks of squaring, 10 to 15 fleahoppers per 100 terminals may cause economic damage in the Blackland area. In other areas, 15 to 25 fleahoppers per 100 terminals is considered economically damaging. As plants increase in size and fruit load, larger numbers of fleahoppers may be tolerated without yield reduction. When plants are blooming, fleahopper control is rarely justified. In addition, insecticides applied early in the blooming period may result in outbreaks of bollworms and tobacco budworms because of the destruction of predaceous insects and spiders. Use suggested higher application rates only when infestations are severe.

The tarnished plant bug is one of several Lygus species that feeds on cotton terminals, squares and small bolls. Adults are winged, vary in color from greenish to brown, and are 1/4 inch long. Immature tarnished plant bugs are called nymphs. They are light green and late instars have four conspicuous black spots on the thorax and one large black spot near the base of the abdomen. The nymph’s wings are not developed, but nymphs can move rapidly and are difficult to detect in cotton foliage. Small nymphs may be confused with aphids, cotton fleahoppers and leaf hopper nymphs. Plant bugs prefer legumes to cotton and usually are found in large numbers in areas of alfalfa production or areas providing wild hosts, such as clovers, vetches, mustard and dock. Lygus bugs are attracted to succulent growth; their feeding results in shedding of squares and small bolls, stunted growth and boll deformation. Damage to blooms appears as black anthers and puckered areas in petals.

Management and decision making. The need for lygus bug control is determined by their abundance in relation to the fruiting condition of the cotton plants. Inspect fields at 4 to 5-day intervals during the first 6 weeks of squaring. Take 50 sweeps at each of the four locations in the field by sweeping a 15- to 16-inch net across the top of one row only in such a way that the top 10 inches of the plants are struck. During the first 6 weeks of squaring, control measures should be considered when lygus bug numbers average 10 (count nymphs as two) per 50 sweeps on more than two successive sampling dates (spaced 5 days apart).

Overwintered boll weevils emerge from winter hibernation sites and enter cotton early in the season. They generally occur in very low numbers and females lay few eggs until first squares are about 1/4 inch in diameter (1/3-grown). Insecticides applied at this time (see control suggestions) will help suppress boll weevil population buildup until after peak bloom. In many years this allows the plant to set a large number of bolls early, while having little adverse effect on mid and late-season beneficial insects.

The need for insecticide applications to suppress overwintered, boll weevils can be determined by: 1) pheromone trap collections as discussed below; 2) field scouting results; or 3) the history of the field. In some regions insecticides are automatically applied, particularly in fields bordered by wooded or brushy areas which serve as overwintering habitats.

Six to eight pheromone traps are required for a field of 50 to 300 acres. Traps should be evenly spaced around the field margin. The treatment decision is based on the "Trap Index" (TI) and scouting information. The TI is calculated by averaging the number of weevils captured per trap each week, then adding these averages together for the 6 weeks prior to the first 1/3- grown square stage. The following TI’s were developed using the Hardee trap, and can be used for making treatment decisions.

Management and decision making. Control measures should be taken in fields where at least one weevil is found by the 1/3-grown-square stage, where pheromone trap results indicate the need for treatment, and/or where the field has a history of boll weevil infestations. These early applications should not be made in fields far from overwintering sites or where population buildup in past years has not occurred. As the plant develops and matchhead-sized (3/16-inch diameter) squares are present, the field should be scouted for the presence of adult boll weevils. Inspect at least 100 plants in the portion of the field where plants are largest and/or nearest to overwintering habitats. If a single boll weevil is found, the economic threshold level has been reached, and an insecticide should be applied to prevent egg laying. Where possible, band insecticides over the row. The second application should be made 4 to 5 days after the first. Do not make this application within 10 days of bloom to allow beneficial insect and spider populations time to reestablish in anticipation of bollworm infestations. There is always a risk of increased bollworm activity after these treatments.

Mid-season is the 6-week fruiting period following the appearance of the first 1/4-inch diameter (1/3- grown) squares. Proper crop management and frequent field inspection for pests and beneficials will eliminate unnecessary insecticide applications during this period. This procedure ensures adequate fruit set and preserves beneficial insects.

Late-season is the remainder of the production season when the major concern is boll protection. Heavy irrigation and high rates of fertilizer prolong cotton plant growth and increase the chance of late-season insect damage.

