B-1220 5-07

Managing and Mite Pests of Texas CONTENTS

METHODS OF PREVENTING INSECT PEST INFESTATIONS ...... 3 Cultural management methods ...... 4 Biological management methods ...... 5

DIAGNOSING INSECT PEST INFESTATIONS ...... 6 Sampling ...... 6 Economic injury level ...... 6

CHEMICAL MANAGEMENT METHODS ...... 7 Seed insecticide treatments ...... 7 Soil insecticide treatments ...... 7 Foliar and grain head insecticide treatments ...... 8 Endangered Species Act ...... 8 Bees and other pollinators ...... 8 Inbred lines for hybrid seed production ...... 9

SEED AND ROOT INSECT PESTS ...... 9 Wireworms ...... 9 Red imported fi re ant ...... 10 White grubs ...... 10 Southern corn rootworm ...... 10

STEM AND LEAF INSECT PESTS ...... 11 Cutworms ...... 11 Yellow sugarcane ...... 12 Corn leaf aphid ...... 13 Greenbug ...... 14 Chinch bug ...... 16 Corn earworm and fall armyworm (whorlworms) ...... 17 Banks grass mite ...... 18

GRAIN HEAD INSECT PESTS ...... 19 Sorghum midge ...... 19 Corn earworm and fall armyworm (headworms) ...... 22 Sorghum webworm ...... 24 Grain head-feeding bugs ...... 25

STALK-BORING INSECT PESTS ...... 26 Sugarcane borer, southwestern corn borer, European corn borer, Mexican rice borer and neotropical borer ...... 26 Lesser cornstalk borer ...... 27 Sugarcane rootstock weevil ...... 27

POLICY STATEMENT FOR MAKING PEST MANAGEMENT SUGGESITONS ...... 28 WORKER PROTECTION STANDARD ...... 28 Managing Insect and Mite Pests of Texas Sorghum Greg Cronholm, Allen Knutson, Roy Parker and Bonnie Pendleton*

N INTEGRATED APPROACH TO years and dominate control practices. Ex- managing insect and mite pests can amples of key insect pests of sorghum are help Texas sorghum growers greenbug and sorghum midge. A and crop protection specialists: Some pests, such as Banks grass mite, ✦ prevent damaging insect pest infesta- are induced. These are present in sorghum tions; fi elds or surrounding areas, but usually in ✦ diagnose the presence and severity of an nondamaging numbers. They increase to eco- insect pest infestation; and nomically important levels after changes in cultural practices or crop varieties, or when ✦ control an infestation with insecticides insecticides are used for other insect pests. when preventive methods are not fully effective and sampling justifi es the need False chinch bug for insecticide. Leaffooted bug Wireworm Rice stink bug Sorghum has an advantage over other Southern green stink bug White grub Conchuela stink bug grain crops because it can withstand rela- Cutworm Spider mites tively harsh, hot, dry climates, but responds Southern corn rootworm Stalk borers Corn earworm Yellow sugarcane aphid well to favorable production conditions and Fall armyworm irrigation. The crop adds important agri- Greenbug Sorghum webworm Sorghum midge cultural diversity in a production region. Chinch bug Benefi cial associated with sorghum Corn leaf aphid Corn earworm often help reduce the severity of insect and Fall armyworm mites in sorghum and in other crops such as cotton. Sorghum is an important rotation crop with cotton and soybeans, and rotation helps manage some weeds, diseases and insect pests.

Some insect and mite pests can reach Stage of plant development damaging levels throughout the growing Seed Vegetative growth Flowering Grain maturity season. Others can cause damage only at (Seedling) (Whorl) (Boot) a specifi c plant growth stage. Figure 1 il- Figure 1. Sorghum insect pest occurrence. lustrates the probability of various insect and mite pests occurring at each plant development stage. Methods of preventing insect Most insect pests of sorghum are occa- pest infestations sional pests, meaning they cause economic Managing insect and mite pests of sor- damage in localized areas or only during ghum involves actions that prevent pests certain years. Usually only one or two key from increasing to high enough numbers insect pests are in any sorghum-growing to cause economic damage. These practices area in Texas. These insects occur most help avoid pests, reduce their abundance, slow their rate of increase, lengthen the * Extension agent-pest management; Extension ento- time it takes them to reach damaging levels, mologists; and associate professor of IPM-entomol- ogy; The Texas A&M University System. and/or increase the plant’s tolerance to the insect pest.

3 Cultural management methods abundance of southern corn rootworm, cut- Cultural management methods involve worms, sorghum webworm, sorghum midge using crop production practices to reduce and stalk-boring insects. Johnsongrass is a pest abundance or damage. non-cultivated host of many sorghum insect pests, including greenbug, yellow sugarcane Crop rotation involves successive use of aphid and sorghum midge. Destroying this host and non-host crops. Sorghum benefi ts weed is very helpful in managing insect most when rotated with a broad-leaf or pests. tap-rooted crop such as cotton or soybeans. Growing sorghum in a fi eld planted to a dif- Seed selection, seedbed preparation ferent crop the previous year signifi cantly and seed treatment are important in re- reduces the potential for problems from ducing the effects of sorghum insect pests. some insect pests, diseases and weeds. When deciding on a sorghum hybrid to plant, consider how well the hybrid is adapted to Crop rotation is especially effective the locale and its susceptibility to insect against insect pests with a limited host pests and diseases. range, long life cycle (one or fewer genera- tions a year) and limited ability to move Use sorghum hybrids that tolerate green- from one fi eld to another. For example, wire- bugs. Sorghum hybrids with loose (open) worms, white grubs and some cutworms rather than tight (compact) grain heads are have only one generation a year, must have less infested with larvae of corn earworm, a grass-type crop to develop and reproduce, fall armyworm and sorghum webworm, all and cannot move during the damaging lar- of which feed on developing kernels. Also, val stage from one fi eld to another. Thus, sorghum with open grain heads is less likely growing a crop such as cotton or soybeans to show the effects of grain deterioration in the fi eld before growing sorghum helps from weather, grain head-infesting bugs reduce the abundance of these soil-inhabit- and pathogens. Early, uniform hybrids ing pests. Sorghum growers should rotate avoid infestation by several insect pests, crops regularly. including sorghum midge, corn earworm and fall armyworm, in addition to avoiding Destroying the previous crop, volun- late-season weather problems. teer and alternate host plants eliminates breeding and/or overwintering habitats to Sorghum hybrids resistant to pathogens reduce insect pest abundance and damage. and with good standability also reduce the This involves mechanically or chemically detrimental effects of insect pests. Insect destroying sorghum plants soon after har- pests add to the stress on sorghum plants vest to kill or expose insect pests and remove during the growing season, and, combined their food supply. This method also includes with pathogen infection, increase plant destroying volunteer crop and alternate lodging. Some insect pests, such as green- host plants within and outside a fi eld. bug and corn leaf aphid, transmit and other sorghum Where conservation tillage practices are diseases. This problem is best dealt with by used, herbicides can be applied post-har- using disease-resistant sorghum. vest to kill crop, volunteer and alternate host plants. Herbicides stop crop growth Good seedbed preparation promotes rapid effectively and are compatible with cultural seed germination and seedling growth, management practices to reduce insect pest which are essential to avoiding damage by abundance. However, where conservation wireworms, red imported fi re ant and yellow tillage is practiced certain pests, especially sugarcane aphid. Rapidly growing seedlings stalk borers, may be more abundant. are more tolerant of damage. Destroying previous crop, volunteer and Fungicide- and insecticide-treated seed alternate host plants reduces insect pest protects against some diseases and seed- abundance the following year. This practice feeding insects. Seed pre-treated with is particularly important in reducing the the systemic insecticides imidacloprid (Gaucho®), thiamethoxam (Cruiser®), or

4 clothianidin (Poncho®) is protected against emies — predators, parasites and pathogens seed-feeding insects and those such as that kill insect pests. Natural enemies can and chinch bug that attack sorghum be used in three ways: during the seedling stage. However, this ✦ Conservation, or enhancing numbers of systemic insecticide also suppresses corn already existing natural enemies. Con- leaf aphids that attract benefi cial arthro- serving natural enemies is the most ap- pods needed for natural control of greenbug plicable biological management method and other insect pests. to suppress the abundance of sorghum Planting time should be as early as insect pests. practical, but not when temperatures are ✦ Augmentation, the mass culturing and too cool for rapid seed germination and seed- periodic release of a natural enemy. ling growth. In dryland areas of the state, ✦ Importation, the introduction of non-na- early planting usually takes advantage of tive natural enemies. seasonal rainfall patterns. Conservation of natural enemies involves Early planting avoids infestation and protecting existing natural enemies so they damage by some sorghum insect pests be- are abundant enough to suppress the insect cause plants grow beyond a vulnerable stage pests they attack. Sorghum hosts an abun- before these insect pests are present. Also, dance of natural enemies, primarily because young plants can reach a more tolerant stage of aphid infestations. The corn leaf aphid, before insect pests are present, be susceptible usually non-injurious to sorghum, often for a shorter period of time or mature before becomes very abundant. Corn leaf aphids an insect pest becomes abundant enough to attract many different natural enemies that cause serious damage. Early-planted sor- attack aphid and caterpillar pests. ghum generally avoids damaging numbers of sorghum midge, corn earworm, fall army- Natural enemies allowed to increase worm, sorghum webworm, stalk borers and can hold some insect and mite pests below grain head-infesting bugs. damaging levels. Insecticides often destroy natural enemies, because most insecticides Fertilizer and irrigation applied to used in sorghum are broad spectrum, killing sorghum can both help and harm efforts insect pests as well as natural enemies. The against insect pests. Using too much fertiliz- fact that insecticides kill natural enemies is er and irrigation can cause sorghum plants a primary reason for making sure insecti- to be succulent and attractive to sorghum cides are needed before applying them. Once insect pests and extend the time to matu- natural enemies have been destroyed, there rity. On the other hand, healthy, vigorously is no natural (biological) protection against growing plants better tolerate insect pest insect pests. This can cause a resurgence of infestation and other plant stresses. In ar- the treated pest or an increase of a second- eas with alkaline soils where iron-defi ciency ary pest such as corn earworm or spider is a problem, applying iron is important for mites. production of healthy sorghum. Sorghum pests most affected by natural Chinch bugs and spider mites favor hot, enemies are greenbug, corn earworm, fall dry conditions and stressed plants. Dense armyworm, sorghum webworm and spider stands of vigorously growing sorghum are mites. Important natural enemies include less susceptible to chinch bugs. Rainfall spiders, ladybird beetles, lacewing larvae, tends to reduce greenbug and spider mite syrphid fl y larvae, minute pirate bug, insidi- numbers. For most leaf-feeding insect pests, ous fl ower bug, damsel bug, big-eyed bug the potential to reduce yield depends par- and parasitic wasps. Predators affect abun- tially on plant condition. dance and rate of increase of greenbugs, of- Biological management methods ten preventing them from causing damage. This is particularly true when greenbug- Biological management methods reduce resistant hybrids are used. Parasites often insect pest abundance by using natural en-

