TABLE OF CONTENTS

• Seed Treatment
• Soil Treatment
• Wireworms, Fire Ants and Other Seed-Feeding Insects
• White Grub
• Southern Corn Rootworm
• Cutworm
• Lesser Cornstalk Borer

• Insecticide Application Methods and Precautions
• Hybrid Seed Production Fields
• Cutworms
• Greenbug
• Scouting Procedures for Greenbug
• Corn Leaf Aphid
• Yellow Sugarcane Aphid
• Chinch Bugs
• Banks Grass Mite
• Sorghum Midge
• Sorghum Webworm
• Fall Armyworm--Corn Earworm (Whorlworm and Headworm)
• Panicle-Feeding Bugs
• Sugarcane Borer--Southwestern Corn Borer

FIGURES

1. Areas of Economically Damaging Southern Corn Rootworm Infestations in Texas
2. Sorghum Flowering Dates
3. Sorghum Pest Occurrence Profile

Introduction

About three million acres of Texas farmland are utilized annually to produce sorghum. The potential economic value of sorghum, primarily as livestock and poultry feed, makes pest control an important factor in efficient and profitable production. Sorghum also is used extensively in rotation with cotton and soybeans and is important to weed and some disease control strategies.

Sorghum and other crops grown in a community share important insect relationships. Beneficial insects that reproduce in maturing sorghum often move to cotton and other crops and aid in the control of numerous pests. Therefore, control decisions carried out in sorghum may affect pests and beneficial insect numbers in neighboring crops.

Insect and mite pests of sorghum may reach damaging levels throughout the production season. Producers should be aware of the probable occurrence of various pests (Figure 3, page 16), be able to correctly identify pests, have knowledge of their economic injury levels, and be aware of the various methods that aid in their suppression. Proper choice and careful use of insecticides are important. Indiscriminate insecticide use can result in pest resistance, resurgence and secondary pest outbreak. Selective insecticide use by application method or dosage greatly reduces the occurrence of these problems.

Proper crop production planning and seedbed preparation, as well as periodic in-season field monitoring for the occurrence of pest problems, are important. Insect numbers do not always relate directly to plant damage. Factors such as plant vigor and stage of growth, moisture conditions, time of year, parasite and predator abundance and crop rotation are equally important.

Descriptions of pests and their damage, methods for making insect and mite counts and various pest control methods are included in this publication.

Policy Statement for Making Pest Management Suggestions

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

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

The USER is always responsible for the effects of pesticide residues on his livestock and crops, as well as problems that could arise from drift or movement of the pesticide from his property to that of others. Always read and follow carefully the instructions on the pesticide label.

Biological Control

Insect and mite infestations are often held below damaging levels by weather, inadequate food and natural enemies such as predators, parasites and pathogens. It is important to recognize the impact of these natural control factors and, where possible, to encourage their action.

Biological control is the use of living organisms (parasites, predators and pathogens) to control pests. Important natural enemies of insect and mite pests attacking sorghum include lacewings, convergent lady beetles, parasitic wasps, syrphid flies and minute pirate bug.

Biological control is most effective when used with other compatible pest control practices in an integrated pest management (IPM) program. These practices include cultural controls, host plant resistance and the selective use of insecticides when other practices fail to keep pest numbers below acceptable or economical levels.

Biological control agents present little or no risk to human health or the environment. Also few pests are known to have become resistant to natural enemies, as commonly occurs with insecticides. The Texas A&M University System is committed to the development of pest management tactics which use biological control.

Methods of biological control are conservation, importation and augmentation of natural enemies. Existing populations of natural enemies are conserved by avoiding the use of insecticides until they are needed to prevent the development of economically damaging pest infestations. As an example, corn leaf aphids rarely damage sorghum yet serve as an important food source for beneficial insects that can attack greenbugs and other pests. These naturally occurring populations of beneficial insects can be especially important when insecticide-resistant greenbugs are present. Insecticide impact can also be minimized by using insecticides that are more toxic to the target pest than to the natural enemy. Cultural practices can also encourage natural enemies.

Importation is the identification, collection and release of natural enemies into areas where they do not occur naturally. This method has been effective where an exotic pest has entered Texas without the natural enemies that help control the pest in its native country. Certain species of parasitic wasps and lady beetles that feed on the greenbug have been imported and released in Texas.

Augmentation is the purchase and periodic release of natural enemies that do not naturally occur in sufficient numbers to provide pest control. Commercially available natural enemies sold for pest control in sorghum include convergent lady beetles, lacewing flies and the greenbug parasite, Lysephlibus testaceipes.