Bollworms, tobacco budworms and boll weevils are the principle insect pests in mid- and late-season. A major goal of a well-planned pest management program (although not always achieved) is to avoid having to treat for bollworms and tobacco budworms. Naturally occurring parasites and predators and certain weather conditions often suppress bollworm and budworm populations. For this reason, chemical control for the boll weevil at this time of year should be avoided if possible. If a satisfactory fruit set occurred during the first 30 days of blooming, higher numbers of weevil-damaged squares can be tolerated. However, if fruiting is delayed, additional insecticide applications may be necessary to protect smaller bolls that are expected to mature. Fewer boll weevil-damaged bolls can be tolerated if cotton is to be picked instead of stripped.

Adult weevils puncture squares or bolls both for feeding and egg laying. Egg laying punctures can be distinguished from feeding punctures by the presence of a wart-like plug which the female places over the feeding site after she has deposited an egg in the cavity. The female deposits an average of 100 eggs during her life span of about 30 days.

Eggs hatch into larvae (grubs) within 3 to 5 days under midsummer conditions. Grubs transform into pupae within the square or boll in approximately 7 to 11 days. Adults emerge 3 to 5 days later. Recently emerged adults feed on squares or bolls for 4 to 8 days before mating and laying eggs. The time required for development from egg to adult under summer field conditions averages 17 days, with a complete generation occurring in 21 to 25 days.

Punctured squares flare open and usually fall to the ground in about a week. Small bolls that are punctured may also fall to the ground, but larger bolls remain on the plant. When direct sunlight and hot, dry conditions cause fallen squares to dry out rapidly, large numbers of weevil larvae do not survive.

Boll weevil populations reach the highest level late in the growing season. As cotton plants mature and the number of squares is reduced, the percentage of boll weevil-damaged squares becomes an unrealistic indicator of damage because boll weevils are competing for squares. As square numbers decrease, boll weevils may cause more damage to small bolls.

Management and decision making. Refer to the overwintered boll weevil section above before the first 1/4- inch diameter (1/3-grown) squares are present in the field. Later in the season, at weekly intervals, inspect 100 squares that are at least 1/3-grown. Take squares from at least four representative locations in the field and from various portions of the plants. If 15 to 25 percent of the squares are weevil-damaged from the time of squaring to peak bloom, the economic threshold level has been reached and insecticide application is necessary. It may be necessary to repeat applications at 5-day intervals, or at 3-day intervals if weevil population buildup is extremely heavy.

After peak bloom, if 60 percent or more of the bolls are at least 30 mm (1 1/4 inch) in diameter, higher rates of damaged squares can be tolerated. However, additional applications may be necessary to protect smaller bolls if they are to be harvested. Where economic weevil infestations are encountered, protect bolls until the last bolls expected to be harvested are 12 to 15 days old.

Fire ants are effective predators of boll weevil larvae and pupae, although they will not prevent adults from migrating into the field and laying eggs. Fire ants can be sampled by the beat bucket method. Insecticides usually are not needed for boll weevil control when an average of four or more fire ants is collected per 10 terminal samples.

Bollworm and tobacco budworm larvae are similar in appearance and cause similar damage. Full-grown larvae are about 1 1/2 inches long and vary in color from pale green to pink or brownish to black, with longitudinal stripes along the back.

Tobacco budworm and bollworm moths are attracted to and lay eggs readily in cotton that is producing an abundance of new growth. Moths usually lay eggs singly on the tops of young, tender terminal leaves in the upper third of the plant. Eggs are pearly white to cream colored and about half the size of a pinhead. These should not be confused with looper eggs, which are flatter and usually laid singly on the undersides of leaves. Eggs hatch in 3 to 4 days, turning light brown before hatching. Young worms usually feed for a day or two on tender leaves, leaf buds and small squares in the plant terminal before moving down the plant to attack larger squares and bolls. When small worms are in the upper third of the plant, they are most vulnerable to control by insecticides and beneficial insects and spiders.

Budworms are generally more resistant to insecticides than bollworms. Budworms are less numerous than boll-worms early in the crop season and rarely reach high numbers until mid to late-season. Once certain kinds of conventional insecticides are used to control bollworm and budworms, the percentage of budworms in the infestation increases with each additional application because of selection pressure. Aphid and other secondary pest infestations may increase following bollworm/budworm sprays, especially when pyrethroids are used.

