Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas 2003 Contents Page Pest Management Principles

E-6 3-03

Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas 2003 Contents Page Pest Management Principles ...... 3 Insecticide Resistance Management ...... 3 Biological Control ...... 3 Bt Transgenic Cotton ...... 4 Crop Management ...... 4 Irrigated Production ...... 4 Dryland Production ...... 5 Monitoring Cotton Growth ...... 5 Early Stalk Destruction and Field Clean-up ...... 6 Stalk Destruction Laws ...... 6 Management Decisions...... 6 Scouting Decision ...... 7 Early-Season Pests ...... 7 Thrips ...... 8 Cotton Fleahopper ...... 8 Overwintered Boll Weevil ...... 8 Mid-Season and Late-Season Pests ...... 9 Bollworm and Tobacco Budworm...... 10 Boll Weevil ...... 11 Aphids ...... 12 Pink Bollworm ...... 12 Beet Armyworm ...... 13 Occasional Pests ...... 13 Grasshoppers ...... 13 Lygus Bugs ...... 13 Stink Bugs ...... 14 Cabbage Looper ...... 14 Spider Mites ...... 14 Other Pests ...... 14 Systemic Insecticides at Planting ...... 14 Limitations of Systemics ...... 15 Advantages of Systemics...... 15 Ovicides ...... 15 Microbial Insecticides ...... 15 Diapausing Boll Weevil Control ...... 15 Protecting Bees from Insecticides ...... 16 Policy Statement for Making Pest Management Suggestions ...... 16 Endangered Species Regulations ...... 16 Worker Protection Standard ...... 16 Additional References ...... 17

For recommended insecticides refer to E-6A, "Suggested Insecticides for Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas 2003" at the following web sites: http://insects.tamu.edu/extension/ag_and_field.html or http://tcebookstore.org Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas Mark A. Muegge, Brant A. Baugh, James F. Leser and Thomas A. Doederlein*

A committee of state and federal research personnel Insecticide Resistance Management and Extension specialists meets annually to review cotton pest management research and management Experience has shown that reliance on a single class guidelines. These guidelines are directed toward of insecticides that act the same way may cause pests maximizing profits for the Texas cotton producer by to develop resistance to the entire group of insecti- optimizing inputs and production. cides. A good strategy to help avoid pest resistance is to rotate the use of insecticide groups, taking advan- tage of different modes of action. Such insecticide Pest Management Principles management should delay the development of resis- The term “pest management” applies to a philosophy tance and also provide better overall insect control. used in the design of insect, mite, disease and weed Insecticides with similar chemical structures affect pest control programs. It encourages the use of the insects in similar ways. For example, pyrethroids most compatible and ecologically sound combination of (including esfenvalerate, cypermethrin, bifenthrin, available pest suppression techniques. These manage- cyfluthrin, cyhalothrin, deltamethrin, tralomethrin and ment techniques include: cultural control, such as zeta-cypermethrin) all act on an insect’s nervous manipulation of planting dates and stalk destruction; system in the same way. Other types of insecticides crop management practices, such as variety selection such as organophosphates (methyl parathion, and timing of irrigation; biological control, involving dicrotophos) or carbamates (thiodicarb) also affect the conservation of existing natural enemies; host plant insect’s nervous system, but in a different way than do resistance; and the wise use of selective insecticides the pyrethroids. and rates to keep pest populations below economically damaging levels. Biological Control Major factors to be considered when using insecticides include protecting natural enemies of cotton Insect and mite infestations are often held below pests, possible resurgence of primary pests, increased damaging levels by weather, inadequate food sources numbers of secondary pests following applications and and natural enemies such as disease, predators and pest resistance to insecticides. Therefore, insecticides parasites. It is important to recognize the impact of should be applied at the proper rates and used only these natural control factors and, where possible, when necessary, as determined by frequent field inspec- encourage their action. (See B-6046, “Guide to the tions, to prevent economic losses from damaging pests. Predators, Parasites, and Pathogens Attacking Insect and Mite Pests of Cotton,” Texas Cooperative Exten- The pest management concept rests on the assump- sion.) tion that pests will be present to some degree in a production system, and that at some levels they may not Biological control is the use of predators, parasites cause significant losses in production. The first line of and disease to control pests. Important natural en- defense against pests is prevention through the use of emies in cotton include minute pirate bugs, damsel good agronomic practices or cultural methods which bugs, big-eyed bugs, assassin bugs, lady beetles, are unfavorable for the development of pest problems lacewing larvae, syrphid fly larvae, spiders, ground (discussed below). Properly selected control measures beetles and a variety of tiny wasps that parasitize the should be taken only when pest populations reach eggs, larvae and pupae of many cotton pests. levels at which crop damage suffered could result in Biological control includes the conservation, impor- losses greater than the cost of the treatment. This tation and augmentation of natural enemies. It is an potentially injurious population or plant damage level, environmentally safe method of pest control and is a determined through regular field scouting activities, is component of integrated pest management programs called an economic threshold or action level. in cotton. The Texas A&M University System is fully Precise timing and execution of each production committed to the development of pest management operation is essential. In short, pest management tactics which use biological control. strives to optimize rather than maximize pest control Existing populations of natural enemies are con- efforts. served by avoiding the use of insecticides until they are needed to prevent the development of economi- *Extension entomologist, Extension agent—IPM, Extension entomolo- cally damaging pest infestations. Insecticide impact gist, and Extension agent—IPM, The Texas A&M University System. can also be minimized by using insecticides that are

3 more toxic to the target pests than to the natural In all cases, economic thresholds used for Bt cottons enemy. Classical biological control is the importation should be the same as those used for non-Bt cottons, of natural enemies from other countries. This method but should be based on larvae larger than 1/4 has been effective where an exotic pest has entered inch and damage, not on eggs or early instar Texas without its incumbent natural enemies, or to larvae. For additional information on Bt cotton refer augment natural enemies of native pests. to B-6107, “Bt Cotton Technology in Texas: A Practical Augmentation involves the purchase and release of View,” available from your county Extension office. natural enemies on a periodic basis. The most notable commercially available natural enemies include the Crop Management egg parasite Trichogramma, and the predators lady beetles and lacewings. Although the control of both Irrigated Production bollworms and tobacco budworms by the release of Plan and conduct production practices to achieve commercially reared Trichogramma wasps is theoreti- early crop maturity in order to escape late-season cally possible, researchers have not been able to insect attack and population buildup of insect pests. consistently achieve the level of parasitism necessary Production inputs should be directed toward maxi- to reduce infestations below economically damaging mum crop profit instead of maximum crop yield. levels. Multiple Trichogramma releases at high rates ranging from 50,000 to 150,000 parasitized eggs per Crop management practices that have an impact on acre were used in these studies. There are currently insect pest numbers and crop damage are: no economic thresholds established for augmentative • Varietal selection (short-season or full-season releases of Trichogramma for bollworm/budworm varieties). Short-season varieties usually mature control in cotton. Furthermore, parasite mortality earlier and escape late-season pest problems from insecticides used to control other pests in or which often occur on late-season varieties. around parasite release areas would limit the effective- • Uniform planting dates. Allow fields in an area ness of augmentative releases. to mature together. Pest infestations are pre- Research has shown that releasing large numbers of vented from developing in earlier planted fields lacewing larvae (30,000 or more per acre) can reduce and moving into later planted fields. bollworm infestations below damaging levels. How- • Plant population on irrigated cotton should range ever, these release rates are currently cost prohibitive from 35,000 to 65,000 plants per acre (2.5 to 4.5 because of the high production cost of rearing lace- plants per foot on 40-inch rows) in most areas. wings. The release of lacewing eggs has been less Larger plant populations can cause delayed crop successful and there is little information on the effi- maturity due to competition for water, nutrients cacy of releasing adult lacewings in cotton. There is and sunlight. Overcrowding may also contribute even less information about releasing either lady to undesirable stalk growth. beetles or lacewings for the control of economically damaging infestations of aphids. Because there is too • Amount of nitrogen fertilizer used and applica- little information about augmentation (when to apply, tion timing. Excessive or late nitrogen applica- what density should be applied, etc.), entomologists tions delay crop maturity, particularly when with Texas Cooperative Extension cannot provide coupled with late irrigation, and subject the crop guidelines for augmentation as a management tool in to intensified and prolonged attack by cotton cotton. bollworms, tobacco budworms, boll weevils and pink bollworms. • Weed control. Weeds limit yield by competing Bt Transgenic Cotton directly with cotton plants for water and nutri- Bt cottons are insect-resistant cultivars and one of the ents; they also attract various insect pests into first such agricultural biotechnology products to be cotton fields. released for commercial production. Insect resistance • Amount and timing of crop irrigations. Timing of in the Bt cottons was engineered by the introduction of irrigations often is more important than the total a bacterial gene that produces a crystalline toxin, amount of water applied. Water use by the which, in turn, kills feeding larvae of several cotton cotton plant is very low during the 35- to 40-day pests. period from seed emergence to the appearance of The toxin in Bollgard® cottons has excellent activity the first square. Water use increases rapidly with against tobacco budworm, pink bollworm, cotton leaf the appearance of the first square. Maximum perforator and European corn borer, and good activity water use is reached during peak bloom. As the against cotton bollworm, saltmarsh caterpillar and plant progresses toward maturity, water demands cabbage loopers. Under heavy infestation pressure, are reduced. supplemental insecticide treatment may be Flowering is the period of most rapid plant growth necessary for bollworm. Bt cottons provide some and development when more than half of the total suppression of beet armyworm and soybean looper, water is used. Excessive irrigation during this period and little or no control of fall armyworm or cutworm. may make plants more attractive to bollworm and