Naturally occurring convergent lady beetles help control greenbug infestations in sorghum. However, convergent lady beetles commercially available are collected from natural hibernating sites and stored in refrigerators. When released in the field, they quickly fly away or feed at low and ineffective rates without reproducing. The effectiveness of augmenting other natural enemies for control of sorghum pests is unknown. Because definitive information on the application of augmentation (when to apply, what density should be applied, etc.) is lacking, entomologists with the Texas Agricultural Extension Service cannot provide guidelines for augmentation as a management tool in sorghum.

Soil Pests of Sorghum

True and false wireworms, white grubs, corn rootworms and cutworms are the most common soil pests of sorghum in Texas. Additionally, fire ants are common soil insect pests of planting seed in the eastern and southern areas of Texas. Non-crop plant materials are important food sources for soil pests. Cultivation practices and/or the use of herbicides that reduce crop residues and provide for weed-free fields are important in reducing soil pest densities. Proper seedbed preparation that provides for rapid seedling emergence and stand establishment and preplant soil inspection for the presence of soil insect pests are important. If damaging levels of soil pests are detected, approved insecticides may be applied to the seed prior to planting or to the soil using the broadcast, rowband or in-furrow method of application. Preplant seed treatment or planter box seed treatment has proven effective in controlling wireworms and corn rootworms where low densities were present. High densities of these pests require broadcast or band application of approved insecticides. Effective control of white grubs at densities greater than one per square foot is usually obtained only with the broadcast, incorporated application technique.

Seed Treatment

Seed treatment in the past was done by the seed company; however, because of restrictions on chemicals used on seeds, many commercial seed companies are not treating seeds. Direct seed treatment or planter box treatments have been used by growers where commercially treated seeds are not available.

Wireworms, fire ants and other seed-feeding insects may be effectively controlled by treating seeds with lindane. When treating seeds, the insecticide should coat each seed evenly. Use a concrete mixer, commercial or homemade seed treater to treat seeds. Sprinkle 1 pint of water on each 100 pounds of seed and mix this to coat the seed with moisture. Slowly add the correct amount of insecticide while mixing the seed, and mix thoroughly until the insecticide is evenly distributed on all seeds. Treated seeds should be planted within 20 days of treatment, since long exposure to the chemical may affect germination of some varieties. Do not use treated seed for human consumption or livestock feed.

Insecticides such as malathion, methoxychlor or pirimiphos - methyl are often applied to seed to control stored grain pests. These insecticides are not effective for control of soil pests.

Certain precautions should be followed when lindane is used on planting seed since it can slow germination under cold, wet soil conditions. Do not use more than the labeled rate; in fact, when soil temperatures are unusually cool or hot, reduce the rate according to label instructions. Make sure to redistribute planter box applied materials once or twice per day or when adding seed. If the 7-day forecast is for a cold, wet period or the soil temperature is marginal for seed germination, it may be best not to use lindane. Do not apply lindane to sorghum seed already treated with heptachlor. Despite all these precautions, lindane seed treatment has been an effective, low-cost method of protecting planting seed from insect attack.

Soil Treatment

Insecticide for controlling some soil pests must be applied before the crop is planted or at planting time. Granular or liquid formulations may be used. The formulation used usually depends on the producer's equipment and the target insect. Granular forms of insecticide are generally safer and more convenient. With the soil method there are three application techniques: (1) preplant broadcast, (2) row band, and (3) in-furrow at planting.

Preplant Insecticide Application. A broadcast application generally provides the best protection against soil insects and is the only means of controlling heavy infestation levels of white grubs. Unfortunately, broadcast applications require more insecticide and are more expensive than row band or in-furrow treatments and, therefore, are usually not recommended. However, when broadcast applications are necessary, the insecticide should be applied uniformly to the field and incorporated to a depth of 2 to 4 inches immediately after application.

When sorghum is planted on a bed, special equipment is required to incorporate the insecticide to a depth of 2 to 4 inches. This is called row treatment. Row treatments must be made after or during bed formation, since further cultivation or bed shaping will alter the position of the insecticide in the row. A treated band of soil 7 to 10 inches wide and 2 to 4 inches deep, with seed placed in the center of the treated band, is necessary to obtain the best control.

Insecticide Application at Planting. Insecticides may be applied to the soil at planting time by the row band or in-furrow techniques. The technique of choice will depend on the pest insect and how a particular insecticide is labeled.

