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Managing Insect and Mite Pests of Sorghum

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Managing Insect and Mite Pests of Sorghum B-1220 5-07 Managing Insect and Mite Pests of Texas Sorghum 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 aphid ................................................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 insects 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 maize dwarf mosaic virus 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
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