Management and decision making. Fields should be carefully scouted at least once a week and twice weekly during peak periods of egg deposition. Eggs and newly hatched worms are usually found in the plant terminals and indicate possible outbreaks. Natural mortality agents such as weather and predators frequently control these stages before any damage occurs. Once worms reach 1/2 inch long, natural control factors are much less effective.

Frequently, examination of the upper third (terminal) of the plant (leaves, stems, squares, blooms and bolls) for eggs and small larvae is all that is needed to make sound management decisions. However, moths sometimes deposit eggs on the fruit and stems lower on the plant. This may occur when cotton plants are stressed and making little new growth, or during periods of high temperatures and low humidity. Detection of eggs and small worms is more difficult when eggs are deposited throughout the plant. Also, as bollworm/budworm larvae increase in size, they attack fruit lower on the plant. Whole plant inspections are, therefore, necessary to detect larger larvae.

Two methods are presented below for assessing bollworm/budworm infestations. The Terminal/Square Inspection Method can be used when infestations are concentrated in the terminal (upper 1/3 of the plant). The Whole Plant Inspection Method can be used when eggs and worms are found throughout the plant.

Terminal/Square Inspection Method. Divide the field into four quadrants and examine 25 plant terminals, selected at random from each quadrant, for small larvae and eggs. Also, from each quadrant, examine 25 one-half grown and larger green squares for bollworms and bollworm damage. Squares should be selected at random and flared or yellow squares should not be included in the sample.

Before first bloom, insecticide application may be justified when 15 to 25 percent of the green squares are worm damaged. Once blooms are present, an insecticide application may be justified when 8 to 12 or more small larvae are present per 100 plant terminals and 5 to 15 percent of the squares or bolls are worm damaged. If worm numbers are high, it may not be appropriate to wait until the damage threshold of 5 to 15 percent square damage is reached.

If previous insecticide applications have eliminated natural enemies (see guidelines for scouting for predators on p. 7), fewer bollworms/tobacco budworms can be tolerated before economic damage occurs. If insecticides have been applied after first bloom and natural enemies eliminated, treatment may be justified when infestations reach or exceed four to five small worms plus eggs per 100 terminals and 5 percent of the squares and small bolls have been damaged by worms.

Microbial insecticides may be considered during the squaring period through the first 10 days of blooming if infestations average 12 or fewer small (less than 1/4 inch) bollworms per 100 terminals. Unlike conventional insecticides, microbial insecticides do not destroy predators and parasites (See Microbial Insecticides, p. 14).

Whole plant inspection method. Divide the cotton field into four or more manageable sections depending upon field size. Make whole plant inspections of five randomly chosen groups of three adjacent cotton plants in each section. Count the number of eggs, worms and key predators per acre using the following formula:

 The number of plants per acre is calculated from counts of plants on at least 10 feet of row in four locations in the field. The number of row feet per acre (See Monitoring Cotton Fruiting Rate) divided by the number of row feet examined multiplied by the number of plants counted equals the plants per acre.

Treatment may be justified when counts average 4,000 to 8,000 small worms or more per acre. A range of treatment thresholds is provided under both the Terminal and Whole Plant Inspection method because many factors in addition to density of larvae determine the need to treat with insecticides for bollworms/budworms. One of these factors is the number of predatory insects and spiders which feed on bollworm/budworm eggs and small larvae. If previous insecticide treatments have eliminated these beneficial insects, then a lower treatment threshold should be considered. However, if two or more key bollworm predators are found for each small worm, control measures may not be needed or a microbial insecticide may be considered (See Microbial Insecticides, p. 14). The number of bollworm/budworm eggs can also be considered along with worm densities in making treatment decisions. The treatment threshold will also vary according to the ability of the individual scout to locate small larvae, the age structure of the infestation, the stage of crop growth, the percent fruit set, the cost of insecticide treatment, the duration of the infestation (1 to 2 weeks vs. 3 to 4 weeks), the type of production system (high input/high yield or low input/low yield) and the market value of the crop.

Bt transgenic cotton management. Research trials evaluating the Bollgard^™ transgenic Bt gene technology have determined it to be highly effective against tobacco budworms. Bollgard^™ cottons are also effective against the cotton bollworm, but under heavy pressure from this species insecticide treatment may be needed.