4 tobacco budworm moths because of additional vegeta- low, insecticides and other inputs such as fertilizers tive growth. Excessive vegetative growth can be should be based on realistic yield goals. checked by allowing sufficient depletion of available The yield potential of cotton planted after June 20 is water before each irrigation. Excessive water will greatly reduced; average yields can be expected only in delay crop maturity, thus increasing crop susceptibility those years when warm conditions extend well into to attack from bollworms, tobacco budworms, boll October. Because of the limited yield potential, addi- weevils and pink bollworms. tional benefits from the management of insects are also The final irrigation should be timed to provide limited. An insecticidal application can be expected to enough moisture to mature the bolls set during the first result in a positive economic return only when expected 4 weeks of boll production in upland and acala cotton, damage equals or exceeds the insecticide and applica- and to mature the bolls set during the first 6 weeks in tion cost. Pima cotton. Fruit produced as a result of late irriga- Information on cotton varieties that perform best tions not only adds little to final yield, but also delays under dryland conditions can be obtained from county the opening of mature bolls, increases crop susceptibil- Extension agents who annually conduct cotton variety ity to insects, induces boll rot and contributes to demonstrations. Short-season cottons fruit and mature defoliation problems. Late set bolls normally have a more rapidly than Delta-type varieties; consequently, poor probability of producing fiber and the lint pro- the short-season varieties are subject to insect damage duced from these bolls is generally of poorer quality for a shorter period of time and may escape the devel- because of immature fibers and insect damage. opment of large late-season insect populations. Crop irrigation should terminate at least 10 days Fertilization of dryland cotton should be based on a prior to a predicted peak in bollworm egg-laying. This soil test. will reduce plant attractiveness to bollworm and Plant dryland cotton so that there are 26,000 to budworm moths, lower field humidity to suppress egg 53,000 plants per acre (two to four plants per foot on hatch and limit the amount of young, tender growth available for newly hatched worms to feed on. 40-inch rows). Higher plant populations cause greater competition between plants for moisture and nutrients and can lead to increased pest damage. Dryland Production Severe bollworm problems can occur in either wet or The primary factor limiting dryland cotton produc- dry years; however, wet conditions, which favor succu- tion is the lack of adequate moisture prior to and lent growth, are generally more favorable for bollworm during the growing season. Due to the lack of moisture survival. Bollworms and aphids may become a problem or the formation of a hardpan, cotton plants may be following an insecticide application which destroys unable to develop an adequate root system. Dry beneficials. Insecticides should be applied only when conditions and moisture stress after cotton begins to necessary, as determined by frequent field inspection. fruit will cause the cotton plants to abort squares and small bolls, often reducing or completely negating any Monitoring Cotton Growth potential yield increase obtained from pest control. The amount of moisture in the soil profile at planting Early fruiting is desirable and facilitates early crop appears to be the most accurate predictor of potential maturity. Frequent monitoring gives a good indication yield. Each insecticidal control decision must be made of crop set. Problem fields often can be detected early based on the anticipated yield. Because the yield if growth and fruiting habits are accurately monitored, potential of dryland cotton is generally moderate to although the cause of a problem may not be immedi- ately evident. To monitor fruiting levels, mark a point on a row of plants and count 100 consecutive 1/3 -grown (1/4 inch in diameter) or larger green squares; record the number of row feet required to gain that count. Record also the number of bolls observed. Later in the season, when bolls are more numerous, count 100 consecutive 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 recorded to gain a count of 100 consecutive squares or bolls into the number of row feet per acre (13,068 for 40-inch rows and 13,756 for 38- inch rows) and multiply by 100:

Bolls and/or squares per acre = 13,068 or 13,756 x 100 No. row feet recorded for 100 consecutive bolls or squares

5 To monitor the squaring rate, count fruiting sites and harvested until frost, stalks may be left standing in the all squares on at least ten plants from each of four re- field except in areas where the pink bollworm is a presentative areas in the field. Fruiting usually begins problem. Stalks should be shredded and plowed on nodes 6 to 9 depending on variety and environmen- under to a depth of 6 inches in areas of pink bollworm tal conditions. Node 1 is the cotyledonary node (seed infestation. Green or cracked bolls left at the ends of leaves). To calculate percent square set, divide the rows should be destroyed to reduce pink bollworm number of small squares counted by the number of populations. Where cotton is harvested before a fruiting sites recorded and multiply by 100. In normal killing frost, plants should be shredded to prevent fields, 75 percent or more of the small squares are regrowth which can provide squares for weevils to retained during the first 3 to 4 weeks of squaring. feed on and allow them to successfully overwinter. After moisture, the most important factor in develop- The addition of 0.5 lb. methyl parathion or 0.25 lb. ment of squares and bolls is temperature. Researchers azinphosmethyl (Guthion®) to phosphate-type defoli- have devised a way to describe and measure the ants has proven effective in reducing overwintered relationship between cotton development and tempera- boll weevils. Do not add methyl parathion or ture — the heat unit concept or DD60 (degree days azinphosmethyl to chlorate-type defoliants because of using 60 degrees F). Heat units measure the amount of the potential fire hazard. useful heat energy a cotton plant accumulates each day, each month, and for the season. The plant must accu- mulate a specified level of heat units to reach each Stalk Destruction Laws development stage and to achieve complete physiologi- Upon request and petition of Texas Cotton Produc- cal maturity. ers, the Texas Legislature passed the Cotton Pest Several systems have been developed to calcuate Control Law in an effort to combat the boll weevil and heat units, but the most universal approach is to use pink bollworm. This law, which is enforced by the the formula ((Degrees F Maximum + Degrees F Mini- Texas Department of Agriculture, requires producers mum) ÷ 2) - 60. in a regulated county to culturally manage pest populations using habitat manipulations by planting and destroying cotton within an authorized time Cotton development by calendar days and heat units. period. Appointed producers, who are members of Calendar days Accumulated heat local pest management zone committees, have estab- Growth Mean Range units (DD60's from lished a series of cotton planting and stalk destruction interval planting required*) deadlines for all producers in each regulated county.