5 terminate a greenbug infestation. Predators cal times when insect pests are likely to be are important in suppressing the abundance present, to determine the pests present, of corn earworms and fall armyworms that their abundance and damage. Growers may infest sorghum grain heads. Although sev- need to inspect fl owering sorghum daily eral parasites attack sorghum midge, their when assessing the abundance of sorghum effect is minimal. Several pathogens, mostly midge. Record the information collected dur- fungi, infect some aphids, chinch bug and ing each fi eld inspection for future reference caterpillars. to determine changes in insect abundance Augmentation is the purchase and peri- and plant damage. odic release of natural enemies not normally The number of samples needed depends occurring in suffi cient numbers to control on the size of the sorghum fi eld, uniformity, pests. Commercially available natural en- plant growth stage and severity of the insect emies sold for pest control in sorghum include infestation. Seldom are insect pests distrib- convergent lady beetles, lacewing fl ies and the uted evenly in a sorghum fi eld. Examine greenbug parasite . plants from all parts of a fi eld. Avoid exam- Naturally occurring convergent lady ining only fi eld borders. beetles help control greenbug infestations in Growers can estimate the abundance of sorghum. Convergent lady beetles also can be most insects in sorghum by visually inspect- purchased. These are collected from natural ing the plants and plant parts. Some insects, hibernating sites and stored in refrigerators. especially those infesting sorghum grain When released in the fi eld, they quickly fl y heads, are effectively sampled by using the away or feed at low and ineffective rates “beat-bucket” method. Insect pests that live without reproducing. in the soil are hard to detect and most need The effectiveness of augmenting other to be sampled before the crop is planted. natural enemies for control of sorghum pests Soil-dwelling insects, such as white grubs is unknown. Because defi nitive information and cutworms, can be found by searching on augmentation (when to apply, how many through the soil. Wireworms are diffi cult to to apply, etc.) is lacking, entomologists with detect in soil. A grain-baited trap can be used Texas Cooperative Extension cannot provide to attract them. (See wireworm section on guidelines for augmentation as a management page 9 for details.) tool in sorghum. For visual examination, randomly select Importation is the identifi cation, collection and carefully inspect plants to detect insects and release of natural enemies in areas where and associated damage. During inspection, they do not occur naturally. This method has consider other factors such as predators, been effective where an exotic pest has entered parasitized aphids, plant growth stage and Texas without the natural enemies that help condition. Visual examination is used most control the pest in its native country. Certain often to sample aphids, chinch bug, spider species of parasitic wasps and lady beetles that mites and sorghum midge. feed on the greenbug have been imported and The beat-bucket technique is the best way released in Texas. to estimate the number of corn earworm, fall armyworm, sorghum webworm and bugs in Diagnosing insect pest sorghum grain heads. Shake sorghum grain infestations heads vigorously into a 2.5- to 5-gallon plas- tic bucket. Then count the caterpillars and Sampling bugs in the bucket. Because adult bugs can Sampling insects and mites in sorghum fl y, take care to count those fl ying from the is critical to determining the severity of an bucket or sampled plant. infestation and the need for insecticide ap- plication. Insect pest numbers in sorghum Economic injury level fi elds can change rapidly. Inspect sorghum The economic injury level is the abun- at least once a week, especially during criti- dance of an insect pest or amount of plant

6 damage that justifi es applying insecticide. abundance, insect age and duration of at- Although economic injury levels provided tack, and stage and condition of the plants in this publication are based on research, attacked. consider them only guidelines, because en- Indiscriminate insecticide use can lead vironmental and crop conditions vary from to pest resistance, resurgence of the treated year to year and region to region. pest and outbreaks of secondary pests. Se- In some cases, an insecticide is applied lective insecticide use by application meth- when pest abundance is less than the eco- od, choice of product or dosage can greatly nomic injury level to prevent the pest from reduce the occurrence of these problems. causing economic loss and to allow time to Treating insect pests in sorghum can affect apply the treatment. This lower threshold the abundance of benefi cial and pest insects is called the economic threshold or action in adjacent crops. level. Economic injury levels for most insect Seed insecticide treatments pests are provided in tables that consider Seed treated with Gaucho® or Cruiser® differences in insecticide and application can be purchased to control wireworms, fi re costs and in the value (per 100 pounds) of ant, greenbug, yellow sugarcane aphid and the sorghum. To determine if the abundance chinch bug. Use of treated seed is discussed of insect pests justifi es applying insecticide, in the sections on these pests. Contact your fi rst estimate the expected market value per seed dealer to buy treated seed. 100 pounds at harvest. Then determine the Planting seed sometimes is treated with per-acre cost of control including the insec- insecticides such as malathion, chlorpyrifos ticide and application. Read down the fi rst or pirimiphos-methyl to control stored-grain column for the cost of control and across pests. These treatments do not control seed- the table columns for the market value of feeding insect pests once seed is planted. the crop. The abundance of the insect pest at that point in the table warrants the cost Soil insecticide treatments of control. Insecticides for controlling some soil-in- habiting insect pests must be applied before Chemical management methods the crop is planted or at planting time. Insecticides are chemicals that kill insects Granular or liquid formulations may be and other . They are powerful used. The formulation selected depends on tools and have several advantages. The available equipment and the target insect. major advantage is they are often the only Several application techniques are used to practical control for insect pests at or near treat soil: preplant row treatment, row band damaging levels. The key disadvantages of at planting and in-furrow at planting. insecticides are cost and broad toxicity. They Preplant row treatment requires special can harm nontarget organisms in the crop equipment to incorporate insecticide to and nearby areas. From a sorghum insect a depth of 2 to 4 inches. Row treatments management standpoint, cost of insecticide must be made after or during bed formation and killing natural enemies should be con- because further cultivation or bed shaping sidered when making control decisions. changes the position of insecticide in the Use an insecticide in the proper amount row. For best control, treat a band of soil 7 and only when necessary to prevent eco- to 10 inches wide and 2 to 4 inches deep, and nomic loss. The cost of achieving full crop place seed in the center of the band. potential can exceed potential benefi ts. Ap- Row band and in-furrow applications may ply insecticides only when insect pests are be used to apply insecticide to soil at plant- becoming more abundant and economic crop ing. The technique chosen depends on the loss is expected. When deciding whether to pest insect and how a particular insecticide apply an insecticide, consider the cost of is labeled. Mount the granular applicator insecticide applications, prevailing mar- spout or spray nozzle just behind the open- ket conditions, expected yield, insect pest ing plow or disc opener and in front of the

7 covering shovels or press wheel. Adjust Some insecticides discolor foliage of cer- spouts or nozzles to make the treatment tain sorghum hybrids. Yield losses may oc- band 6 to 8 inches wide, treating the seed cur from extensive leaf damage after these furrow as well as the covering soil. Incorpo- chemicals are used on susceptible hybrids. rating insecticide with the covering shovels Review the label carefully before using an is adequate. An insecticide also can be in- insecticide. If you do not know whether corporated with short parallel chains, loop the sorghum is susceptible to insecticide, chains, press wheels, fi nger tines or other consult the insecticide manufacturer and/or suitable devices. Do not apply insecticides seed company. Carefully follow instructions directly on seed unless the label clearly de- on the label of an insecticide container to scribes that use, because doing so usually avoid hazards to the applicator, wildlife and results in poor seed germination. In-furrow the environment. insecticide application for other insect pests does not adequately control white grubs Endangered Species Act when they are abundant. The Endangered Species Act is designed Some insecticides (e.g., aldicarb, car- to protect and to assist in the recovery of bofuran, phorate, terbufos) are systemic and plants that are in danger of and can be applied at planting. Applied to becoming extinct. In response to the Endan- soil, these chemicals are absorbed into the gered Species Act, many pesticide lebels now young growing sorghum plant and control carry restrictions limiting the use of products or suppress such early-season insect pests or application methods in designated biologi- as greenbug, corn leaf aphid, yellow sug- cally sensitive areas. These restrictions are arcane aphid and chinch bug. subject to change. Refer to the environmental Hazards or Endangered Species discussion Certain insecticides, besides being sections on product labels and/or call your systemic, are effective against some soil- county Extension agent or Fish and Wildlife inhabiting insect pests, such as wireworms Service personnel to determine what restric- and corn rootworms. The duration of sys- tions apply to your area. Regardless of the temic activity varies with insecticide and law, pesticide users can be good neighbors by rate, but insect pests are usually suppressed being aware of how their actions may affect for 2 to 6 weeks after application. people and the natural environment. Foliar and grain head Bees and other pollinators insecticide treatments Protect bees and other pollinators from Aircraft or ground machines may be used insecticides. Pollination by bees is impor- to apply insecticides to sorghum foliage and tant in producing such crops as alfalfa, grain heads. Aerial applications work best clover, vetch and cucurbits. Sorghum is an when insecticide swaths meet or overlap. important source of pollen for honey bees in Insecticide sprays are more effective and many parts of Texas. However, sorghum is hazards minimized when wind velocity is wind- or self-pollinated and does not require less than 10 miles per hour. insect pollinators. Nozzle size and number, ground speed Take care to minimize bee losses by: and pressure infl uence the rate of insec- ticide spray output per acre by a ground ✦ Applying insecticides, if practical, before machine. Calibrate the sprayer carefully to bees move into fi elds or adjacent crops. ensure the recommended amount of insecti- When bees are present in the fi eld or cide is applied. One nozzle per row usually vicinity, make applications during the is adequate for young sorghum planted in evening after bees have left the fi eld. rows. Two to three nozzles may be needed ✦ Using materials least toxic to bees and to adequately cover larger plants and broad- notifying beekeepers so they can protect cast-planted sorghum. Optimal pump pres- bees. sure depends on the kind of nozzle used.