Mount granular application equipment on the planter with the spout just behind the opening plow or disc opener and in front of the covering shovels or press wheel. Adjust the spouts so that the treatment band is about 6 to 8 inches wide and so that the seed furrow, as well as covering soil, is treated. Incorporation of the insecticide by use of covering shovels is adequate. Insecticide can also be incorporated with short parallel chains, loop chains, press wheels, finger tines or other suitable devices. Some insecticides are labeled only for band application behind the seed covering devices. Do not apply insecticides directly on the seed unless the label clearly describes that use, since doing so usually results in poor seed germination. Where white grubs are abundant, in-furrow application usually produces poor control.

Some insecticides (e.g., aldicarb, carbofuran, disulfoton, phorate, terbufos, etc.) have systemic activity and can be applied at planting. When these chemicals are applied to the soil, they are absorbed into the young growing sorghum plant and will suppress some early season insect pest species such as greenbug, corn leaf aphid, yellow sugarcane aphid and chinch bug on seedling plants. Certain chemicals, besides being systemic, are effective against some species of soil inhabiting insect pests such as wireworms and corn rootworms. The duration of systemic activity varies with the insecticide and rate, but generally insect pest suppression is provided for two to three weeks after application.

For specific pesticide control suggestions, limitations and rates of each insecticide labeled for use on sorghum, refer to the insecticide suggestion tables for each insect pest.

Wireworms, Fire Ants and Other Seed-Feeding Insects

True and false wireworms are immature stages of click and darkling beetles. Wireworms are generally shiny, slender, cylindrical and hard-bodied. They range in color from yellow to brown.

Wireworms damage sorghum by destroying planted seed or, to a lesser degree, by feeding on seedling plant roots. Plant stands and vigor are reduced. Sampling of fields for the presence of wireworms prior to planting is recommended. Soil samples 1 foot square by 4 inches deep should be examined thoroughly. If two or more wireworm larvae per square foot are detected, control measures should be implemented.

Cultural practices that reduce non-crop plant materials in fields or rotation to tap-rooted crops that are unfavorable for wireworm development are important non-chemical control methods.

Lindane applied as a seed treatment or planter box treatment, is effective in controlling wireworms and fire ants. Pretreated commercial seed may sometimes be purchased for wireworm control. Check the label to see if such seed has been treated for soil insects. See seed treatment procedures for specific treatment procedures.

Under certain conditions fire ants will feed on planting seed. In addition to treated seed, use seed with good vigor and plant into a well prepared seed bed. Firm up the covering soil to reduce chances of fire ant damage.

White Grub

White grubs are the larval stages of May or June beetles. Larvae are characteristically "C-shaped" with a white body and a tan to brown head. Larvae vary in size according to age and species. The last abdominal segment is transparent, and dark colored digested material can be seen in the larvae.

Damage to plants results from larvae feeding on the roots. Small seedlings often are killed, resulting in stand loss. Severely pruned roots of larger plants result in stunting, plant lodging and increased susceptibility to drought and stalk rot organisms.

The need for white grub control, using a soil insecticide, can be determined by soil sampling. Examine a 1-square-foot soil sample for each 5 to 10 acres before planting. If white grub numbers exceed two per square foot, broadcast insecticide. On the same day as treatment, incorporate the insecticide into the top 2 to 4 inches of soil using a disc, field cultivator or equivalent equipment. If white grubs average approximately one per square foot, adequate suppression can be achieved in most instances with an in-furrow or band treatment at planting.

Southern Corn Rootworm

Southern corn rootworm is the larval stage of the spotted cucumber beetle. Rootworms are small, brown headed, creamy white larvae that burrow into the germinating seeds, roots and crowns of sorghum plants. Reduced stands and plant vigor, and the occurrence of "dead heart" in young plants, are characteristic of rootworm damage. Delayed maturity, increased weed abundance and plant lodging may occur later in the season in corn rootworm damaged stands.

Granular or liquid formulations are labeled for in-furrow or preplant use for control of corn rootworm. These insecticides are recommended for corn rootworm control in the area of Texas shaded on the map (Fig. 1). Base treatments on field history of previous damage. It is recommended that chemicals be rotated to decrease the possibility of rootworms developing resistance. Seed treatment with lindane is effective in controlling low infestation levels of corn rootworms present at planting time.

Fig. 1. Areas of economically damaging southern corn rootworm infestations in Texas.