Planting to: The battle against pink bollworms has been ex- Stand establishment 7 5 - 13 78 tremely successful. Because farmers have adhered to First true leaf 16 11 - 25 authorized planting and stalk destruction deadlines Squaring 36 29 - 41 526 over the past years, pink bollworm populations in 1/3-grown square 44 36 - 49 most of the state have been reduced to levels that First bloom 61 45 - 81 1064 don’t cause major economic damage. Boll weevil Peak bloom 79 59 - 102 First open boll 96 88 - 106 1641 population control through stalk destruction efforts 95% mature bolls 146 129 - 163 2271 has been significant but progress has been slower. Strict adherence to the established deadlines is critical Boll development: to the success of boll weevil management. Fiber length established: First 18-45 days Fiber micronaire and strength determined: Next 20-60 days Management Decisions

*Calculated by the formula: Control measures are needed when a pest population DD 60 = High daily temperature + low daily temperature - 60 reaches a level at which further increases would result 2 in excessive yield or quality losses. This level is known For each day in which the result is a positive number, heat units are accumulated. as the “economic threshold” or treatment level. The For example, if the high for the day is 90 and the low 60, then 90 + 60 = 150 ÷ 2 = relationship between pest level, amount of damage, and 75; 75 - 60 = 15; so 15 heat units would be accumulated for the day. This total would ability of the cotton plant to compensate for insect dam- be added to those accumulated each day since planting to get accumulated heat units. age is greatly influenced by crop phenology and sea- sonal weather. The economic threshold is not constant but varies with factors such as the price of cotton, the Early Stalk Destruction and Field Clean-Up cost of control, and stage of plant development. Early harvest and stalk destruction are among the When a cotton field is properly scouted, accurate most effective cultural and mechanical practices for and timely decisions can be made to optimize control managing overwintering boll weevils if done on an efforts while minimizing risk. Fields should be in- areawide basis. These practices reduce habitat and spected every 3 to 7 days using the scouting proce- food available to the boll weevil, pink bollworm, dures described in this guide for the various pests. bollworm and tobacco budworm. When cotton is not

6 Scouting Decisions predator densities averaging 0.5 per plant. More samples would be required when predator densities are Regular field scouting is a vital part of any pest lower and fewer samples are required when predator management program because it is the only way densities exceed 0.5 per plant. reliable information can be obtained to determine if and when pest numbers reach the economic threshold. Number of samples required to estimate densities of preda- Scouting should involve more than just “checking tors with the same level of precision when sampling with a bugs.” Scouting determines the insect density and beat bucket, sweep net or visually searching the plant. damage levels through the use of standardized, repeat- able sampling techniques. Scouting should also Beat Sweep Visual Predator bucket net search include monitoring plant growth, fruiting, weeds, diseases, beneficial insect activity, and the effects of Pirate bug adults 31 51 129 implemented pest suppression practices. Pirate bug nymphs 48 262 255 Scouting for predators. Predatory insects and Crab spiders 19 58 356 spiders can sometimes maintain densities of bollworms, Lady beetles 8 20 68 aphids and other pests below economic levels. Knowing Big-eyed bug nymphs 22 17 130 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 Refer to B-6046, "Guide to the Predators, Parasites the producer to those fields that are at risk of pest and Pathogens Attacking Insect and Mite Pests of outbreaks because of low predator densities. Sampling Cotton" (see p. 17 to order) for information on identify- predators can also measure the impact of previous ing common predatory insects and spiders in cotton. insecticide applications on predator numbers. Scouting for pests. The following general discus- The number of predatory insects and spiders in sion briefly reviews the insect pests of cotton (for more cotton can be rapidly and accurately determined by detail see B-933, "Identification, Biology and Sampling the beat bucket method. This method is more reliable of Cotton Insects"). The insect pests are discussed as and faster than searching the plant for predators. The they normally would occur throughout the cotton beat bucket method uses a common white, 5-gallon production season. Growers should check fields at plastic bucket or pail about 14 inches deep and 10 least once and preferably twice a week to determine inches in diameter. To use the beat bucket, carefully the species present, the pest density and the amount of approach the sample plant and grasp the stem near the damage. Most pests can be monitored by visually base of the plant. While holding the bucket at a 45- checking the terminal and by making whole plant degree angle to the ground, quickly bend the plant into inspections. However, some pests, such as plant bugs the bucket so that the terminal and as much of the (Lygus spp.), are more reliably sampled using a drop plant as possible are inside the bucket. Still holding the cloth. The drop cloth method uses an off-white cloth stem near the base of the plant, rapidly beat the plant measuring 36 x 42 inches (on 40-inch rows). Staple a against the side of the bucket 12 to 15 times during a thin strip of wood, approximately 1 inch wide, to each 3- to 4-second period. This dislodges predators from short side of the cloth. Select a random site in the field the plant so that they fall into the bottom of the and unroll the cloth from one row over to the next bucket. Remove the plant and hold the bucket upright row. Mark off 18 inches on each row bordering the to prevent predators from escaping. Quickly take one cloth and vigorously shake all the plants within that step, sample a second plant and then another step and area. Two 1.5-row-foot sections (3 feet total) will be sample a third plant down the row. Banging the side of sampled simultaneously for insects. Count the number the bucket with the hand will knock down predators of lygus bug adults and nymphs that fall on the cloth. crawling up the side of the bucket while sampling. Repeat the process in at least 20 locations in the field After the third plant is sampled, record the number of (60 feet of row sampled). If the results show that bollworm predators (pirate bugs, spiders, big-eyed populations are close to threshold levels, or if the field bugs, lacewing larvae) and others of interest (lady is very large (more than 100 acres), sample more areas beetles, etc.) captured in the bucket. Remove and to increase confidence in the results. 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 Early-Season Pests encourage predators that are playing dead to begin The period from plant emergence to first 1/3-grown moving and become apparent. The bucket must be squares requires about 5 to 6 weeks. The 1/3-grown kept clean so that the predators are easily seen. square is approximately 1/4 inch in diameter. Major The table below shows the number of samples, from pests during this crop development period include actual field data, required to estimate predator densities thrips, cotton fleahoppers, plant bugs and overwin- with the same level of precision when sampling with tered boll weevils. the beat bucket (three plants per bucket), a sweep net (five sweeps per sample) or visually searching the plant. The sample sizes in this example are calculated for