8 ✦ Preventing insecticide spray from drifting adequate to promote rapid seed germina- directly onto bee colonies. tion; ✦ Cultivating to reduce noncrop plant mate- Inbred lines for rial; and hybrid seed production ✦ Planting sorghum in a fi eld where a tap- Inbred lines used for sorghum hybrid rooted crop such as cotton was grown the seed production are often more susceptible previous year. than hybrids to insect pest damage and Sample fi elds before planting to deter- insecticide phytotoxicity. The increased mine the need to use insecticide-treated susceptibility to insecticides and higher crop seed or to apply insecticide at planting. Soil value of sorghum for hybrid seed production examination and bait traps can be used to generally require lower economic injury lev- sample for the presence of wireworms. els for insect pests. Also, insect pests that infl uence seed quality and germination are To build a bait trap, place 6 to 12 ounces more important in hybrid seed production. of nontreated sorghum seed in a 4-inch-wide by 6- to 8-inch-deep hole. Cover the hole Monitor hybrid seed production fi elds with soil, and mark the trap with a stake. regularly and consider the increased suscep- Covering the trap location with a 4- by 4- tibility to insect pests and insecticide phy- foot sheet of black plastic warms the soil totoxicity. Before applying an insecticide, and makes trapping more effective. At least check the insecticide label carefully and 2 weeks before planting, install one trap consult the manufacturer and seed company for each 10 to 20 acres. Two weeks later, about possible phytotoxic effects. examine the grain in the trap and count Seed and root insect pests the wireworms. Also, growers may thor- oughly examine soil samples 1 foot square Wireworms by 4 inches deep. If you fi nd one wireworm Elateridae (wireworm) and larva per square foot or two or more larvae Tenebrionidae (false wireworm) per bait trap, treat either seed or soil with insecticide. Information on seed treatment proce- True and false wire- dures is in the section on seed treatment. worms are immature Seed treated with Gaucho® or Cruiser® also stages of click and dark- is labeled for wireworms. ling beetles, respectively. Wireworms generally are shiny, slender, cylindrical Table 1. Suggested insecticides for control of wireworms. and hard-bodied. Their Days from last application to: color ranges from yellow Insecticide Application rate Harvest Graze to brown. Wireworm Seed treatments Wireworms feed on Imidacloprid 8 fl oz/100 lbs seed See remarks planted sorghum seed, (Gaucho® 480) commercially applied preventing germination. Thiamethoxam 5.1 fl oz/100 lbs seed — — (Cruiser® 5FS) commercially applied To a lesser degree, they False wireworm At planting feed on seedling plant Terbufos See remarks roots, reducing plant stands and vigor. (Counter® 15G) 7 oz/1,000 ft of row 50 50 Cultural practices that reduce abundance Remarks of and damage by wireworms include: Imidacloprid. Do not graze or feed livestock on treated areas for 45 days ✦ Preparing good seedbeds and planting after planting. Terbufos. Do not place granules in direct contact with seed because seed when soil moisture and temperature are may be injured.

9 Red imported fi re ant Table 2. Suggested insecticides for suppressing white grubs. Solenopsis invicta Days from last application to: Insecticide Application rate Harvest Graze Under certain con- Commercially treated seed ditions in the eastern Clothianidin ® and southern parts of (Poncho 600) 5.1-6.4 fl oz/100 lbs seed — — the state, red imported At planting fi re ants feed on planted Terbufos See remarks (Counter® 15G) 7 oz/1,000 ft of row 100 50 seed. Worker ants chew Remarks through the thin seed Terbuos. Do not place granules in direct contact with seed because seed coat and remove the em- may be injured. bryo (germ). They rarely consume the endosperm cannot be controlled once sorghum is planted, (starch) of the seed. They their presence must be determined before prefer water-soaked or planting. Grubs damage sorghum by feeding germinating seeds, but Red imported fi re ant on the roots. They may kill small seedlings, also damage dry seeds. resulting in stand loss. Severely pruned Cultural management roots of larger plants result in plant stunting practices that reduce damage by wireworms and lodging and increased susceptibility to to planted sorghum seed also reduce damage drought and stalk rot organisms. by red imported fi re ant. Use seed with good Planting sorghum in a fi eld where a non- vigor and plant into a well-prepared seedbed grass crop was grown the previous year is the when soil temperature and moisture are most important cultural management tactic adequate for rapid seed germination. Firmly against white grubs. pack covering soil to prevent easy access of To determine the abundance of white grubs fi re ants to planted seed and thus reduce before planting, examine 1 square foot of soil damage by fire ants. Insecticide-treated in each 5 to 10 acres. If more than two white seed as described for wireworms is effective grubs are found per square foot, severe dam- against red imported fi re ants. Planting seed age to sorghum could result. No insecticides treated with Gaucho® or Cruiser® or in-fur- for white grubs are currently labeled for row, at-planting application of insecticide broadcast, incorporated application. If white may provide effective control. grubs average one per square foot, growers White grubs can adequately suppress them with a band Phyllophaga crinita and others application of terbufos. Southern corn rootworm White grubs are the Diabrotica undecimpunctata howardi larvae of May or June beetles. White grubs are characteristically “C- shaped” with white bodies and tan to brown heads and legs. Because the last abdominal segment is Southern corn root- transparent, dark-colored worm is the larval stage digested material can be of the spotted cucum- seen in the larva. Larvae ber beetle. Rootworms vary in size according to are small, brown-headed age and species. White grub and creamy white, with Rarely are white grubs wrinkled skin. They burrow into germinating serious pests of sorghum. However, because seeds, roots and crowns of sorghum plants. they can be present in a fi eld at planting and 10 Symptoms of rootworm damage include Granular or liquid formulations of several reduced stands, lower plant vigor, and the insecticides are labeled for in-furrow or row occurrence of “dead heart” in young plants. band application for controlling rootworm. Later in the season, maturity may be de- Base the need for insecticide treatment layed, weeds may increase in abundance on a fi eld history of previous damage by because of a nonuniform plant stand, and rootworms. Rotating insecticides decreases plants may lodge. Damage by southern corn the possibility of rootworms developing re- rootworms is most likely to occur in the area sistance. Seed treatment with Gaucho® or of Texas shaded on the map (Figure 2). Cruiser® helps control rootworms. Stem and leaf insect pests Cut wor ms Agrotis and Euxoa spp.

Cutworms of several species can damage sor- ghum. Cutworms are im- mature stages of moths that are active at night. Cutworm moths prefer to lay eggs in grassy and weedy fields. Eggs are Cutworm laid on stems or leaves of sorghum or grassy weeds or in the soil, and hatch in 2 to 14 days. The typical cutworm larva attacking sor- ghum is plump and curls into a “C” shape Figure 2. Areas of potentially economically damaging when disturbed. Larvae vary in color from southern corn rootworm infestations in Texas. grayish white to grayish black or brown de- pending on species. Fully grown larvae are 1 Table 3. Suggested insecticides for controlling southern corn root- to 2 inches long. Some species pass the winter worm. in the soil as pupae and others as adults; most Days from last overwinter as small larvae in cells in the soil, application to: Insecticide Application rate Harvest Graze under trash, or in clumps of grass. They start Commercially treated seed feeding in spring and continue growing until Clothianidin early summer, when they pupate in the soil. (Poncho® 600) 5.1-6.4 fl oz/100 lbs seed — — Larvae of most species remain underground At planting during the day and feed at night. Carbofuran See remarks The most common cutworms in sorghum ® (Furadan 4F) 24-32 oz/13,000 linear ft 75 75 (surface-feeding cutworms) cut plants off at, Chlorpyrifos See remarks (Lorsban® 15G) 8 oz/1,000 ft of row slightly below or above the surface of the soil. Terbufos See remarks Some (climbing or army cutworms) feed on (Counter® 15G) 4-7 oz/1,000 ft of row 100 50 above-ground plant parts; others are subter- Remarks ranean and feed on underground plant parts Carbofuran. Apply in seed furrow or 7-inch band and incorporate. including roots of seedlings. Chlorpyrifos. Apply once per season in a 6- to 7-inch band, behind the Cultural controls for cutworms include planter shoe and in front of the press wheel. plowing under or using herbicides to control Terbufos. Apply once per season in a 5- to 7-inch band directly behind the planter shoe in front of the press wheel, and not in direct contact with vegetation in late summer or early fall, de- seed. stroying weeds, and thoroughly preparing the NOTE: Lower rates of insecticides listed have been shown to provide most seedbed at least 4 to 6 weeks before planting. favorable economic returns; however, where severe infestations consis- Cutworms are more severe in weedy fi elds. tently occur, use the higher insecticide rate. 11 The presence of cutworms in sorghum cutworm control. Certain insecticides that is determined by visible damage to plants. control southern corn rootworms also help For surface-feeding and subterranean cut- control cutworms. worms, determine the number of severed or dead and dying plants per foot of row. Yellow sugarcane aphid Base your decision to apply insecticide on Sipha fl ava the degree to which an adequate stand is threatened. For cutworms that feed on Yellow sugarcane above-ground plant parts, signifi cant losses aphids usually are occur when more than 30 percent of the leaf lemon-yellow, but tissue has been eaten. under some condi- Insecticide sprayed as a broadcast treat- tions are pale green. ment on the ground and plants usually pro- They are covered with tects against cutworms. However, cutworms small spines and have spend the day hidden in the soil. Late-af- two double rows of ternoon applications sometimes are more dark spots on the effective. Insecticidal baits are effective back. Both winged Yellow sugarcane aphid against some cutworms, but are expensive. and wingless forms Insecticide applied at planting controls sub- live in the colony. This aphid feeds on many terranean cutworms. Apply the insecticide different grasses, including johnsongrass in a 6- to 7-inch band and incorporate it into and dallisgrass. Females give birth for 28 the top 1 to 2 inches of soil. days to living young, averaging two nymphs Aerial or ground application of approved a day by each female. Nymphs mature in 13 insecticide is effective in controlling cut- to 19 days; adults live for 25 to 30 days. worms in an established sorghum stand. Yellow sugarcane aphids feed on sorghum However, insecticide is more effective on and inject toxin into leaves of seedlings and climbing than on subterranean cutworms. older plants. Aphids feeding on seedling See Table 4 for insecticides suggested for plants turn the leaves purple and stunt growth. On more mature plants, leaves turn Table 4. Suggested insecticides for controlling cutworms. yellow. By the time discoloration symptoms Days from last are visible, plants have been injured sig- application to: nifi cantly. Damage often leads to delayed Insecticide Application rate Harvest Graze maturity and plant lodging that may be Chlorpyrifos See remarks (Lorsban® 4E) 16-32 oz/acre 30-60 30-60 worsened by associated stalk rots. (Lorsban® 15G) 8 oz/1,000 ft of row — — The presence of yellow sugarcane aphids (NuFos® 4E) 16-32 oz/acre — — (NuFos® 15G) 8 oz/1,000 ft of row — — must be determined soon after sorghum Cyfluthrin See remarks plants emerge. The presence of purple- (Baythroid® 2E) 1.0-1.3 oz/acre 14 colored seedling plants is an indication of a Cyhalothrin See remarks yellow sugarcane aphid infestation. Scout (Karate® 1E) 1.92-2.56 oz/acre sorghum by inspecting plants beginning (Warrior® 1E) 1.92-2.56 oz/acre the fi rst week of plant emergence and twice Zeta-cypermethrin (Mustang Max®) 1.28-4.0 oz/acre 14 45 weekly until plants have at least fi ve true Remark leaves. As plants grow larger, they become Chlorpyrifos. 4E - To minimize insecticidal injury, do not apply to drought- more tolerant of aphid feeding. Very small stressed plants or within 3 days after irrigation or rain except where seedling sorghum plants (one to three true insecticide is applied in irrigation water. The waiting period from last ap- leaves) often are signifi cantly damaged after plication to harvest or grazing is 30 days for the 16-oz rate and 60 days for the 32-oz rate. being infested for a week or less. Cyfl uthrin. If applied once or twice, green forage may be fed or grazed on Discoloration symptoms may be useful in the day of treatment. For three applications, allow at least 14 days between last application and grazing. assessing yield losses, and may be used in a Cyhalothrin. Do not graze livestock in treated area or harvest for fodder, decision to replant. Information in Table 5 silage or hay. describes plant damage and corresponding