Cutworms

Several cutworm species can damage sorghum. Cutworms are the immature stages of moths that are active at night. Grassy sod and weedy fields are attractive to moths for egg laying. Some subterranean cutworms feed on the seedling root system. These cutworms often overwinter in the field.

Subterranean cutworms can be suppressed with soil insecticide applied at planting. Incorporation of insecticide into the top 1 to 2 inches of soil in a 6- to 7-inch band is best. Refer to labels of insecticides listed for southern corn rootworm on page 5 for their cutworm status.

Cultivation practices and/or the use of herbicides that reduce non-crop plants in planted and in fallowed-fields are important cutworm control methods.

Aerial or ground application of approved insecticides is effective in controlling cutworms in established sorghum stands. These applications are more effective on the climbing cutworm species than on the subterranean species.

Lesser Cornstalk Borer

Larvae of the lesser cornstalk borer attack the root system and lower stalk of sorghum plants. Larvae are light bluish-green with prominent transverse brown bands. They feed in silken tunnels covered with soil particles. After completion of feeding, larvae pupate in silken cocoons under crop debris.

Cultural practices which increase moisture and crop residue, along with early planting and rotation to non-host crops, will reduce damage from lesser cornstalk borer.

Aboveground Pests of Sorghum

Sorghum is susceptible to aboveground insect pests throughout its growth and development. Some insects attack sorghum over a broad range of developmental stages while others only attack the plant at a specific stage of growth (Figure 3).

Regular monitoring of pests in the field is important for making good management decisions. Field inspections should be made at least weekly throughout the growing season, although a specific insect pest(s) may require more frequent monitoring.

Insecticide Application Methods and Precautions

Ground machines or aircraft may be used to apply most insecticides to sorghum. For best results with aerial applications, swaths should meet or overlap.

Spray applications are most effective and hazards minimized when wind velocity is less than 15 miles per hour. Avoid spraying when plants are wet. For broadcast crops, number 3 cone nozzles set 20 inches apart on a rearmounted boom of a tractor sprayer are satisfactory. A pump pressure of 60 pounds per square inch is recommended.

Nozzle size and number, ground speed and pressure influence the rate of output per acre; therefore, calibrate the sprayer carefully to ensure application of recommended insecticide amounts. One nozzle per row usually is adequate for young row crops, but two to three nozzles per row may be desirable on larger plants to obtain adequate coverage.

A number of insecticides discolor the foliage of certain sorghum hybrids. Yield losses have resulted from extensive leaf damage following the use of these chemicals on susceptible sorghum hybrids. Before application, check the insecticide label closely and consult the manufacturer and the seed company regarding possible phytotoxic effects. Insecticides which are known to cause extensive phytotoxicity are not recommended in this publication. Always follow label instructions carefully to avoid hazards to the applicator, wildlife and the environment.

Hybrid Seed Production Fields

Inbred lines used in sorghum hybrid seed production often are more susceptible to insect pest damage and insecticide phytotoxicity than hybrids. The increased susceptibility to chemicals and higher crop value generally demands lower economic threshold levels for insect pests. Also, insect pests that influence seed quality and germination have increased in importance in hybrid seed production. Hybrid seed production fields should be monitored regularly and consideration given to the increased susceptibility to insect damage and insecticide phytotoxicity. Before insecticide application, check the insecticide label closely and consult the manufacturer and the seed company regarding possible phytotoxic effects.

Cutworms

Cutworms are dingy, grayish-black, smooth "worms" that are the larval stages of several different moths. Cutworms are active at night and damage seedling sorghum by cutting the stalk just above ground level. Large numbers of cutworms may be found in fields where grass and weeds are abundant.

When cutworms are damaging a plant stand, an application of insecticide applied by air or ground usually will give adequate control. Best results are obtained when insecticides are applied in the late afternoon. If the soil is dry, cloddy or crusty at the time of treatment, control may not be as effective as in moist soil.

Greenbug

The greenbug is an aphid that sucks plant juices and injects a toxin into sorghum plants. The aphid is pale green and approximately 1/16 inch long with a characteristic dark green stripe down the back. Greenbugs often occur in damaging numbers under favorable conditions and may cause economic losses. The extent of greenbug damage in sorghum is dependent upon greenbug numbers, plant size, vigor and stage of plant growth, moisture conditions and effectiveness of parasites and predators. Producers are cautioned to observe plant conditions closely as well as greenbug numbers and damage. Damage at the seedling stage may result in stand loss. Greenbugs usually feed in colonies on the undersides of leaves. Characteristic reddened spots on the upper leaf surface and the occurrence of honeydew are associated with greenbug feeding damage.