The entire plant should be searched for tobacco budworm and bollworm larvae and injury. A proper sample includes squares, white blooms, pink blooms, bloom tags and bolls. Scouting intervals should be reduced to 3 to 4 days during periods of increasing bollworm egg laying, especially during peak bloom. Treatment should not be triggered by the presence of eggs alone. Hatching larvae must first feed on the cotton plant to receive a toxic dose. Treatment with foliar insecticides for tobacco budworm or bollworm should be considered when 4,000 to 8,000 larvae per acre larger than 1/4 inch are present (based on a population of 40,000 to 60,000 plants/acre) or when 8 to 12 larvae larger than 1/4 inch per 100 plants are present and 5 to 15 percent of the squares or bolls are worm damaged.

As with non-Bt cotton, a range of treatment thresholds is provided since many factors in addition to density of larvae and square damage determine the need to treat Bt cotton with insecticides. Many of these factors are the same as those listed above for non-Bt cotton. As in non-Bt cotton, predators and parasites are very important in reducing the numbers of eggs and larvae and they compliment the control provided by these varieties.

The use of a non- Bt cotton refuge is a requirement for planting Bt cotton and is an important component of resistance management ( Refer to L-5169, "Bt Cotton Technology in Texas).

Lygus bugs can continue to damage the late-season crop. Use the same sampling techniques and chemical control suggestions given in the previous section.

Management and decision making. Begin treatment when lygus bug counts exceed 20 to 30 per 50 sweeps (count nymphs as two) in fields where plants failed to retain squares and set bolls normally during the first 4 to 5 weeks of fruiting.

The cotton aphid is the most common aphid infesting cotton during mid- and late season. Aphids usually are found on the undersides of leaves, on stems, in terminals and sometimes on fruit. Heavy and prolonged infestations can cause leaves to curl downward and older leaves to turn yellow and shed, squares and small bolls to shed, and bolls to open prematurely, resulting in incomplete fiber development.

Honeydew excreted by the aphids can drop on fibers of open bolls. A black, sooty fungus sometimes develops on honeydew deposits. Fiber from such bolls is stained, sticky and of lower quality, resulting in difficult harvest, ginning and yarn spinning. Natural control by unfavorable weather, predators, parasites and pathogens can be effective in holding populations below damaging levels. Sometimes aphid numbers increase to moderate or heavy levels and then decline for no apparent reason.

Management and decision making. Although high populations can develop prior to bloom, most economically damaging infestations generally develop later in the season during the blooming period. Fields should be scouted twice per week since rapid increases in aphid numbers can occur in a short time. A total of 60 leaves divided between the top, middle and lower portion of the plant should be sampled from plants across the field to determine actual infestation levels. Insecticidal control of cotton aphids should be delayed until infestations exceed 50 aphids per leaf. Refer to the latest Cotton Aphid Task Force Suggestions for further management information. These are available at the county Extension office.

Cutworms may damage cotton during the seedling stage and control will be necessary if stands are threatened. The economic threshold is a matter of judgment. Keep fields as weed free as possible 6 weeks before planting to minimize cutworm problems. Destroy (with tillage or herbicides) cover crops at least 6 weeks before planting. Insecticide sprays or baits are recommended for band application over the drill. If the ground is dry, cloddy or crusty at the time of treatment, control may not be as effective as in moist soil.

Beet armyworm eggs are laid on both leaf surfaces in masses covered by a whitish, velvety material. Young beet armyworms "web up" and feed together on leaves, but eventually disperse and become more solitary in their feeding habits. Early-season infestations feed on leaves and terminal areas. Occasionally they destroy the plant terminal, causing extensive lateral branch development and delayed maturity. Larvae skeletonize leaves rather than chewing large holes in them. Damaging infestations sometimes develop late in the season when beet armyworms also feed on terminals, squares, blooms and bolls. Several factors can contribute to these late season beet armyworm outbreaks. These factors are: mild winters (e.g., absence of prolonged freezing temperatures); late planting; delayed crop maturity; heavy early season organophosphate or pyrethroid insecticide use; prolonged hot, dry weather conditions; presence of beet armyworms prior to bloom; and weather conditions that support long-distance migration. Additional characteristics of high risk fields that consistently appear to fit a pattern for developing beet armyworm problems are: sandy and droughty soils; skip-row planting; fields with skippy, open canopies; drought stressed plants; and fields infested with pigweed. The likelihood of a heavy outbreak increases as more of these factors occur in a given location. However, when beet armyworm populations are high all fields are susceptible. When beet armyworms begin to damage fruit, control may be justified. Infestations usually are spotty within a field, and careful scouting is necessary to determine the need for, and field area requiring, control. Beet armyworms longer than ˝ inch may be difficult to control.