12 percentage yield loss associated with levels Table 8. Economic injury levels for yellow sugarcane aphid based on percentage of seedling plants infested at the three true-leaf of damage. Do not consider the fi rst two stage. “seed leaves” when estimating damage. Control Economic injury levels presented in cost ($) Crop market value ($) per acre per acre 100 150 200 250 300 400 500 600 Tables 6 to 8 are based on the percentage of yellow sugarcane aphid-infested plants at Percent infested plants the 1, 2 or 3 true-leaf stage. Do not count 6 67 44 33 27 24 17 14 12 the two seed leaves that appear fi rst. 8 89 60 44 36 32 22 18 16 10 * 76 55 44 39 28 22 20 Many predators feed on yellow sugarcane 12 * 92 66 53 44 33 27 22 aphids, but the aphids are rarely parasit- *Do not treat. ized. Insecticides are currently the only way to manage yellow sugarcane aphids in sorghum. Seed treated with Gaucho® or Table 9. Suggested insecticides for yellow sugacane aphid. ® Days from last Cruiser or insecticide applied at planting application to: (carbofuran or phorate) reduces the sever- Insecticide Application rate Harvest Graze ity of yellow sugarcane aphid infestations Commercially treated seed (Table 9). Clothianidin (Poncho® 600) 5.1-6.4 fl oz/100 lbs seed — — Table 5. Estimated yield loss based on damage by yellow sugar- Imidacloprid cane aphids to three true-leaf stage sorghum plants. (Gaucho® 480) 8 oz/cwt — 45 Description % Loss/plant Thiamethoxam (Cruiser® 5FS) 5.1 oz/cwt — — No discoloration 0 Applied post-emergence Localized discoloration 8 Carbofuran See remarks Less than one entire leaf discolored 11 (Furadan® 4F) 8-16 oz/acre 75 75 One entire leaf discolored 31 Dimethoate See remarks More than one leaf discolored 54 (4E) 8-16 oz/acre 28 28 More than two leaves discolored 77 (5E) 6.4-12.8 oz/acre 28 28 Dying/dead plant 100 Remarks Carbofuran. Applicator must use proper protective equipment when ap- plying this highly toxic insecticide. Do not apply to foliage more than twice Table 6. Economic injury levels for yellow sugarcane aphid based per season. Do not apply after heads emerge from the boot. on percentage of seedling plants infested at the one true-leaf Dimethoate. Do not apply more than three times per season. Do not apply stage. after heads emerge from the boot. Control cost ($) Crop market value ($) per acre per acre 100 150 200 250 300 400 500 600 Percent infested plants Corn leaf aphid 6 15 10 8 6 5 4 3 3 8 20 13 10 8 7 5 4 4 10 25 17 12 10 9 6 5 5 Corn leaf aphids of- 12 30 21 14 12 10 7 6 5 ten infest the whorl and undersides of sorghum Table 7. Economic injury levels for yellow sugarcane aphid based leaves in great numbers. on percentage of seedling plants infested at the two true-leaf This dark bluish-green stage. aphid is oval-shaped, Control cost ($) Crop market value ($) per acre with black legs, cornicles per acre 100 150 200 250 300 400 500 600 and antennae. There are Percent infested plants winged and wingless 6 26 18 13 11 10 7 6 5 forms. 8 35 24 17 14 13 9 7 7 Corn leaf aphids are 10 43 29 22 17 16 11 9 8 found most frequently Corn leaf aphid 12 51 35 26 20 18 13 10 9 deep in the whorl of the middle leaf of pre- boot sorghum, but also occur on the under- sides of leaves, on stems or in grain heads.

13 When feeding, corn leaf aphids suck plant Greenbug juices but do not inject toxin as do greenbugs graminum and yellow sugarcane aphids. The most ap- parent feeding damage is yellow mottling of The greenbug is an leaves that unfold from the whorl. aphid that sucks plant This insect rarely causes economic loss juices and injects toxin to sorghum. In fact, they can be considered into sorghum plants. The helpful. Beneficial insects such as lady adult greenbug is light beetles are often attracted to feed on corn 1 green, approximately /16 leaf aphids. When corn leaf aphid numbers inch long, with a char- rapidly decline at sorghum heading, the acteristic darker green benefi cial insects are present to suppress stripe down the back. greenbug and other insect pests. These Usually, the tips of the benefi cial insects also are believed to move cornicles and leg seg- to adjacent crops, such as cotton, and help ments farthest from the manage insect pests in those crops. body are black. Winged When abundant, corn leaf aphids are eas- and wingless forms may ily seen within the whorl of sorghum plants. be present in the same The whorl leaf can be pulled from the plant colony. Greenbug and unrolled to detect aphids when numbers Females produce living of aphids are low. Occasionally, corn leaf young (nymphs) without mating. Under op- aphids will become so abundant on a few timum conditions, the life cycle is completed plants in a fi eld that grain head exertion in 7 days. Each female produces about 80 and development are hindered. Moisture- offspring during a 25-day period. stressed sorghum plants are more likely Greenbugs usually feed in colonies on the than non-stressed plants to be damaged by undersides of leaves and produce much hon- corn leaf aphids. Although very rare, infes- eydew. The greenbug may be a pest during tations on seedling sorghum might cause the seedling stage and in the boot or head- stand loss, and grain head infestations ing stage. Infestations may be detected by might cause harvesting problems. the appearance of reddish leaf spots caused Because corn leaf aphids prefer to live by the toxin greenbugs inject into the plant. and feed in the whorl of sorghum, aphid The reddened areas enlarge as the number numbers normally decline rapidly after the of greenbugs and injury increase. Damaged grain head exerts (emerges) from the boot. leaves begin to die, turning yellow then Sometimes molds grow on the honeydew brown. Damage at the seedling stage may that corn leaf aphids produce. Honeydew on result in stand loss. sorghum grain heads has been associated Larger sorghum plants tolerate more with harvesting problems. The aphid also greenbugs. Yield reductions during boot, transmits maize dwarf mosaic virus. flowering and grain-development stages Although insecticide is rarely justified, depend on greenbug numbers, length of time corn leaf aphids can be controlled with the greenbugs have infested the plants, and insecticides used for greenbugs. Seed treated general plant health. Many greenbugs on ® ® with Gaucho or Cruiser or the application booting and older plants can reduce yields of carbofuran, phorate or terbufos at planting and weaken plants that may later lodge. are effective in controlling corn leaf aphids. Scouting sorghum for greenbugs is easy. However, corn leaf aphids do not inject toxin Examine a minimum of 40 randomly selected as they feed and very rarely damage sorghum. plants per fi eld each week. Greenbugs are Because it is rarely a pest, sampling proce- seldom distributed evenly in a fi eld, so ex- dures and damage assessment information amine plants from all parts of the fi eld; avoid are unavailable. examining only fi eld borders. In fi elds larger than 80 acres, or if making a control decision