7 Cotton Square Diameter plants reach the 5- to 7-true-leaf stage, or when plants begin to square. 1/16-inch 3/16-inch 1/4-inch Cotton Fleahopper Pinhead Matchhead 1/3-grown Adult fleahoppers are about 1/8 inch long and pale green. Nymphs resemble adults but lack wings and are light green. They Thrips move very rapidly when disturbed. Adults move into cotton from weed hosts when cotton begins Thrips are slender, straw colored to square. Both adults and nymphs suck sap from the insects about 1/15 inch long, with tender portion of the plant, including small squares. piercing and sucking mouthparts. Pinhead size and smaller squares are most susceptible Adults are winged and capable of to damage. drifting long distances in the wind. Thrips attack leaves, leaf buds and very small squares and may cause Management and decision making. The decision a silvering of the lower leaf surface, deformed or to apply insecticide should be based on the number of blackened leaves, terminal loss and square loss. Under fleahoppers present, the squaring rate and the percent some conditions, heavy infestations may reduce stands, square set. If conditions are conducive to the rapid stunt plants and delay fruiting and maturity. Thrips build up of cotton fleahoppers in alternate hosts, damage is most evident during cool, wet periods when scouting intervals should be shortened (i.e., monitor small cotton is growing slowly. Thrips damage often is fields every 3 to 4 days). During the first week of further compounded by plant damage resulting from squaring, the economic threshold is 25 to 30 rain, wind, blowing sand and diseases. Under favor- cotton fleahoppers per 100 terminals combined able growing conditions, cotton can sometimes recover with less than 90 percent square set. In the completely from early thrips damage. In many areas second week of squaring, the economic threshold thrips are considered minor cotton pests. Thrips is 25 to 30 cotton fleahoppers per 100 terminals problems are more prevalent in areas with large winter combined with less than 85 percent square set. wheat acreages and where producers plant prior to late Starting with the third week of squaring up to May or early June. Research has demonstrated that first bloom, the economic threshold is 25 to 30 cotton varieties with hairy leaves are less injured by cotton fleahoppers per 100 terminals combined thrips than smooth-leaf varieties. with less than 75 percent square set. Management and decision making. In areas In cotton planted after May 15, treatment decisions with a history of frequent, heavy thrips infestations, should be made during the first week of squaring, if the use of systemic insecticides should be seriously possible, to avoid a potential bollworm outbreak considered. Research has shown that the application resulting from the destruction of beneficial insects and of foliar sprays after significant thrips damage has spiders. As plants increase in size and fruit load, occurred generally does not result in increased yields. larger fleahopper populations can be tolerated without Where postemergence sprays are to be used, fields yield reduction. In most years treatment is rarely should be scouted as often as twice a week as cotton justified after first bloom. However, occasionally, emerges. Thrips can migrate in heavy numbers from when cotton plants do not set an adequate square load adjacent weeds or crops, especially small grains, and during the first 3 weeks of squaring, fleahoppers can cause significant damage within a few days and prior prevent the square set that is needed for an adequate to the appearance of true leaves. crop. Early infestations often reduce yield more than later infestations. Thrips often infest the folded small leaves Overwintered Boll Weevil of the plant terminal and are difficult to count unless Emerging overwintered boll weevils the terminal area is dissected. This is especially true usually move relatively short distances during rainy, windy conditions. The decision to apply from hibernation sites and usually are insecticide should be based on the number of thrips confined to small areas in fields adjacent present and the stage of plant development. The to good overwintering habitat. Overwintered weevil number of thrips per plant to use as a treatment level emergence begins during early spring and generally increases as plants add more leaves. Control may be peaks during late May and early June. However, justified when the average number of thrips significant emergence can continue into early July in counted per plant is equal to the number of true some years. The adult weevil is about 1/4 inch long, leaves present at the time of inspection. One thrips grayish brown, and has a prolonged snout with per plant should be used as the treatment level from chewing mouthparts at its tip. The presence of two plant emergence, through the cotyledon stage, to the distinct spurs on the lower part of the first segment first true leaf. Inspections should begin once cotton of the front leg will distinguish the boll weevil from has reached approximately 50 percent stand emer- other weevils with which it might be confused. gence. Insecticidal control is rarely justified once

8 Weevil colonization in cotton is closely related to early squaring indicates the size of the overwintering the fruiting of the plant, with the greatest numbers population and the need for one or more insecticide of overwintered weevils entering cotton fields after applications. squares are present. Therefore, the extent of over- Pheromone traps must be kept operational and wintered weevil infestation depends on the size of inspected regularly to be reliable. Rain, windy condi- the emerging weevil population and the availability tions and cool temperatures will reduce weevil re- of squaring cotton. Thus, early-planted cotton and sponse to pheromone traps. Therefore, if adverse fields adjacent to ideal overwintering habitat are weather conditions are present during the week of first much more likely to have significant weevil infesta- square, the average trap catch for the previous week tion than cotton planted later in the season or fields should be considered in determining the need to treat. farther away from good overwintering habitat. In Pheromone trap data may not be reliable after 25 areas where a uniform delayed planting date is recommended, volunteer cotton should be destroyed percent or more of the cotton in an area has begun to square or after 1/3-grown squares are present in a field as early as possible. around which the traps are located. Trap data are most Management and decision making. In weevil reliable in areas using uniform planting dates. infested areas, uniform planting of cotton on a commu- Field inspection method. Fields should be nity-wide basis after mid-May will often significantly observed very closely when pinhead size squares begin reduce weevil infestations. When fruiting cotton is not available for feeding, the life span of newly emerged to appear. Inspect at least 100 plants for adult boll weevils. If one or more weevils are found per 100 weevils is relatively short. Therefore, delayed, uni- plants checked or four weevils per 100 feet of row form planting of cotton increases suicidal emergence of overwintered weevils. monitored (about 530 weevils per acre) in cotton which was planted after mid-May, apply insecti- The need for insecticide applications to suppress cide just prior to or when first squares reach 1/3- overwintered boll weevils can be determined by: 1) grown stage. pheromone trap collections (Trap Index Method); 2) Overwintered boll weevil control is designed to Field Inspection Method; or 3) a combination of both destroy adult weevils in the field before they deposit methods. eggs in squares. It is also designed to keep the F1 (first Trap Index Method. Boll weevil pheromone traps in-season) weevil generation below the treatment level, should be placed along field margins near favorable thereby avoiding the treatments at a time when boll- overwintering habitat or near areas of the field with a worm outbreaks are more likely to occur (late July to history of early infestations. For fields up to 100 acres early August). If field or trap inspections indicate that in size, at least four to five traps should be used. weevils are still entering the field following the first Pheromone traps should be in operation several weeks insecticide application, an additional one or two before the first squares appear in cotton. The treat- applications may be needed. The first application ment decision is based on the “Trap Index” and scout- should be made just before the earliest squares are 1/3- ing information. Inspect traps weekly and determine grown with additional applications following at 5-day the average number of weevils caught per trap each intervals. week for each field monitored. Record numbers for Applications should be terminated as soon as future reference. Weevils entering fields shortly before and during early squaring are the most impor- possible after the first 1/3-grown square stage to allow beneficial insects and spiders time to reestablish. tant from the standpoint of potential infestation. There is always a risk of increased bollworm activity Determine the average number of weevils captured for the week that the first squares (pinhead to matchhead where these treatments are made within 10 days of bloom. size) appear. This will be the Trap Index. The number of weevils captured in traps prior to and during the Mid-Season and Late-Season Pests Trap Index Decision Mid-season is the 6-week fruiting period following 1 or fewer weevils per trap Do not treat. the appearance of the first 1/3-grown squares. Proper per week crop management and frequent field inspection of More than 1, but fewer than Treatment may or may not be pests and beneficials will eliminate unnecessary 4 weevils per trap per week justified. Do not treat unless insecticide applications during this period. The major field inspection at pinhead to concern during this period is ensuring adequate fruit 1/3-grown-square stage indi- set and preserving beneficial insect populations. cates presence of a damaging weevil infestation (see field in- Late-season is the remainder of the production spection method) or unless the season when the major concern is boll protection. number of weevils caught per Monitoring boll set may aid in making spray decisions trap for the week previous to pinhead square exceeds 10. in the late-season period. Boll protection is of primary More than 4 weevils per Treatment is probably concern as long as bolls which will be harvested are trap per week. justified. immature.