Management and decision making. Scout the field using the Whole Plant Inspection Method described in the bollworm and tobacco budworm section. Early Detection Threshold (Hatching Egg Masses); from initiation of squaring to cutout, if 2 "active hits" (i.e., recently hatched egg masses with actively feeding larvae) are detected per 100 row feet and conditions are optimal for a beet armyworm outbreak, treatment should be considered. Hits can be detected by observing plant leaves by walking along a row for a measurable distance. Some insecticide labels refer to active hits per 100 row feet. Remedial Threshold; for advanced infestations during mid season is when small worm counts exceed 20,000 per acre and at least 10 percent of the plants examined are infested, control may be warranted. Refer to Management Guidelines for the Beet Armyworm in Cotton for further management information. These are available at the county Extension office.

Spider mites infest the undersides of leaves, where they remove the sap from the plant and cause the leaves to discolor. They may also infest bracts of squares and bolls, causing the bracts to desiccate and squares or small bolls to shed. Severe infestations can defoliate the cotton plant. Mite infestations most often occur in spots and in field margins. Increased spider mite populations usually follow multiple applications of insecticides for other pests, since insecticides destroy natural spider mite predators.

Management and decision making. Treat when mites begin to cause noticeable leaf damage. Spot treatment of fields is encouraged when infestations are restricted to small areas. Two applications at 5-day intervals may be required for acceptable control. In certain locations, some mite species are highly resistant to miticides and are difficult to control with available materials.

Moths of these species lay eggs singly, mainly on the lower surfaces of leaves. Larval feeding damage is characterized by leaf ragging or large holes in the leaves. Larvae often are killed by a disease before economic foliage loss occurs.

Management and decision making. An economic threshold for these pests has not been established. As a general guideline, treat when 10 percent of the "key leaves" are infested with worms. The key leaf is the third one down the main stem from the tip (usually the highest leaf on the plant).

Several species of stink bugs feed on squares and bolls. Feeding on bolls may cause boll shed and/or seed damage, lint staining and yield reduction.

Management and decision making. Examine 6 row feet of cotton in several locations in the field. When there is an average of one or more stink bugs per 6 feet of row, feeding can cause excessive loss of squares and small bolls and may stain lint. Stink bugs often are clumped near field margins. Spot treatment provides effective control when this situation exists.

Second through fifth instar stink bugs and adults all cause damage to bolls. Fourth and fifth instars can cause the same level of damage as adults.

Grasshoppers

A number of grasshopper species are occasional cotton pests. They generally move into fields from adjacent fence rows, ditch banks and field margins.

Management and decision making. Twenty or more grasshoppers per square yard in crop mar-gins or ten or more per 3 row feet in the field are suggested treatment levels if there are signs that the species is feeding on cotton.

Fall armyworm, yellow striped armyworm, southern armyworm, cotton square borer and salt marsh caterpillar rarely cause economic damage.

Management and decision making. Economic thresholds have not been established for these pests. Control is a matter of individual judgment.

In areas where early-season pests such as thrips, aphids and spider mites consistently damage young cotton each year, preventive systemic insecticides are sometimes used instead of post-emergence sprays. In choosing either approach to early-season pest control, key factors to consider include acreage, yield potential, available equipment and labor, knowledge of cotton pests and beneficial species, difficulties in getting a stand, drought tendencies, etc. Both the limitations and advantages of systemics used at planting should be evaluated carefully before choosing their use over post-emergence insecticides.

These insecticides effectively reduce numbers of bollworm and tobacco budworm eggs. Because large numbers of eggs often fail to produce economically damaging worm infestations, insecticidal control of eggs alone is not recommended. Environmental factors such as hot, dry weather can significantly reduce field levels of eggs. Some other important natural control factors include predaceous insects, spiders and parasitic wasps. Natural egg control can vary greatly between fields and times of the season. Often, high numbers of sterile eggs are found. If larval infestations exceed suggested treatment levels and large numbers of eggs are present, the addition of an ovicide to the larvicide may be justified to enhance overall control.