14 is diffi cult, examine more than 40 plants. leaves. Do not confuse greenbugs with the When deciding whether to control green- bluish-green corn leaf aphid, often found bugs, consider the amount of leaf damage, with greenbugs in the plant whorl. number of greenbugs per plant, percentage Greenbugs in a fi eld can increase 20-fold of parasitized greenbugs (mummies), num- per week, but the seasonal average is a 5- to bers of greenbug predators (lady beetles) 6-fold increase each week. Rain and preda- per plant, moisture conditions, plant size, tors suppress aphid abundance early in the stage of plant growth and overall condition season, although the increase of natural of the crop. It is important to know from enemies has a lag time of 1 to 2 weeks. A week to week whether greenbug numbers common parasitoid usually is responsible are increasing or decreasing. For example, for a rapid decline in aphid abundance late insecticide treatment would not be justifi ed if in the season. the recommended treatment level (based on Sorghum hybrids resistant to greenbug leaf damage) had been reached but greenbug are available commercially. However, green- numbers had declined substantially from bug biotypes have consistently occurred previous observations. and new resistant hybrids have had to be In seedling sorghum (less than 6 inches developed. Hybrids resistant to greenbug tall), greenbugs may be found on any part of biotypes C, E, I and K have been or are the plant including the whorl or in the soil at being developed. Using greenbug-resistant the base of the plant. When scouting seedling hybrids is suggested. Resistance mainly is sorghum, examine the entire plant and the tolerance, and therefore resistant hybrids soil around the base of the plant. Note the will not be free of greenbugs. Damage presence or absence of greenbugs and any thresholds for resistant are the damage to plants (yellowing, death of tissue). same as for susceptible sorghums because Refer to Table 10 for economic thresholds for thresholds are based on plant damage. greenbugs on different plant growth stages. When deciding on insecticide treatment, Plants can tolerate about 30 percent leaf consider the previously listed factors and loss before yield is reduced. Greenbug infes- consult the recommended treatment levels tations after sorghum fl owering and before in Table 10. When estimating leaf damage, the hard-dough stage should be controlled consider any leaf to be dead if more than before they kill more than two normal-sized 75 percent of its surface is red, yellow or leaves on 20 percent of the plants. In the brown. Do not mistake for greenbug damage Texas Blacklands, insecticide application is the natural senescence of the small bottom suggested when greenbugs are colonizing the leaves. Estimate an average leaf damage upper leaves of booting sorghum and causing level for the entire fi eld unless it is feasible red spotting or yellowing of leaves. to spot treat areas of the fi eld. These guidelines are based on the assump- The greenbug usually is susceptible to la- tion that greenbugs are increasing so rapidly beled insecticides (Table 11), but resistance that control by benefi cial insects is ineffec- to organophosphorous insecticides exists in tive. However, when more than 20 percent several counties in the Texas Panhandle. of the greenbugs appear brown and swollen from being parasitized, an insecticide treat- Table 10. Economic threshold levels for greenbug on sorghum at ment is usually unnecessary. Also, plants different plant growth stages. showing drought or other stress cannot Plant size When to treat tolerate as much greenbug damage without Emergence to 20% of plants visibly damaged (beginning to suffering reduction in yield. about 6 inches yellow), with greenbugs on plants Greenbug colonies usually begin on the Larger plant Greenbug colonies causing red spotting or to boot yellowing of leaves and before any entire leaves undersides of lower leaves and move up the on 20% of plants are killed plant. On most sorghum hybrids, only the un- Boot to heading At death of one functional leaf on 20% of plants dersides of lower leaves need to be examined, Heading to When greenbug numbers are sufficient to cause although in some cases greenbug colonies hard dough death of two normal-sized leaves on 20% of may be found fi rst on the undersides of upper plants 15 Continued extensive use of certain insecti- Chinch bug cides could expand the resistance problem. Blissus leucopterus leucopterus Where resistance exists in an area, apply the initial insecticide at the higher labeled Chinch bugs are spo- dosage rate and increased application vol- radic pests of sorghum in ume to ensure complete coverage. Texas. Adult chinch bugs are black, with reddish Table11. Suggested insecticides for controlling greenbug. yellow legs and with con- Days from last spicuous, fully developed application to: Insecticide Application rate Harvest Graze white forewings, each of Commercially treated seed which has a black trian- gular spot at the middle Clothianidin (Poncho® 600) 5.1-6.4 fl oz/100 lbs seed — — of the outer margin. Im- Imidacloprid mature chinch bugs re- Chinch bug (Gaucho® 480) 8 oz/cwt — 45 semble adults in shape Thiamethoxam but lack wings. Young nymphs are yellowish, ® (Cruiser 5FS) 5.1 oz/cwt — — later turning reddish with a white or pale Applied at planting yellow band across the front part of the ab- Aldicarb See remarks domen. Older nymphs are black and gray (Temik® 15G) 7 lb/acre 90 with a conspicuous white spot on the back Carbofuran See remarks (Furadan® 4F) 24-32 oz/13,000 linear ft 75 75 between the wing pads. Chlorpyrifos See remarks Eggs are laid behind the lower leaf (Lorsban® 15G 8 oz/1,000 ft of row sheaths of sorghum plants, on roots or in the Phorate See remarks ground near the host plant. The life cycle is (Thimet® 20G) 6 oz/1,000 ft of row 30 30 completed in 30 to 40 days, and there are at Terbufos See remarks (Counter® 15G) 7 oz/1,000 ft of row 100 50 least two generations a year. Chinch bugs Applied post-emergence overwinter as adults in bunch grass. They Carbofuran See remarks begin moving to sorghum when tempera- (Furadan® 4F) 24-32 oz/acre 75 75 tures reach 70 degrees F. Chlorpyrifos See remarks Adult and immature chinch bugs suck (Lorsban® 4E) 8-32 oz/acre 30-60 30-60 (NuFos® 4E) juices from stems, leaves or underground Dimethoate See remarks plant parts. Young plants are highly suscep- (4E) 8-16 oz/acre 28 28 tible. Older plants withstand attack better, (5E) 6.4-12.8 oz/acre 28 28 but they, too, become reddened, weakened Malathion See remarks and stunted. Chinch bugs are favored by hot, (57EC) 24 oz/acre 7 — dry weather, and large numbers of adult and Phorate See remarks (Thimet® 20G) 4.5-6.0 oz/1,000 ft of row 30 30 immature bugs often migrate from wild bunch Remarks grasses or small grains into sorghum. Aldicarb. Do not feed green forage to livestock. To fi nd chinch bugs, carefully examine Carbofuran. Applicator must use proper protective equipment when ap- plants and surrounding soil. Make at least plying this highly toxic insecticide. Do not apply to foliage more than twice fi ve random checks per fi eld. per season. Do not apply after heads emerge from the boot. Cultural practices that stimulate dense, Chlorpyrifos. Do not exceed three applications. The waiting period from last application to harvest or grazing is 30 days for the 16-oz rate and 60 vigorous plant stands are recommended days for higher rates. because these conditions are less favored by Dimethoate. Do not apply more than three times per season. Do not apply chinch bugs, and injury usually is reduced. after heads emerge from the boot. Plant sorghum as early as practical. Malathion. Do not graze or feed treated foliage. Apply insecticide when two or more chinch Phorate. Do not place in contact with seed. Do not feed foliage before grain harvest. bugs are found on 20 percent of seedling Terbufos. May be knifed in at bedding, or banded (except in West Texas) plants less than 6 inches tall. On taller plants, or knifed in at planting (see label for dosage differences). Do not place insecticide often is justifi ed when chinch bugs granules in direct contact with seed. For early-season control of light to infest 75 percent of the plants. Generally, moderate infestations.

16 one chinch bug per seedling sorghum plant Chinch bugs sometimes are diffi cult to con- reduces grain yield by 2 percent. trol with insecticides. In fi elds with a history of economically damaging infestations of chinch Table12. Suggested insecticides for controlling chinch bugs. bug, at-planting, soil-incorporated insecticides ® ® ® Days from last or Gaucho , Cruiser or Poncho treated seed application to: may be justifi ed. Granular insecticides must Insecticide Application rate Harvest Graze receive about one-half inch of rainfall after ap- Commercially treated seed plication to effectively suppress early-season Clothianidin chinch bug infestations. (Poncho® 600) 5.1-6.4 fl oz/100 lbs seed — — Imidacloprid If infestations reach the economic threshold (Gaucho® 480) 8 oz/cwt — 45 after plant emergence, apply post-emergence Thiamethoxam insecticide using at least 20 gallons of water (Cruiser® 5FS) 5.1 oz/cwt — — per acre through nozzles directed at the bases Applied at planting of plants. Control is seldom satisfactory on Aldicarb See remarks plants in the boot stage or later. Aerial insec- ® (Temik 15G) 7.5 oz/1,000 ft of row 90 ticide application is seldom effective and not Chlorpyrifos See remarks suggested. (Lorsban® 15G) 8 oz/1,000 ft of row 30 3 Terbufos See remarks (Counter® 15G) 7 oz/1,000 ft of row 100 50 Corn earworm and fall armyworm Applied post-emergence (whorlworms) Carbaryl See remarks Helicoverpa and Spodoptera frugiperda (Sevin®) (4F) 32-64 oz/acre 21 14 (80S or 80WSP) 1.25-2.5 lb/acre 21 14 Corn earworm and (4XLR+) 32-64 oz/acre 21 14 fall armyworm infest the Carbofuran See remarks whorls and grain heads of ® (Furadan 4F) 8-16 oz/acre 75 75 sorghum plants. Larvae Chlorpyrifos See remarks (Lorsban® 4E) 16-32 oz/acre 30-60 30-60 hatching from eggs laid (NuFos® 15G) on sorghum leaves before Cyfluthrin See remarks grain heads are available Corn earworm (Baythroid® 2E) 1.3-2.8 oz/acre 14 migrate to and feed on Cyhalothrin See remarks tender, folded leaves in (Karate® 1F) 3.84 oz/acre (Warrior® 1E) the whorl. Remarks To find larvae in sor- Aldicarb. Apply granules in furrow and cover with soil. Do not feed green ghum whorls, pull the Fall armyworm forage to livestock. whorl leaf from the plant Carbaryl. Use high-gallonage ground application directed at bases of and unfold it. Frass, or larval excrement, is plants. present where larvae feed within the whorl. Carbofuran. Ground application only. Use 20-30 gallons of water per acre. Do not apply more than twice per season. Do not apply after heads Damaged leaves unfolding from the whorl are emerge from the boot. ragged with “shot holes.” Although this may Chlorpyrifos. Apply with enough water to ensure a minimum spray volume look dramatic, leaf damage usually does not of 20-40 gallons per acre. Use ground equipment to direct spray toward reduce yields greatly, and control of larvae bases of plants. The waiting period from last application to harvest or grazing is 30 days for the 16-oz rate and 60 days for more than 16 oz. during the whorl stage is seldom economically Do not apply more than 48 oz per acre per season. Do not treat sweet justifi ed. Also, larvae within the whorl are sorghum. somewhat protected from insecticide. Cyfluthrin. If one or two applications are made, green forage may be fed or grazed on the day of treatment. If three applications are made, allow at Insecticide application may be justifi ed if least 14 days between last application and grazing. Direct applications at larval feeding reduces leaf area by more than the basal portion of the plant. 30 percent or is damaging the developing Cyhalothrin. Do not graze livestock in treated area or harvest for fodder, grain head or growing point within the whorl. silage or hay. See page 22 for information on these insects Terbufos. Apply in 5- to 7-inch band over the row in front of or behind press wheel and lightly incorporate into soil. Do not place granules in direct contact as pests of sorghum grain heads. with seed. For early-season control of light to moderate infestations.

17 Banks grass mite Hot, dry weather may favor a rapid in- Oligonychus pratensis crease in mites. Also, mites in sorghum may respond as induced (secondary) pests after an insecticide application for a key insect Large numbers of Banks pest such as greenbug. A rapid increase in grass mites sometimes spider mites after insecticide application occur on sorghum, espe- is thought to be caused by the tolerance of cially in more arid areas mites to some insecticides, the destruction of Texas. These mites of benefi cial insects, and the dispersal of are very small; females mites from colonies. are larger than males. After feeding, mites turn Natural enemies do not always control deep green, except for spider mites adequately. Because spider the mouthparts and fi rst mites increase more rapidly on moisture- two pairs of legs that stressed plants, irrigation, where available, remain light salmon col- should be timed to prevent plant stress. Banks grass mite ored. Eggs (about 50 per Also, spider mites may move from small female) are laid in webbing on the under- grains, especially , to sorghum. To sides of sorghum leaves. Eggs are pearly avoid this, plant sorghum away from small white, spherical, one-fourth the size of the grains. adults, and hatch in 3 to 4 days. The life Insecticides produce varying degrees of cycle requires about 11 days under favor- success. Historically, insecticidal control able conditions. of mites in sorghum has been erratic. In- Spider mites suck juices from the under- secticide application may be justifi ed when sides of sorghum leaves. Mite infestations 30 percent of the leaf area of most sorghum begin along the midrib of the lower leaves. plants in a fi eld show some damage symp- Infested areas become pale yellow initially toms from mite feeding. Thorough coverage and later become reddish on the top surface. is required; apply at least 3 to 5 gallons of The entire leaf may turn brown. As spider spray mixture per acre. Banks grass mites mites become more abundant on the lower are often resistant to insecticides. leaves, the infestation spreads upward through the plant. The undersides of heavily Table 13. Suggested miticides for controlling Banks grass mite. infested leaves have a dense deposit of fi ne Days from last webbing spun by the spider mites. Concentrate/ application to: Miticide unit area Harvest Graze Increases in spider mite abundance Dimethoate See remarks generally occur after sorghum grain heads (4E) 16 oz 28 28 emerge. Large numbers of spider mites oc- (5E) 12.8 oz 28 28 curring early in kernel development can Phorate See remarks (Thimet® 20G) 4.9 lb 30 reduce the ability of sorghum plants to Propargite See remarks make and fi ll grain. After kernels reach hard (Comite® 6.55E) 24-36 oz 60 30 dough, grain is not affected. However, if spi- Remarks der mites are very abundant sorghum plants Dimethoate Ground application: Apply in 25-40 gallons of water. Do not may lodge, resulting in harvest losses. apply more than three times per season. Do not apply after heads emerge from the boot. Do not use in the Trans-Pecos area. Inspect the undersides of lower leaves Phorate Broadcast into whorl of plant. Do not use in the Trans-Pecos area. carefully. Mites occur in colonies, fi rst along Do not feed foliage before harvest. midribs of leaves. Later they spread away Propargite. Do not apply more than once per season. Slight phytotoxicity from the midrib and up the plant to higher may occur on some sorghum hybrids. leaves. Webbing indicates the presence of mites. Mite infestations commonly begin along fi eld borders, and may spread quickly throughout a fi eld.