9 Bollworm and Tobacco Budworm of conventional insecticides are used to control bollworms and budworms, the percentage of budworms in Bollworm and tobacco budworm larvae are similar the infestation increases with each additional applica- in appearance and cause similar damage. Full-grown tion because of selection pressure. Aphid and other larvae are about 1 1/2 inches long and vary in color secondary pest infestations may increase following from pale green, pink or brownish to black, with bollworm/budworm sprays, especially when pyre- longitudinal stripes along the back. throids are used. Tobacco budworm and bollworm moths are at- Management and decision making. Cotton tracted to and lay eggs readily in cotton that is produc- fields should be scouted carefully every 3 to 5 days ing an abundance of new growth. Moths usually lay during periods of predicted moth egg-laying activity. single eggs on the tops of young, tender terminal In fields with fewer than five squares per row foot leaves in the upper third of the plant. Eggs are pearly (approximately 67,000 per acre), bollworm populations white to cream color and about half the size of a often collapse and cease to be a problem. pinhead. These should not be confused with looper eggs, which are flatter and usually laid singly on the Eggs and newly hatched worms are usually found in undersides of leaves. Eggs hatch in 3 to 4 days, the plant terminals and indicate possible outbreaks. turning light brown before hatching. Young worms Natural mortality agents such as weather and preda- usually feed for a day or two on tender leaves, leaf tors frequently control these pests before any damage buds and small squares in the plant terminal before occurs. Once worms have grown to larger than 1/2- moving down the plant to attack larger squares and inch long, natural and insecticidal control are less bolls. When small worms are in the upper third of the effective. Insecticides applied to control 1/2-inch long plant, they are most vulnerable to control by insecti- worms are only moderately effective. cides and beneficial insects and spiders. Frequently, examination of the upper third of the Sometimes moths deposit eggs on squares, bolls, plant (leaves, stems, squares, blooms and bolls) is all stems and, in general, lower parts of the plant. This that is needed to make a sound management decision. may occur when cotton plants are stressed and making However, when eggs are being laid all over the plants little new growth, or during periods of high tempera- or when 60 percent or more of the bolls are mature, ture and low humidity. Detection of eggs and control whole plant counts should be used. Mature, unopened of small worms are more difficult when eggs are bolls are firm, cannot be dented when pressed be- deposited in these locations. tween the thumb and forefinger, and cannot be cut easily with a sharp knife. Budworms are generally more resistant to insecticides than bollworms. Budworms are less numerous Before bloom. The decision to apply conventional than bollworms until mid-August or early September, insecticides (as opposed to microbial insecticides, ovici- and rarely reach damaging levels. Once certain kinds des or no treatment) for bollworm and budworm control during this period should be made very carefully. Conventional insecticides often kill beneficial insects and spiders, thus allowing a rapid increase in BOLLWORM/BUDWORM IDENTIFICATION bollworm numbers. Avoid making conventional Actual size of larvae insecticide treatments on the basis of egg numbers or of known age first signs of crop damage. Under most conditions, do not use conventional insecticides before blooms are observed in the field. Treatment may be warranted where 15 to 25 percent of the green squares examined are worm damaged and small worms are present. Consider using a microbial insecticide to preserve beneficial insects and spiders. Microbial insecticide use is discussed further on page 15. After bolls are present. Divide the cotton field into four or more manageable sections depending upon field size. Make whole plant inspections of five randomly chosen sets of three adjacent cotton plants in each section. Count the number of eggs, worms and key predators encountered and estimate the number of eggs, worms or key predators per acre using the following formula:

No. eggs, worms or key Worms, eggs predators counted or key predators = x no. of plants per acre No. of whole plants checked per acre

10 The number of plants per cotton acre is calculated from feeding punctures by the presence of a wartlike from counts of plants on at least 10 feet of row in four plug which the female places over the feeding site after locations in the field: she has deposited an egg in the cavity. The female deposits an average of 100 eggs during her life span of Row feet per acre about 30 days. Plants per acre = x Plants counted Row feet examined Eggs hatch into larvae, or grubs, within 3 to 5 days 522,720 Row feet per acre = under midsummer conditions. Grubs transform into Row spacing in inches pupae within the square or boll in approximately 7 to Treatment may be justified when counts aver- 11 days. Adults emerge 3 to 5 days later. The time age 5,000 or more small worms per acre. How- required for development from egg to adult under ever, if two or more key predators (see guidelines summer field conditions averages 17 days, with a for scouting for predators on p.6) are found for complete generation occurring in 21 to 25 days. each small worm, control measures may not be Punctured squares flare open and usually fall to the needed or a microbial insecticide may be used. ground within a week. Small bolls that are punctured The actual treatment level will vary according to the may also fall to the ground, but larger bolls remain on ability of the individual scout to locate small larvae, the plant. When direct sunlight and hot, dry condi- the age structure of the infestation, maturity of the tions cause fallen squares to dry out rapidly, large crop and crop value. numbers of weevil larvae do not survive. Bt transgenic cotton management. Research Boll weevil populations reach the highest level late trials evaluating the Bollgard® transgenic Bt gene in the growing season. As cotton plants mature and technology have determined it to be highly effective the number of squares is reduced, the percentage of against tobacco budworms. Bollgard® cottons are also boll weevil-damaged squares becomes an unrealistic effective against cotton bollworm, but under heavy indicator of damage because boll weevils are compet- pressure from this species insecticide treatment may ing for squares. As square numbers decrease, boll be needed. weevils may cause more damage to small bolls. The entire plant should be searched for tobacco Boll protection should be the primary concern as budworm and bollworm larvae and injury. A long as there is a significant number of immature bolls proper sample includes squares, white blooms, pink which can be expected to mature before the average blooms, bloom tags and bolls. Scouting intervals frost date or before the crop is terminated by a desic- should be reduced to 3 to 4 days during periods of cant or defoliant. Where economic weevil infestations increasing bollworm egg laying, especially during peak are encountered, protect bolls until the last bolls bloom. Treatment should not be triggered by the expected to be harvested are 12 to 15 days old. presence of eggs alone. Hatching larvae must first One or more insecticide applications made at feed on the cotton plant to receive a toxic dose. Treat- weekly intervals may be required to control moderate ment with foliar insecticides for tobacco bud- weevil infestations. For heavy infestations, it may be worm or bollworm should be considered when necessary to make several applications at 3- to 5-day 5,000 larvae per acre larger than 1/4 inch are intervals. present (based on a population of 40,000 to Management and decision making. When square 60,000 plants/acre) and 5 to 15 percent of the numbers are greater than the combined number of squares or bolls are worm damaged. blooms and bolls, inspect fields at least weekly, by As with non-Bt cotton, a range of treatment thresh- examining 100 squares that are at least 1/4 inch in size. olds is provided since many factors in addition to Sample the entire field since weevil infestations are density of larvae and square damage determine the often clumped. If 20 percent of the squares exam- need to treat Bt cotton with insecticides. Many of ined are weevil damaged, treatment should be these factors are the same as those listed above for considered. After peak bloom, or when bloom non-Bt cotton. As in non-Bt cotton, predators and and boll numbers exceed square counts, treat- parasites are very important in reducing the numbers ments should be initiated when 25 to 30 percent of eggs and larvae and they complement the control of the squares examined are weevil damaged. provided by these varieties. Once plants approach cutout and square densities The use of a non-Bt cotton refuge is a requirement decrease significantly, small boll damage should be for planting Bt cotton and is an important component used as the criteria for further insecticide applications. of resistance management. Boll protection is often warranted when 15 percent of the small bolls present are weevil damaged and at least two to four vulnerable, undamaged, Boll Weevil potentially harvestable bolls are counted per 10 Recently emerged adults feed on squares or bolls for row feet. Bolls that have sufficient time left to reach 4 to 8 days before mating and laying eggs. Adult maturity should be protected until they are at least 15 weevils puncture squares or bolls both for feeding and days old or until they can no longer be cut with a knife. egg laying. Egg laying punctures can be distinguished