Producers in areas of the state where greenbugs occur should consider planting greenbug-resistant sorghum hybrids to reduce damage. Producers should be aware that the primary type of resistance is tolerance, and should not expect plants to be free of greenbugs. However, resistant hybrids generally are infested with fewer greenbugs than susceptible hybrids. Damage thresholds for resistant sorghums are the same as for susceptible sorghums.

A new biotype of the greenbug has been identified based on its effect on varieties of sorghum that are resistant to biotype E greenbug. This biotype has been designated biotype I. The two biotypes do not differ in appearance and occur together in some sorghum growing areas of Texas. Sorghum hybrids resistant to biotypes C, E and I are available. Insecticides have similar effectiveness in controlling biotype I greenbug and other biotypes in the same localities.

Sorghum producers are urged to check fields carefully for greenbugs during the production season. Observations should be made of plant damage, greenbug numbers, beneficial insect activity and plant moisture stress. Guidelines for when to treat are given below and in the following table.

Treat plants up to about 6 inches in height when visible yellowing and reddening of the plant and greenbugs are observed and stand loss is probable. Larger plants up to the boot stage will tolerate more greenbugs than seedling sorghum. Control greenbugs on this size plant before any entire leaves are killed.

Yield reductions during the boot, flowering and grain development stages are dependent on greenbug numbers, length of time that greenbugs have infested plants and plant condition. High numbers on booting and older plants can cause yield reduction and weakened plants that may lodge at a later date. Greenbugs on boot to heading stage sorghum should be controlled when colonies are causing red spotting or yellowing of leaves and at the death of one functional leaf.

In the Texas Blacklands, insecticide applications are suggested if greenbugs are colonizing on the upper leaves of booting sorghum and tissue is dying. Plants can tolerate approximately 30 percent leaf loss before yield reduction occurs. After sorghum heading, indications are that greenbug numbers which cause the death of more than two normal sized leaves after flowering and before the hard dough stage should be controlled.

These general guides are based on the assumption that the greenbug density increase is occurring so rapidly that control by beneficial insects is not effective. However, if more than 20 percent of the greenbugs appear brown and swollen from being parasitized, then application of an insecticide is not generally necessary. Also, plants undergoing drought or other stress cannot support as many greenbugs without suffering yield reductions.

The following table will serve as a general guide in determining the need for treatment:

Scouting Procedures for Greenbugs

Scouting sorghum for greenbugs is easy to learn and master. As in other types of field scouting, persons scouting for greenbugs need to collect information that will permit them to make reliable treatment decisions.

A minimum of 40 randomly selected plants per field should be examined each week. Greenbugs are seldom evenly distributed across a field, so examine plants from all parts of the field. Avoid examining only field borders. Examine a greater number of plants in fields larger than 80 acres or if making a control decision is difficult.

Consider these factors when making a control decision: number of greenbugs per plant, leaf damage, percent parasitized greenbugs (mummies), appropriate number of greenbug predators per plant and overall crop condition. When estimating the number of greenbugs absolute accuracy is not necessary because treatment decisions cannot be based on numbers alone. However, it is important to know if these numbers are increasing or decreasing from week to week. For instance, if the recommended treatment level (based on leaf damage) has been reached but greenbug numbers have declined substantially from previous observations, chemical treatment would not be justified.

In seedling sorghum (up to about 6 inches tall), greenbugs may be found on any part of the plant including the whorl, or under some environmental conditions, in the soil at the base of the plant.

When scouting seedling sorghum, examine the entire plant and the soil around the base of the plant. Note the presence or absence of greenbugs and any damage to plants (yellowing, death of tissue).

When scouting fields with larger plants, whole plant and soil inspections are not necessary. Greenbug colonies generally originate on the undersides of lower leaves and move up the plant. Only the undersides of lower leaves need to be examined. A word of caution: The development of greenbug colonies does not always follow this pattern on some sorghum hybrids. In some cases, greenbug colonies may first be found on the undersides of upper leaves. Take care not to confuse the bluish-green corn leaf aphid often found in the plant whorls with greenbugs.

To make a correct control decision, record and consider the previously listed factors and consult the recommended treatment levels provided. When estimating leaf damage, consider any leaf which has more than 75 percent of its surface reddened or damaged to be a dead leaf. Take care not to mistake the natural senescence of the small bottom "seed" leaves for greenbug damage. Estimate an average leaf damage level for the entire field unless it is feasible to spot treat.