18 Grain head insect pests is available in the area. Numbers often drop late in the season. Sorghum midge A sorghum midge damages sorghum Stenodiplosis sorghicola when the larva feeds on a newly fertilized ovary, preventing normal kernel develop- The sorghum midge is ment. Grain loss can be extremely high. one of the most damag- Glumes of a sorghum midge-infested spike- ing insects to sorghum in let fi t tightly together because no kernel Texas, especially in the develops. Typically, a sorghum grain head southern half of the state. infested by sorghum midges has various The adult sorghum midge proportions of normal kernels scattered is a small, fragile-looking, among non-kernel-bearing spikelets, de- orange-red fl y with a yel- pending on the degree of damage. low head, brown anten- Effective control of sorghum midge re- nae and legs and gray, quires the integration of several practices membranous wings. that reduce sorghum midge abundance Sorghum midge During the sin- and their potential to cause crop damage. gle day of adult life, The most effective cultural management each female lays about 50 yellowish- method for avoiding damage is early, uni- white eggs in fl owering spikelets of sorghum. form planting of sorghum in an area so Eggs hatch in 2 to 3 days. Larvae are color- fl owering occurs before sorghum midges less at fi rst, but when fully grown, are dark reach damaging levels. Planting hybrids orange. Larvae complete development in 9 of uniform maturity early enough to avoid to 11 days and pupate between the spikelet late fl owering of grain heads is extremely glumes. Shortly before adult emergence, the important. This practice allows sorghum to pupa works its way toward the upper tip of complete fl owering before sorghum midges the spikelet. After the adult emerges, the increase to damaging levels. clear or white pupal skin remains at the tip Cultural practices that promote uniform of the spikelet. heading and fl owering in a fi eld are also A generation is completed in 14 to 16 days important in deciding on treatment and in under favorable conditions. Sorghum midge achieving acceptable levels of insecticidal numbers increase rapidly because of multiple control. To reduce sorghum midge abun- generations during a season and when sor- ghum fl owering times are extended by a range of planting dates or sorghum maturities. Sorghum midges overwinter as larvae in August 1 cocoons in spikelets of sorghum or johnson- grass. Johnsongrass spikelets containing June 30 diapausing larvae fall to the ground and become covered with litter. When sorghum June 20 is shredded, spikelets containing larvae fall June 10 to the ground and are disked into the soil. Sorghum midges emerging in spring do so June 5 before fl owering sorghum is available, and these adults infest johnsongrass. Sorghum midges developing in johnsongrass disperse May 26 to fi elds of sorghum when it fl owers. Early-season infestations in sorghum are May 10 usually below damaging levels. As the sea- son progresses, sorghum midge abundance Figure 3. Estimated latest sorghum fl owering dates most likely increases, especially when fl owering sorghum to escape signifi cant damage by sorghum midge.

19 dance, use cultivation and/or herbicides to found on sorghum grain heads along fi eld eliminate johnsongrass inside and outside edges, there should be little need to sample the fi eld. Where practical, disk and deep the entire fi eld. plow the previous year’s sorghum crop to However, if you fi nd more than one sor- destroy overwintering sorghum midges. ghum midge per fl owering grain head in Multiple insecticide applications are used border areas of a sorghum fi eld, inspect the to kill adults before they lay eggs. Sorghum rest of the fi eld. Sample at least 20 fl ower- planted and flowering late is especially ing grain heads for every 20 acres in a fi eld. vulnerable to sorghum midge. To determine For fi elds smaller than 20 acres, sample whether insecticides are needed, evaluate 40 fl owering grain heads. Flowering heads crop development, yield potential and sor- are those with yellow blooms. Avoid plants ghum midge abundance daily during sorghum within 150 feet of fi eld borders. Record the fl owering. Because sorghum midges lay eggs number of sorghum midges for each fl ower- in fl owering sorghum grain heads (yellow ing head sampled and then calculate the anthers exposed on individual spikelets), they average number of midges per fl owering can cause damage until the entire grain head head. Almost all of the sorghum midges seen or fi eld of sorghum has fl owered. The period on fl owering sorghum heads are female. of susceptibility to sorghum midge may last Next, calculate the number of fl owering from 7 to 9 days (individual grain head) to 2 heads (yellow blooms present) per acre. Re- to 3 weeks (individual fi eld), depending on cord the number of fl owering heads along a the uniformity of fl owering. length of row equal to 1/1000 of an acre. As To determine if adult sorghum midges are an example, for a row spacing of 40 inches, in a sorghum fi eld, check at mid-morning 13.1 row feet is equal to 1/1000 of an acre. when the temperature warms to approxi- Make counts in at least four areas of the mately 85 degrees F. Sorghum midge adults fi eld. If fl owering (plant maturity) is highly are most abundant then on fl owering sor- variable across the fi eld, additional sites ghum grain heads. Because adult sorghum should be sampled. Average all counts and midges live less than 1 day, each day a new multiply by 1000 to estimate the number of brood of adults emerges. Sampling must be fl owering heads per acre. If there is only one done almost daily during the time sorghum head per plant, then the number of fl ower- grain heads are fl owering. Sorghum midge ing heads per acre is equal to the percent adults can be seen crawling on or fl ying heads in bloom multiplied by the number of about fl owering sorghum grain heads. plants per acre. The simplest and most effi cient way to Sorghum midge density per acre is then detect and count sorghum midges is to calculated as the mean number of midges inspect carefully and at close range all per fl owering head x number of fl owering sides of randomly selected fl owering grain heads per acre. For example, if there are heads. Handle grain heads carefully dur- 30,000 fl owering heads per acre and scout- ing inspection to avoid disturbing adult ing records show an average of 0.5 sorghum sorghum midges. Other sampling methods midge per fl owering head, then there are can be used, such as placing a clear plastic an estimated 15,000 sorghum midges per bag or jar over the sorghum grain head to acre (0.5 sorghum midge per head x 30,000 trap adults. fl owering heads per acre). The percentage Because they are relatively weak fli- of fl owering heads changes rapidly during ers and rely on wind currents to aid their bloom and should be determined each time dispersal, adult sorghum midges usually the fi eld is sampled. are most abundant along edges of sorghum Studies have shown that the larvae from fi elds. For this reason, inspect plants along a single female sorghum midge will destroy fi eld borders fi rst, particularly those down- an average of 45 grain sorghum kernels. The wind of earlier fl owering sorghum or john- seed weight of sorghum hybrids averages songrass. If no or few sorghum midges are 15,000 seeds per pound (range of 12,000 to

20 18,000, depending on the hybrid). A loss of In this example, the fi eld density of 1.1 45 kernels per midge, therefore, represents sorghum midges is now above the economic 0.0030 pounds (1.364 grams) of grain. injury level of 0.9 per fl owering head and The economic injury level for sorghum treatment would be justifi ed. This shows midge can be calculated from the following the importance of considering the number equation: of flowering heads (grain susceptible to midge damage) in estimating the economic Number of injury level. sorghum (Cost of control as midges per $ per acre) x 33256 Economic injury levels, as determined = fl owering (Value of grain as $ per cwt) x from the above equation, are shown in Table head (Number of fl owering heads 14 for a range of typical treatment costs per acre, market values per 100 pounds of grain, In the equation above, the control cost is and numbers of fl owering heads per acre. the total cost of applying an insecticide for Use the equation for estimating injury lev- sorghum midge control and the grain value els for your actual control costs, crop value is the expected price at harvest as dollars and number of fl owering heads per acre. per 100 pounds. The value 33256 is a con- Insecticide residues should effectively sup- stant and results from solving the economic press sorghum midge egg laying 1 to 2 days injury equation. The number of fl owering after treatment. However, if adults still are heads per acre is determined as described present 3 to 5 days after the fi rst application above. of insecticide, immediately apply a second For example, assume fi eld scouting yields insecticide treatment. Several insecticide ap- an average of 1.1 sorghum midges per fl ow- plications at 3-day intervals may be justifi ed ering head and fi eld sampling shows the if yield potential is high and sorghum midges number of fl owering heads is 18,000 per exceed the economic injury level. acre. (This is equal to a plant population of 90,000 with 20 percent of the heads fl ower- Table 14. Estimated economic injury levels for sorghum ing and one head per plant.) If the value of midge for a range of factors. (This table is only a guide. Use the crop is estimated to be $4.00 per 100 the equation in the text to estimate the economic injury level pounds and the cost of control is $5.00 per in your field.) acre, the above equation yields the injury Economic injury level— level as: mean number of midges/flowering head $5.00 x 33256 2.3 sorghum midges = Control Crop Flowering Flowering Flowering $4.00 x 18,000 per fl owering head cost, value, heads = heads = heads= $/acre $100 lbs 18,000/acre 45,000/acre 67,500/acre In this example, the fi eld density of 1.1 5 6 1.6 0.6 0.4 sorghum midges per fl owering head is below 5 7 1.3 0.5 0.34 the injury level and treatment would not be 5 8 1.2 0.5 0.3 justifi ed. If the fi eld is scouted 2 days later 6 6 1.9 0.8 0.5 and the sorghum midge density is again 6 7 1.6 0.7 0.4 1.1 midges per fl owering head, but now the 6 8 1.4 0.6 0.35 number of fl owering heads has increased to 45,000 per acre (50 percent of the plants 7 6 2.2 0.85 0.6 now have a fl owering grain head in a plant 7 7 1.9 0.75 0.5 density of 90,000 per acre and one head per 7 8 1.6 0.65 0.45 plant), the injury level is now: $5.00 x 33256 0.9 sorghum midge per = $4.00 x 45,000 fl owering head