Microbial products which are natural pathogens of the bollworm and the tobacco budworm are commercially available as preparations of Bacillus thuringiensis (Bt). Field studies indicate that microbials are best suited for square protection. They are slow acting and should be used only against infestations of worms during the squaring period through the first 10 days of blooming. They are not suggested for use after that point. Microbials are effective against worm numbers up to 12 per 100 plants (6,000 per acre). They do not destroy beneficial arthropods (predators and parasites), a characteristic which sets them apart from conventional insecticides. When beneficial arthropod populations are absent, other insecticides provide more consistent control.

Treat fields in which most of the larvae are not more than 1/4 inch long. Infestations of larger worms should not be treated with microbials. Maximum effectiveness with Bt requires precise sampling of cotton plants during the fruiting period. Sampling should be conducted at least twice a week while squares are developing. Apply microbials with ground equipment at the rate of 5 to 15 gallons of liquid per acre, or by air using 2 to 5 gallons per acre. Good coverage is essential.

Pollination is extremely important in producing many seed crops such as alfalfa, clover and vetch. Honey bee pollination also is critical in the production of cucurbits throughout the state, and supplements native pollinators. The role of honey bees and wild pollinators in contributing to increased yield and fiber length of cotton is unclear. The importance of insect pollinators in the production of hybrid cottons is well recognized, however. Where pollinating insects are required for flower fertilization, the crop producer, insecticide applicator and beekeeper should cooperate closely to minimize bee losses. The following guidelines will reduce bee losses:

1. Apply insecticides, if practical, before bees are moved into fields or adjacent crops for pollination. When bees are in the vicinity, evening applications after bees have left the field are less hazardous than early morning applications.

2. Where insecticides are needed, consider their toxicity. "Highly toxic" insecticides include materials that kill bees on contact during application or for several days following application. Insecticides categorized as "Moderately toxic" or "Relatively non-toxic" should be applied in late evening or early morning when bees are not foraging.

3. To prevent heavy losses of bees, avoid drifting or spraying any insecticide directly on colonies. Bees often cluster on the fronts of their hives on hot evenings. Pesticide drift or direct spray at this time generally results in high levels of mortality.

The information and suggestions included in this publication reflect the opinions of Extension entomologists based on field tests or use experience. Our management suggestions are a product of research and are believed to be reliable. However, it is impossible to eliminate all risks. Conditions or circumstances which are unforeseen or unexpected may result in less than satisfactory results even when these suggestions are used. Texas Cooperative Extension will not assume responsibility for such risks. Such responsibility shall be assumed by the user of this publication.

Suggested pesticides must be registered and labeled for use by the Environmental Protection Agency and the Texas Department of Agriculture. The status of pesticide label clearances is subject to change and may have changed since this publication was printed. County Extension agents and appropriate specialists are advised of changes as they occur.

The USER is always responsible for the effects of pesticide residues on his livestock and crops, as well as problems that could arise from drift or movement of the pesticide from his property to that of others. Always read and follow carefully the instructions on the container label. For additional information, contact your county Extension staff or write the Extension Entomologist, Entomology Department, Texas A&M University, College Station, Texas 77843, (979) 845-7026.

The Endangered Species Act is designed to protect and to assist in the recovery of animals and plants that are in danger of becoming extinct. In response to the Endangered Species Act, many pesticide labels now carry restrictions limiting the use of products or application methods in designated biologically sensitive areas. These restrictions are subject to change. Refer to the Environmental Hazards or Endangered Species discussion sections of product labels and/or call your local county Extension agent or Fish and Wildlife Service personnel to determine what restrictions apply to your area. Regardless of the law, pesticide users can be good neighbors by being aware of how their actions may affect people and the natural environment.

The Worker Protection Standard (WPS) is a set of new federal regulations that applies to all pesticides used in agricultural plant production. If you employ any person to produce a plant or plant product for sale and apply any type of pesticide to that crop, WPS applies to you. The WPS requires you to protect your employees from pesticide exposure. It requires you to provide three basic types of protection: you must inform employees about exposure, protect employees from exposure, and mitigate pesticide exposures that employees might receive. The WPS requirements will appear in the "DIRECTIONS FOR USE" part of the pesticide’s label. For more detailed information, consult EPA publication 735-B-93-001 (GPO #055-000- 0442-1) The Worker Protection Standard for Agricultural Pesticides — How to Comply: What Employers Need to Know, or call Texas Department of Agriculture, Pesticide Worker Protection Program, (512) 463- 7717.

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

Educational programs conducted by the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age or national origin.

Return to top of page

Return to Departmental Home Page

Last modified: April 11, 2002