11 Aphids Management and decision making. Pink bollworm pheromone traps should be placed in fields at Three species of aphids, or plant lice, seedling emergence and monitored at least weekly until feed on cotton plants: the cotton aphid, the 4- to 5-leaf stage, then daily until the 1/3-grown the cowpea aphid and the green peach square stage. If more than five moths are caught aphid. Cowpea aphids are shiny black per trap per night at the pinhead square stage, with white patches on the legs and can be common on insecticides or pheromone mating disruption seedling plants. Aphid infestations can occur from products or a combination should be applied. plant emergence to open bolls. Cotton aphids range in Subsequent treatments may be needed if indicated by color from light yellow to dark green to almost black. the trap catches. Terminate treatments prior to the 1/3- The immature or nymphal stage looks like the adult grown square stage. stage, only smaller. Most adults do not have wings. Aphids usually are found on the undersides of leaves, In areas where moths are captured in pheromone on stems, in terminals and sometimes on fruit. Heavy traps, field inspections for rosetted blooms should be and prolonged infestations can cause leaves to curl made after the crop is in the second week of bloom. downward, older leaves to turn yellow and shed, Since rosetted blooms caused by pink bollworms do not squares and small bolls to shed and bolls to be reduced result in economic damage, the rosetted bloom counts in size, resulting in incomplete fiber development. and pheromone trap data should be used for detection of infested fields and to time pheromone mating disrup- Honeydew excreted by aphids can drop on fibers of tion sprays for population suppression. Generally, open bolls. A black, sooty fungus sometimes develops insecticide applications should be reserved for later in on the honeydew deposits during wet periods. Fiber the season. from such bolls is stained, sticky and of lower quality, resulting in difficult harvest, ginning and yarn spin- Where rosetted blooms are detected in a field, inspec- ning. Natural control by unfavorable weather, preda- tions of 40 to 50 quarter-sized bolls should be made tors, parasites and pathogens can be effective in twice weekly. Collect bolls when walking diagonally holding populations below damaging levels. Some- across the field. Bolls should be cracked or cut and times aphid numbers increase to moderate or heavy examined for the presence of pink bollworms. Examine levels and then decline for no apparent reason. the inside of the carpel wall for the entrance wart or mines made by small larvae, and the lint and seed for Management and decision making. Although evidence of feeding or larvae. Pheromone traps can be high populations can develop prior to bloom, most helpful in identifying infested fields and timing insecti- economically damaging infestations generally develop cide applications, but should not be used without boll later in the season during the month of August. Fields inspections as a decision-making tool. Oil trap catches should be scouted twice per week since rapid in- of 60 to 100 moths per trap per night for three creases in aphid numbers can occur in a short time. A nights are a strong indicator that an adult flight is total of 60 leaves divided between the top, middle and underway and treatment may be needed. lower portion of the plant should be sampled from plants across the field to determine actual infestation When weekly boll counts indicate a 10 to 15 levels. Insecticidal control of cotton aphids should percent infestation during the first 6 weeks of boll be delayed until infestations exceed 50 aphids per set in upland cotton, or 5 to 10 percent in Pima leaf. Refer to the latest Cotton Aphid Task Force cotton, insecticide treatments are warranted. Apply Suggestions for further management information, insecticide treatments using pheromone trap catches as especially for insecticide resistant cotton aphids. a timing indicator or apply on a 5-day schedule. Where These are available at the county Extension office. infestations occur late in September, 40 to 50 percent of the top-crop bolls may be infested without economic loss in upland cotton. Pink Bollworm Termination of insecticide treatments. Terminate Pink bollworms are primarily late- insecticide treatments in upland cotton when the last season insect pests. Larvae will feed on squares in the bolls expected to be harvested are 30 days old. Bolls of early season without economic damage to the crop. this age are “rock hard” in firmness. Newly hatched But once bolls are present, they become the preferred pink bollworm larvae have difficulty entering the more food supply. Pink bollworm larvae prefer 15- to 20- mature bolls and surviving in the dry fibers. In Pima day-old upland cotton bolls. Pima cotton bolls remain cotton, treatments should be continued until 70 percent susceptible to damage until they are 35 to 40 days old. of the bolls are open. It is essential that bolls set during the first 4 weeks of Cultural control is the most desirable, satisfactory the boll-setting period be protected from pink boll- and economical method of controlling pink bollworms. worm damage. In Pima cotton it is important to Farming practices should be planned and conducted for protect the crop even longer, since it matures more early crop maturity and to permit crop termination by slowly. To provide this protection normally requires mid-September. The pink bollworm is seldom a prob- continued scouting and treatments if necessary until lem in the High and Rolling Plains areas. Cotton should mid-September for upland and the first of October on be harvested as early as possible. Stalks should be Pima. shredded and plowed (preferably with a moldboard) to

12 a depth of at least 6 inches. Plowing should be com- toward the bollworm threshold of 5,000 small pleted as early as possible. By law, they must be larvae per acre. When cotton matures and square plowed by February 1. feeding is of no consequence, thresholds should be raised to 20,000 small larvae per acre. Refer to "Management Guidelines for the Beet Armyworm in Beet Armyworm Cotton," available at the county Extension office, for Beet armyworm eggs are laid on both further management information. 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 Occasional Pests more solitary in their feeding habits. Early-season infestations feed on leaves and terminal areas. Occa- Grasshoppers sionally they destroy the terminal, causing extensive lateral branch development and delayed maturity. The lubber (Jumbo) grasshop- Early-season insecticide applications may be warranted per is a large, brown, clumsy when plants with undamaged terminals approach the grasshopper without fully lower optimal plant stand limits of two plants per row developed wings. It cannot fly but its hind legs are foot for dryland production and four plants per foot of greatly enlarged and it is a strong hopper. It can be row in irrigated production. Larvae skeletonize leaves extremely damaging to seedling cotton. Large numbers rather than chewing large holes in them. Damaging are capable of completely destroying stands, especially infestations sometimes develop late in the season when around field margins. beet armyworms also feed on terminals, squares, Management and decision making. Although blooms and bolls. Several factors can contribute to no economic threshold has been established for this these late-season beet armyworm outbreaks. These species, field observations have indicated that factors are: mild winters (e.g., absence of prolonged populations of one per 3 row feet in the field or freezing temperatures); late planting; delayed crop two per square yard in vegetation around the field maturity; heavy early-season organophosphate or pyre- may be capable of causing economic damage. throid insecticide use; prolonged hot, dry weather Other species. A number of other grasshopper conditions; presence of beet armyworms prior to species are occasional cotton pests. They generally bloom; and weather conditions that support long- move into fields from adjacent fence rows, ditch banks distance migration. Additional characteristics of high or field margins. risk fields that consistently appear to fit a pattern for Management and decision making. Damaging developing beet armyworm problems are: sandy and infestations need to be controlled early while grasshop- droughty soils; skip-row planting; fields with skippy, pers are small and still in crop border areas. Twenty open canopies; drought stressed plants; and fields or more grasshoppers per square yard in crop infested with pigweed. The likelihood of a heavy out- margins or 10 or more per 3 row feet in the field break increases as more of these factors occur in a are suggested treatment levels. given location. However, when beet armyworm populations are high all fields are susceptible. When beet armyworms begin to damage the fruit, control may Lygus Bugs be justified. Infestations usually are spotty within a The western tarnished plant bug (Lygus field, and careful scouting is necessary to determine the hesperus Knight) is one of several Lygus need for, and field area requiring, control. Beet army- species that feeds on cotton terminals, worms longer than 1/2 inch may be difficult to control. squares and small bolls. Adults are 1/4 inch Management and decision making. Scout the long, have a conspicuous triangle in the center of the field by using the Whole Plant Inspection Method back, are winged, and vary in color from pale green to described in the bollworm and tobacco budworm yellowish brown with reddish brown to black mark- section. Early Detection Threshold (Hatching Egg ings. Immature lygus bugs are called nymphs. They are Masses): from initiation of squaring to cutout, if uniformly pale green with red-tipped antennae; late two "active hits" (i.e., recently hatched egg masses instars have four conspicuous black spots on the thorax with actively feeding larvae) are detected per 100 and one large black spot near the base of the abdomen. row feet and conditions are optimal for a beet The nymph's wings are not developed, but nymphs can armyworm outbreak, treatment should be consid- move rapidly and are difficult to detect in cotton ered. Remedial Threshold (for advanced infesta- foliage. Small nymphs may be confused with aphids, tions during mid-season): when infestations are cotton fleahoppers and leaf hopper nymphs. Plant bugs mainly leaf feeding and small worm counts prefer legumes to cotton and usually are found in large exceed 20,000 per acre and at least 10 percent of numbers in areas of alfalfa or potato production or the plants examined are infested, control may be areas providing wild hosts such as clovers, vetches, warranted. If beet armyworm larvae have shifted mustard and dock. Lygus bugs are attracted to succu- from feeding on foliage to feeding on squares, lent growth; their feeding results in shedding of squares blooms and bolls, thresholds should be lowered and small bolls, stunted growth and boll deformation.