21 Table 15. Suggested insecticides for controlling sorghum the dark stripe appear doubled. Fully grown midge. 1 larvae are robust and 1 ⁄2 to 2 inches long. Days from last application to: Young fall armyworm larvae are greenish Insecticide Application rate Harvest Graze and have black heads. Mature larvae vary Chlorpyrifos from greenish to grayish brown and have (Lorsban® 4E) 8 oz 30 30 a light-colored, inverted, Y-shaped suture Cyfl uthrin See remarks on the front of the head and dorsal lines (Baythroid® 2E) 1.0-1.3 oz 14 lengthwise on the body. Cyhalothrin See remarks Corn earworm and fall armyworm larvae (Karate® 1E) 1.92-2.56 oz (Warrior® 1E) feed on developing grain. Small larvae feed on fl owering parts of the grain head at fi rst, Esfenvalerate (Asana® XL) 2.9-5.8 fl oz 21 — then hollow out kernels. Larger larvae con- Malathion sume more kernels and cause the most dam- (Fyanon® ULV) 8-12 oz 7 7 age. The last two larval stages cause about Methomyl 80 percent of the damage. Frass is common (Lannate®) in infested grain heads, on tops of upper (2.4LV) 12-24 oz 14 14 leaves and on the ground under plants. (90WSP) 4-8 oz 14 14 Natural mortality of small corn earworm Zeta-cypermethrin and fall armyworm larvae is normally very (Mustang Max®) 1.28-4.0 fl oz 14 45 high. Both corn earworm and fall army- Remarks worm moths can lay several hundred eggs Cyfl uthrin. If one or two applications are made, green forage may be fed or grazed on the day of treatment. If three applications are made, on sorghum grain heads before or during allow at least 14 days between last application and grazing. fl owering, but only a few larvae survive. Cyhalothrin. Do not graze livestock in treated area or harvest for Natural factors suppressing these insects fodder, silage or hay. include predators, parasites, pathogens and cannibalism among larvae. Corn earworm and fall armyworm Infestations occur less often in early- than (headworms) late-planted sorghum. An important man- Helicoverpa zea and Spodoptera agement tactic is to use sorghum hybrids frugiperda with loose (open) grain heads. Early-planted sorghum and hybrids with open grain heads usually are less infested. Corn earworm and fall Begin sampling for headworms soon after armyworm moths lay the fi eld fi nishes fl owering and continue at eggs on leaves or grain 5-day intervals until the hard dough stage. heads of sorghum. Newly To sample headworms, grasp the stalk just hatched corn earworm below the sorghum head, bend the head into larvae are pale in color 1 a clean, white, 5-gallon bucket, and vigor- and only ⁄16 inch long. ously beat the head against the side of the They grow rapidly and Corn earworm bucket. Headworms will fall into the bucket become variously colored, where they can be seen and counted. Sample ranging from pink, green at least 30 grain heads, selected at random or yellow to almost black. from across the fi eld. In fi elds larger than Many are conspicuously 40 acres, sample at least one grain head per striped. Down the side is Fall armyworm acre. Record the number of small (less than a pale stripe edged above 1 1 1 ⁄4 inch long), medium ( ⁄4 to ⁄2 inch long) and with a dark stripe. Down 1 large (longer than ⁄2 inch) headworms found the middle of the back is a dark stripe di- in the samples. Divide the total number of vided by a narrow white line that makes medium or large headworms by the number

22 of heads sampled to get the average number Two ways to determine the economic in- of headworms per head. Then multiply the jury level are presented. Both use the same average number of headworms per head by factors and yield the same results. The fi rst the number of heads per acre to calculate method uses the equations below to present the number of headworms per acre. (To esti- the threshold as the number of larvae per mate the number of plants or heads per acre head, while the second method shows the for various row spacings, see page 20.) results in table format as the number of Studies have shown that a corn earworm larvae per acre. The number of larvae per larva will consume about 0.010252 pounds acre can be divided by the number of heads (4.65 grams) of grain during its development per acre to yield the mean number of larvae in the sorghum head. However, estimating per head as an economic injury level. the economic injury level for headworms is Economic injury level for large larvae: complicated because the potential yield loss Cost of control varies with the size of the larvae. That is Number of large as $ per acre x 9754 = why it is necessary to record the number of larvae per head Grain value as $ per cwt x small, medium-size and large headworms. heads per acre 1 Small larvae (up to ⁄4 inch) consume very Economic injury level for medium-size little grain (about 10 percent of the total) larvae: and about 80 percent of them die in this Cost of control as Number of medium-size $ per acre x 9754 stage. Therefore, small larvae should not be = larvae per head Grain value as $ per cwt x considered in determining the economic in- heads per acre x 0.19 jury level. If most headworms are this size, sample the fi eld again in 3 to 4 days. If most Table 16. Economic injury level for large (longer than ½ inch) of the larvae are larger than ¼ inch at that corn earworm larvae shown as the number of larvae per acre. later time, determine which size (medium- When the number of larvae per acre exceeds the number in the size or large) is most common and use the table at a given cost of control and value of grain per cwt, the value of the protected grain exceeds the cost of control.1 corresponding equation below to calculate the economic injury level. Control cost Grain value $/100 lbs $/acre 6.00 7.00 8.00 10.00 If the infestation consists of about equal 6 9,750 8,500 7,250 5,750 numbers of medium-size and large head- 8 13,000 11,000 9,750 7,750 worms, use this equation: 10 16,250 14,000 12,250 9,750 Potential loss (no. of large larvae/acre x 12 19,500 16,750 14,750 11,750 (as lbs/acre) = 0.010252) + (no. of medium-size 1 This threshold table assumes all larvae will survive and com- larvae/acre x 0.19 x 0.010252) plete development.

Treatment would be economically justi- Table 17. Economic injury level for medium-size (¼ to ½ inch) fi ed if the value of the potential loss (loss in corn earworm larvae shown as the number of larvae per acre. pounds per acre x dollars per pound of grain) When the number of larvae per acre exceeds the number in the exceeded the treatment cost per acre. table at a given cost of control and value of grain per cwt, the 1 Most corn earworm larvae larger than ½ value of the protected grain exceeds the cost of control. inch will survive to complete development, Control cost Grain value $/100 lbs $/acre 6.00 7.00 8.00 10.00 and these large larvae are most damaging; 6 51,500 44,750 38,250 31,250 they consume 83 percent of the total grain 8 68,500 58,000 51,500 41,750 consumed during larval development. About 19 percent of medium-size larvae (¼ to ½ 10 87,750 73,750 64,500 51,500 inch long) survive beyond this stage. Thus, 12 102,750 88,250 77,750 62,000 1 the potential grain loss from medium-size This table assumes 81 % of the medium-size larvae will die in that stage and not contribute to additional yield loss. larvae is only 19 percent of the potential loss from large larvae.

23 Table 18. Suggested insecticides for controlling corn earworm sal stripes. When mature, larvae are about and fall armyworm in sorghum. 1 /2 inch long and covered with many spines Days from last and much hair. Pupae within a cocoon are Concentrate/ application to: Insecticide unit area Harvest Graze reddish brown, slender and sub-cylindrical. Carbaryl A generation requires 1 month; as many as (Sevin®) six generations may develop in a year. The (4F) 32-64 oz 21 14 larva overwinters in a cocoon on the host (80S or 80WSP) 1.25-1.8 lb 21 14 (4XLR+) 32-64 oz 21 14 plant. Cyfl uthrin See remarks Many sorghum webworms may be found ® (Baythroid 2E) 1.3-2.8 oz 14 in grain heads of late-planted sorghum. Cyhalothrin See remarks (Karate® 1E) 2.56-3.84 oz Young larvae feed on developing flower (Warrior® 1E) 2.56-3.84 oz parts. Older larvae gnaw circular holes in Esfenvalerate and feed on the starchy contents of matur- ® (Asana XL) 5.8-9.6 fl oz 21 — ing kernels, which usually are only partly Methomyl (Lannate®) consumed. Each larva may eat more than (2.4LV) 12-24 oz. 14 14 12 kernels in 24 hours. Larvae do not spin (90WSP) 4-8 oz. 14 14 webs (as the name might imply) over the Zeta-cypermethrin sorghum grain head but, when disturbed, (Mustang Max®) 1.75 to 4.0 fl oz 14 45 young larvae often suspend themselves by Remarks spinning a thin silken thread. Cyfl uthrin. If one or two applications are made, green forage may be fed or grazed on the day of treatment. If three applications are made, allow at Inspect for sorghum webworms when least 14 days between last application and grazing. grain heads begin to fl ower; continue at 5-day Cyhalothrin. Do not graze livestock in treated area or harvest for fodder, intervals until kernels are in the hard-dough silage or hay. stage. To examine grain heads for sorghum webworms, shake grain heads vigorously Sorghum webworm into a 2.5- to 5-gallon plastic bucket, where even small larvae can be seen and counted Nola sorghiella

Table 19. Suggested insecticides for controlling sorghum web- Sorghum webworms worm. occasionally infest grain Days from last Concentrate/ application to: heads of sorghum plant- Insecticide unit area Harvest Graze ed 2 to 3 weeks later Carbaryl than normal. This insect (Sevin®) occurs primarily in the (4F) 32-64 oz. 21 14 (80S or 80WSP) 1.25-2.5 lb 21 14 more humid eastern half (4XLR+) 32-64 oz 21 14 of Texas. Cyfl uthrin See remarks ® Adults are small, white (Baythroid 2E) 1.3-2.8 oz 14 Cyhalothrin See remarks moths active at night. (Karate® 1E) 2.56-3.84 oz They lay about 100 eggs (Warrior® 1E) 2.56-3.84 oz Sorghum webworm singly but fastened rath- Methomyl er securely to fl owering (Lannate®) (2.4LV) 24 oz 14 14 parts or kernels of sorghum. Eggs are round (90WSP) 8 oz 14 14 to broadly oval and are fl attened from top to Remarks bottom. Cyfl uthrin. If one or two applications are made, green forage may be fed Webworm larvae are somewhat fl attened, or grazed on the day of treatment. If three applications are made, allow at yellowish or greenish brown and marked least 14 days between last application and grazing. Cyhalothrin. Do not graze livestock in treated area or harvest for fodder, with four lengthwise reddish to black dor- silage or hay.