13 Feeding damage to small bolls is often characterized as Insecticide treatments generally are not recom- small black spots or small, sunken lesions. The feeding mended. that causes these spots or lesions may or may not penetrate the boll wall and damage developing seeds or lint. Damage to blooms appears as black anthers and Spider Mites puckered areas in petals. Spider mites infest the undersides of leaves, where Management and decision making. The need for they remove the sap from the plant and cause the lygus bug control is determined by their abundance in leaves to discolor. They may also infest bracts of relation to the fruiting condition of the cotton plants. squares and bolls, causing the bracts to desiccate and Fields should be inspected for lygus bugs at 4- to 5-day squares or small bolls to shed. Severe infestations can intervals using a drop cloth (see discussion on page 7). defoliate the cotton plant. Mite infestations most often During the first week of squaring, the economic occur in spots and in field margins. Increased spider threshold is one lygus bug adult or nymph per 3 mite populations usually follow multiple applications feet of row combined with less than 90 percent of insecticides for other pests, since insecticides square set. In the second week of squaring, the destroy natural spider mite predators. economic threshold is one lygus bug adult or Management and decision making. Treat when nymph per 3 feet of row combined with less than mites begin to cause noticeable leaf damage. Spot 85 percent square set. In the third week of squar- treatment of fields is encouraged when infesta- ing, the economic threshold is one lygus bug tions are restricted to small areas. adult or nymph per 3 feet of row combined with less than 75 percent square set. After the third week of squaring, the economic threshold is two Other Pests lygus bug adults or nymphs per 3 feet of row with Early season. Garden webworms, beet army- less than acceptable fruit retention. worms, yellowstriped armyworms, saltmarsh caterpil- After peak bloom, begin treatment when drop lars and cotton square borers are occasional pests of cloth counts exceed two lygus bug adults or cotton in this area. Cutworms can cause damage nymphs per 3 feet of row and plants have failed during the seedling stage. Keep fields as weed-free as to retain squares and set bolls normally during possible 3 weeks before planting to avoid cutworm the first 4 to 5 weeks of fruiting. problems. Garden webworms can be a problem on seedling to 6-leaf-stage cotton. High numbers of beet Research in Arizona and California indicates that armyworms, yellowstriped armyworms and saltmarsh the western tarnished plant bug (Lygus hesperus) may caterpillars can reduce plant stands. Treatment of be more difficult to control with insecticides and may isolated areas within a field or along field borders can require the use of higher labeled rates of suggested be effective in controlling these pests and reducing insecticides. their spread across the field. Late season. Fall armyworms, yellowstriped Stink bugs armyworms and saltmarsh caterpillars rarely cause Several species of stink bugs feed on economic damage when they feed only on leaves of squares and bolls. Feeding on bolls may cotton late in the season. Whiteflies can sometimes cause boll shed and/or seed damage and lint reach high numbers in September and October. staining. Stink bugs may move into cotton Management and decision making. Economic when grain sorghum in the area starts to mature. thresholds have not been established for these pests. Management and decision making. Examine 10 Control is a matter of judgment. Insecticides are row feet of cotton in several locations in the field. most effective if applied when worms are small. When there is an average of five or more stink bugs per 10 feet of row, feeding can cause exces- Systemic Insecticides at Planting sive loss of squares and small bolls and may stain lint. Stink bugs often are clumped near field margins. In areas where early-season thrips infestations Spot treatment provides effective control when this consistently damage young cotton each year, preventa- situation exists. tive systemic insecticide treatments have proved more effective than postemergence spray applications. In choosing either approach to early-season thrips con- Cabbage Looper trol, key factors to consider include the abundance of Cabbage looper eggs are laid singly, thrips on other host plants at cotton planting time, the mainly on the lower surfaces of leaves. Larval feeding variety planted, the acreage planted, the planting date, damage is characterized by leaf ragging or large holes available equipment and labor, drought tendencies, in the leaves. Looper larvae often are killed by a and the probability of having to replant. Limitations disease before economic foliage loss occurs. and advantages of both systemics used at planting and Management and decision making. No eco- postemergence spray applications should be evaluated nomic threshold has been established for this pest. carefully before making a choice.