24 easily. Inspect at least 30 plants from a fi eld to ensure that sample estimates are reason- ably reliable. Sample at least one grain head per acre in fi elds larger than 40 acres. Insecticide application is economically justifi ed when grain heads are infested with an average of fi ve or more small larvae. Cul- Conchuela stink bug tural practices to reduce sorghum webworm The conchuela stink bug (Chlorochroa abundance include plowing sorghum resi- ligata) varies in color from dull olive or ash dues after harvest to destroy overwintering gray to green, purplish pink, or reddish pupae, planting as early as practical, and brown. The most characteristic markings using sorghum hybrids with loose (open) are orange-red bands along the lateral grain heads. margins of the thorax and wings and a spot Grain head-feeding bugs of the same color on the back at the base of the wings. Several species of true bugs, primarily stink bugs, may move in relatively large numbers from alternate host plants into sorghum during kernel development. Bugs infesting sorghum in Texas include rice stink bug, southern green stink bug, conchuela stink bug, brown stink bug (Eu- schistus servus), red-shouldered stink bug (Thyanta accerra), leaffooted bug and false chinch bug. Leaffooted bug The leaffooted bug (Leptoglossus phyllo- pus) is brown, oblong and just longer than 3 ⁄4 inch. A white band extends across the front wings. The lower part of each hind leg is dilated or leaf-like. Eggs are laid in rows of 15 to 35. Nymphs are reddish. Rice stink bug The rice stink bug (Oebalus pugnax) is 1 straw-colored, shield-shaped and ⁄2 inch long. Females lay about 10 to 47 short, cy- lindrical, light-green eggs in a cluster of two rows. Eggs hatch after 5 days, and nymphs False chinch bug require 15 to 28 days to become adults. The false chinch bug (Nysius raphanus) resembles the chinch bug but with more uniform color, ranging from gray to brown. 1 False chinch bugs are ⁄10 inch long. Large numbers of false chinch bugs occasionally migrate from wild hosts, such as wild mus- tard, to sorghum, but these insects usually concentrate in small areas of a fi eld. Southern green stink bug Bugs suck juices from developing sor- The southern green stink bug (Nezara 3 ghum kernels and, to a lesser extent, from viridula) is about ⁄4 inch long, green and other grain head parts, and may cause somewhat shield-shaped. Females deposit economic damage. The extent of damage 300 to 500 eggs in clusters of about 30. The depends on the number of bugs per grain eggs hatch in about 7 days, reaching the head, the duration of infestation, and the adult stage in about 6 weeks. 25 stage of kernel development when infes- Table 21. Suggested insecticides for controlling grainhead-feeding tation occurs. Bugs cause more damage bugs. Days from last early during kernel development and less Concentrate application to: as grain develops to the hard-dough stage. Insecticide per unit area Harvest Graze Both nymphs and adults can reduce grain Carbaryl See remarks weight, size and seed germination. Fungi (Sevin®) (4F) 32-64 oz 21 14 often infect damaged kernels, causing them (80S or 80WSP) 1.25-2.5 lb 21 14 to turn black and further deteriorate in (4XLR+) 32-64 oz 21 14 quality. Damaged kernels rarely develop Cyfl uthrin See remarks ® fully and may be lost during harvest. (Baythroid 2E) 1.3-2.8 oz 14 14 Cyhalothrin See remarks Grain head-feeding bugs tend to congre- (Karate® 1E) 2.56-3.84 oz gate on sorghum grain heads and sometimes (Warrior® 1E) 2.56-3.84 oz 30 — within areas of a fi eld. Use the beat-bucket Remarks technique to estimate abundance. Shake Carbaryl. Direct spray into heads for optimum control. sorghum grain heads vigorously into a 2.5- Cyfl uthrin. If one or two applications are made, green forage may be fed or grazed on the day of treatment. If three applications are made, allow at to 5-gallon bucket where bugs can be seen least 14 days between last application and grazing. and counted more easily. However, adult Cyhalothrin. Do not graze livestock in treated area or harvest for fodder, bugs will fl y from the sampled plant or the silage or hay. bucket. Count those that fl y from sorghum grain heads or from the bucket and those on plant leaves. Sample at least 30 plants Stalk-boring insect pests from a fi eld. Take at least one sample per acre in fi elds larger than 40 acres. Sugarcane borer Determine the average number of bugs Diatraea saccharalis per sorghum head. Then multiply the aver- Southwestern corn borer age number of bugs per head by the plant Diatraea grandiosella density per acre to calculate the number of bugs per acre. Use the table to determine European corn borer if the rice stink bug population exceeds the Ostrina nubilalis economic injury level. The action level for Mexican rice borer false chinch bug is 140 bugs per grain head Eoreuma loftini when infestation begins at the milk stage of Neotropical borer grain development. Diatraea lineolata Sugarcane borer Not all stink bug species in sorghum are economic pests. Several species, such as the These closely related in- spined soldier bug, prey on harmful insects sects tunnel in the stalks and thus are benefi cial. of sorghum, corn and Southwestern corn borer Table 20. Economic injury level for rice stink bug as number other crops. The biology of bugs per acre at the milk stage. of these four species can Control cost Grain value ($/cwt) be generalized: White to $/acre 6.00 7.00 8.00 10.00 buff-colored adult moths 6 30,500 27,000 23,000 18,500 lay clusters of elliptical to 8 40,500 35,000 30,500 24,500 oval, fl attened eggs that European corn borer 10 51,000 43,500 38,000 30,500 overlap like fish scales 12 62,000 52,500 46,000 36,500 in shingle-like arrange- ments on leaves of host plants. Eggs hatch in 3 to Mexican rice borer 7 days. The larval stage lasts about 25 days and the pu- pal stage about 10. There Neotropical borer are two to three genera- 26 tions a year. Larvae are creamy white, about Lesser cornstalk borer 1 inch long when fully grown, and most body Elasmopalpus lignosellus segments have conspicuous round brown or black spots. Spots are lighter colored or Larvae of the lesser absent on mature overwintering larvae. cornstalk borer attack Most stem-boring insects pass the winter as roots and bore into stalks fully grown larvae in cells inside stalks that of sorghum plants. Dam- remain after the crop is harvested. aging infestations of this Young larvae feed for a few days on leaves insect rarely occur in sor- or the leaf axis. Older larvae tunnel into the ghum. Larvae are light sorghum stalks. Larvae bore up and down bluish green with promi- Lesser cornstalk borer the pith of the stalk. Borer-infested stalks nent transverse reddish- may be reduced in diameter, and lodging of brown bands. They feed in silken tunnels infested plants can result. Boring by larvae covered with soil particles. Larvae pupate in the stem just below the grain head can in silken cocoons under crop debris. cause it to break and the grain head to fall. Lesser cornstalk borers usually are more Injury by borers makes the plant more sus- severe during dry periods and in sandy soils. ceptible to stalk rot diseases. Cultural practices that preserve moisture Planting sorghum early is important and increase organic matter in the soil because borers typically are more abun- discourage the insect. Early planting and dant in late-planted sorghum. Shredding rotation with nonhost crops help avoid stalks very close to the ground or plowing damage from lesser cornstalk borer. Insec- and disking stubble destroys overwintering ticidal control rarely is justifi ed, although larvae by exposing them to cold tempera- Warrior®, Karate®, Mustang Max® and Lors- tures in more northern regions of Texas. ban® are labeled products. This practice reduces borer abundance the next year. Sugarcane rootstock weevil To determine the presence of stem borers, Anacentrinus deplanatus examine the sorghum plants carefully. Small holes near the leaf axis indicate that a larva The sugarcane root- has entered the stalk. Once larvae have en- stock weevil infests sor- tered the stalk, stalks must be split to see ghum sporadically, espe- the larvae. Inspect leaves carefully, because cially during dry years eggs are hard to fi nd. Clusters containing 10 and in fi elds where john- to 20 individual eggs may be on the top or Sugarcane rootstalk songrass is abundant. weevil undersides of leaves, depending on the borer The adult weevil is species. Assess the abundance of eggs and 1 dark brown or black, about ⁄8 inch long and small larvae before larvae bore into stalks. 1 ⁄16 inch wide. The insect overwinters as an Insecticidal control is effective only if applied adult on ground protected by plant residues. before larvae bore into stalks. In early spring weevils infest wild grasses, such as johnsongrass, and later move to Table 22. Suggested insecticides for controlling Southwestern corn borer and European corn borer. sorghum. The female uses her mouthparts Days from last to make a small puncture at the base of the Concentrate/ application to: plant into which the egg is deposited and Insecticide unit area Harvest Graze concealed. About 16 eggs are laid and they Cyfl uthrin (Baythroid® 2E) 1.3-2.8 oz 14 14 hatch in 6 days. Larvae are white, legless 1 Cyhalothrin grubs about ⁄5 inch long when fully grown. A (Karate® 1E) 2.56-3.84 oz 30 — generation is completed in about 40 days. ® (Warrior 1E) 2.56-3.84 oz Adult weevils feed on young sorghum plants and crowns. This damage is notice- able but not as serious as that caused by

27 larvae. Larvae tunnel into the sorghum label clearances is subject to change and stalk just below or above the surface of the may have changed since this publication soil. Tunnels resemble those made by other was produced. County Extension agents borers, except they are much smaller and and appropriate specialists are advised of do not extend up the stalk. Larvae often are changes as they occur. found at nodes and near the outer surfaces The user is always responsible for the of the stalk. Their feeding often is respon- effects of pesticide residues on his livestock sible for a drought-stressed appearance and and crops, as well as for problems that could lodging of sorghum plants. Exit holes and arise from drift or movement of the pesticide feeding tunnels provide favorable areas from his property to that of others. Always where such pathogens as charcoal rot can read and follow carefully the instructions enter the plant. Economic thresholds for on the container label. this pest have not been established and usu- ally control has not been required, although Worker protection standard locally damaging populations may occur. The Worker Protection Standard (WPS) Policy statement for making is a set of federal regulations that applies to all pesticides used in agricultural plant pest management suggestions production. If you employ any person to The information and suggestions includ- produce a plant or plant product for sale ed in this publication refl ect the opinions and apply any type of pesticide to that crop, of Extension entomologists based on fi eld WPS applies to you. The regulations require tests, research and experience. However, it you to protect your employees from pesticide is impossible to eliminate all risk. Condi- exposure. tions or circumstances that are unforeseen You must inform employees about ex- or unexpected may result in less than satis- posure, protect them from exposure and factory results even when these suggestions mitigate pesticide exposures that they may are used. Texas Cooperative Extension will receive. WPS requirements will appear in not assume responsibility for risks. Such the “Directions for Use” part of the pesticide risks shall be assumed by the user of this label. For more detailed information, con- publication. sult Worker Protection Standard, 40 CFR Suggested pesticides must be registered part 170, or call the Texas Department of and labeled for use by the Environmental Agriculture, Pesticide Worker Protection Protection Agency and the Texas Depart- Program, (512) 463-7622. ment of Agriculture. The status of pesticide

28 Photographs were provided by Greg Cronholm, H.A. Turney, G. T. Bohmfalk, Charles Neeb, Robert Saldana, Bart Drees, Roy Parker, J.W. Stewart, Pat Morrison and Charles Cole.

3M, Revision