14 Limitations of Systemics eggs alone is not recommended. Environmental factors such as hot, dry weather can significantly • The decision to invest in systemics must be made reduce field levels of eggs. Some other important before the severity of the thrips problem can be natural control factors include predacious insects and assessed; therefore, the net economic return is spiders and parasitic wasps. Natural egg control can uncertain. vary greatly between fields and times of the season. • If replanting is necessary, the initial systemic Often, high numbers of sterile eggs are found. If treatment is lost and a new treatment at addi- larval infestations exceed suggested treatment levels tional expense may be required. and large numbers of eggs are present, the addition of • Under unfavorable conditions for plant emer- an ovicide to the larvicide may be justified to enhance gence (such as poor seed quality, planting too overall control. deeply, seedling disease, Asochyta blight or cool, wet weather), some systemics may contribute to further stand reduction. Microbial Insecticides • In areas where producers typically plant late Microbial products which are natural pathogens of (such as the Uniform Optimal Planting Date in the bollworm and tobacco budworm are commercially the Rolling Plains) or where planting is delayed available as preparations of Bacillus thuringiensis (B.t.). until late May or early June, the likelihood of Field studies indicate that microbials are best suited having thrips problems is lessened significantly for square protection. They are slow acting and and the probability of economic returns from the should be used against infestations of worms during use of systemics is diminished considerably. the squaring period through the first 10 days of bloom- ing. They are not suggested for use after that point. • Heavy rains may leach systemics from the root zone, thus shortening the effective control period Microbials are effective against worm numbers up and necessitating a foliar spray for additional to 6,000 per acre. They do not destroy beneficial control. arthropods (predators and parasites), a characteristic which sets them apart from conventional insecticides. When beneficial arthropod populations are absent, Advantages of Systemics other insecticides provide more consistent control. • Systemics are effective when inclement weather Treat fields in which most larvae are not more than or field conditions prevent sprayer operation. 1/4-inch long. Infestations of larger worms should not • The activity of systemics within the plant is be treated with microbials. Maximum effectiveness relatively unaffected by rain and weathering with B.t. requires precise sampling of cotton plants during their normal period of effectiveness. during the fruiting period. Sampling should be conducted at least twice a week while squares are devel- • The use of systemics reduces pesticide drift to oping. Apply microbials with ground equipment at non-target sites and organisms and provides longer residual control than foliar sprays. the rate of 5 to 15 gallons of liquid per acre, or by air using 2 to 5 gallons per acre. • Under certain conditions, some systemics often stimulate more rapid early growth and sometimes increase yields which apparently cannot be attributed to early-season pest control alone. Registered Bacillus thuringiensis products and labeled rates for • Use of systemics at planting will prevent signifi- controlling bollworm and tobacco budworm. cant thrips damage when high thrips numbers Product Rate per acre (formulated material) infest plants as they emerge. • Protection from early-season thrips damage can Condor 0.5-1.67 qts. result in earlier maturity, which may be impor- Dipel DF 0.5-2.0 lbs. tant during years of deficient moisture, early crop Dipel ES 1.0-4.0 pts. termination, or pest buildups during late season. Javelin WG 0.25-1.5 lbs. • At this time there is no research-based economic threshold for thrips control using postemergence applications. Therefore, the current foliar application suggestions may be inappropriate. Diapausing Boll Weevil Control To pass the winter, weevils must be in a state of reduced activity known as diapause. To reduce the Ovicides spring population of boll weevils in cotton fields, These insecticides effectively reduce numbers of weevils should be suppressed before they leave the bollworm and tobacco budworm eggs. Because large field for hibernation sites. The more infested acreage numbers of eggs often fail to produce economically properly treated in an area, the less chance there is of damaging worm infestations, insecticidal control of damaging weevil numbers emerging early the next

15 season. To effectively reduce diapausing weevils in Suggested pesticides must be registered and labeled the fall, apply insecticides at 10-day intervals from the for use by the Environmental Protection Agency and period of October 1 to 15 until crop termination. the Texas Department of Agriculture. The status of Where regrowth occurs, additional insecticide applica- pesticide label clearances is subject to change and may tions may be warranted as long as weevils are present. have changed since this publication was printed. County Extension agents and appropriate specialists Protecting Bees from Insecticides are advised of changes as they occur. The USER is always responsible for the effects of Pollination is extremely important in producing pesticide residues on his livestock and crops, as well as many seed crops such as alfalfa, clover and vetch. problems that could arise from drift or movement of Honey bee pollination also is critical in the production the pesticide from his property to that of others. of cucurbits throughout the state, and supplements Always read and follow carefully the instructions on native pollinators. The role of honey bees and wild the container label. pollinators in contributing to increased yields and For additional information, contact your county fiber length of cotton is unclear. The importance of Extension staff or write the Extension Entomologist, insect pollinators in the production of hybrid cotton is Department of Entomology, Texas A&M University, well recognized, however. Where pollinating insects College Station, Texas 77843-2475, (979) 845-7026. are required for flower fertilization, the crop producer, insecticide applicator and beekeeper should cooperate closely to minimize bee losses: Endangered Species Regulations 1. Apply insecticides, if practical, before bees are The Endangered Species Act is designed to protect moved into fields or adjacent crops for pollina- and to assist in the recovery of animals and plants that tion. When bees are in the vicinity, evening are in danger of becoming extinct. In response to the applications after bees have left the field are less Endangered Species Act, many pesticide labels now hazardous than early morning applications. carry restrictions limiting the use of products or 2. Where insecticides are needed, consider their application methods in designated biologically sensi- toxicity. “Highly toxic” insecticides include tive areas. These restrictions are subject to change. materials that kill bees on contact during applica- Refer to the Environmental Hazards or Endangered tion or for several days following application. Species discussion sections of product labels and/or Insecticides categorized as “moderately toxic” or call your local county Extension agent or Fish and “relatively nontoxic” should be applied in late Wildlife Service personnel to determine what restric- evening or early morning when bees are not tions apply to your area. Regardless of the law, foraging. For information on hazards of insecti- pesticide users can be good neighbors by being aware cides to honey bees, refer to the table in E-6A, of how their actions may affect people and the natural “Suggested Insecticides for Managing Cotton environment. Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas.” Worker Protection Standard 3. To prevent heavy losses of bees, do not spray any insecticide directly on colonies and prevent The Worker Protection Standard (WPS) is a set of insecticide from drifting. Bees often cluster on federal regulations that applies to all pesticides used in the fronts of their hives on hot evenings. Pesti- agricultural plant production. If you employ any cide drift or direct spray at this time generally person to produce a plant or plant product for sale and results in high levels of mortality. 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 Policy Statement for Making three basic types of protection: you must inform Pest Management Suggestions employees about exposure, protect employees from exposure, and mitigate pesticide exposures that em- The information and suggestions included in this ployees might receive. The WPS requirements will publication reflect the opinions of Extension entomolo- appear in the “DIRECTIONS FOR USE” part of the gists based on field tests or use experience. Our pesticide label. For more detailed information, consult management suggestions are a product of research and EPA publication 735-B-93-001 (GPO #055-000-0442-1) are believed to be reliable. However, it is impossible The Worker Protection Standard for Agricultural Pesti- to eliminate all risks. Conditions or circumstances cides — How to Comply: What Employers Need to Know, which are unforeseen or unexpected may result in less or call Texas Department of Agriculture, Pesticide than satisfactory results even when these suggestions Worker Protection Program, (512) 463-7717. are used. Texas Cooperative Extension will not as- sume responsibility for such risks. Such responsibility shall be assumed by the user of this publication.

16 ADDITIONAL REFERENCES Number Title

B-933 Identification, Biology and Sampling of Cotton Insects E-5 Managing Cotton Insects in the Southern, Eastern and Blackland Areas of Texas-2003 E-5A Suggested Insecticides for Managing Cotton Insects in the Southern, Eastern and Blackland Areas of Texas-2003 E-6A Suggested Insecticides for Managing Cotton Insects in the High Plains, Rolling Plans and Trans Pecos Areas of Texas-2003 E-7 Managing Cotton Insects in the Lower Rio Grande Valley-2003 E-7A Suggested Insecticides for Managing Cotton Insects in the Lower Rio Grande Valley-2003 L-5142 The Proper Use of Cotton Harvest-Aid Chemicals B-1721 Cultural Control of the Boll Weevil: A Four Season Approach— Texas Rolling Plains B-6046 Guide to the Predators, Parasites and Pathogens Attacking Insect and Mite Pests of Cotton ($5.00) B-6107 Bt Cotton Technology in Texas: A Practical View B-6116 Texas Cotton Production — Emphasizing Integrated Pest Manage- ment ($15.00)

These publications can be obtained from the Texas Cooperative Extension Bookstore at: http://tcebookstore.org MP-1718 An Illustrated Guide to the Predaceous Insects of the Northern Texas Rolling Plains Available at: http://insects.tamu.edu/extension/ag_and_field.html

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 Texas Cooperative Extension is implied.

Cover photo by Winfield Sterling.

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