Some insecticides with systemic action applied at planting for soil pests will also suppress greenbugs. (See page 4).

Corn Leaf Aphid

High densities of this bluish-green aphid, characterized by black legs, cornicles and antennae, sometimes cause damage to seedling sorghum. Larger sorghum plants in the boot and later growth stages generally can tolerate large numbers of aphids without significant damage. After panicle exertion, corn leaf aphid numbers rapidly decline. Yield losses have occurred only where corn leaf aphids cause stand loss of seedling plants. Although rare, head infestations have caused harvesting problems. These aphids feed primarily in the whorl of pre-boot sorghum and do not inject a toxin. Corn leaf aphids are important hosts for development of beneficial insects which are helpful in the control of greenbugs and other pests of sorghum.

Yellow Sugarcane Aphid

This lemon-yellow aphid is covered with small spines and has two double rows of dark spots down the back. The yellow sugarcane aphid has a wide range of wild hosts and is often found on johnsongrass and dallisgrass in Central and South Texas. During feeding, this aphid injects a toxin during feeding which causes purple-colored leaves in seedling plants, and stunting and yellowing of more mature leaves. It has caused death of pants in the pre-boot stage. Some systemic insecticides (such as disulfoton, terbufos, or carbofuran) applied at planting will suppress the development of yellow sugarcane aphid infestations. Otherwise, infestations typically occur soon after plants emerge from the soil. Consequently, fields should be scouted and plants inspected beginning the first week of plant emergence and twice weekly until plants have at least five true leaves. Yellow sugarcane aphid injury to sorghum is most severe when plants are small. As plants grow larger they become more tolerant to yellow sugarcane aphid feeding. Very small seedling sorghum plants (1 to 3 true leaves) are often significantly damaged after being infested for one week or less. The economic injury levels presented in the following tables are based on percent yellow sugarcane aphid infested plants when the infestation occurs at the 1, 2 or 3 true-leaf stage. Do not count the two cotyledon leaves which first appear. To use the tables, determine the cost of control per acre (both the insecticide and cost of application per acre); then estimate the expected per acre value of the crop based on production experience. Match the appropriate columns in the table, reading down for crop value and across for control cost. The value found is the percentage of yellow sugarcane aphid infested plants that would cause economic damage sufficient to justify the cost of control.

Yellow sugarcane aphid feeding on seedling sorghum causes a purple or yellow leaf discoloration. By the time plant discoloration symptoms are readily visible plants have already been significantly injured. However, discoloration symptoms may be useful in assessing yield loss that might be used in a decision to replant. Table 4 describes plant damage and the corresponding percent yield loss associated with that level of damage.

Chinch Bugs

Chinch bugs are sporadic pests of sorghum in Texas. The black bodied adult chinch bug has reddish-yellow legs and fully developed wings. The mostly white wings are marked with a triangular black spot at the middle of the outer wing margin. Immature chinch bugs resemble adults in shape but lack wings and are reddish in color with a white band across the back.

Adult and immature chinch bugs suck plant juices and cause leaf reddening. Wilting and severe stunting of plants attacked by chinch bugs have been noted from the time of seedling emergence until plants are 18 inches high. Chinch bugs are favored by hot, dry weather, and large numbers of immature bugs often migrate from wild bunch grasses or small grains to congregate and feed behind the lower leaf sheaths of sorghum plants.

Apply insecticide treatments when two or more adult chinch bugs are found on 20 percent of the seedlings less than 6 inches high. Make at least five random checks per field. Chinch bugs often feed below the soil surface especially in loose, dry soil. Carefully examine the base of the plants below the soil line for chinch bugs. On taller plants, initiate control when immature and adult bugs infest 75 percent of the plants. Aerial application is seldom effective and not recommended. When using ground application equipment, insecticide applications should be made through nozzles directed at the infested portion of the plants. Satisfactory control is seldom obtained on booting or larger plants.

Systemic insecticides applied at planting for soil insect pests will also suppress the development of chinch bugs. In fields with a history of economically damaging infestations of chinch bug, treatments with at-plant, soil incorporated insecticides may be justified. Granular products must receive about 1/2 inch of rainfall after application to be effective in the suppression of early season chinch bug infestations. If chinch bug infestations reach the economic threshold after plant emergence, post-emergence insecticide treatments may be justified.

Banks Grass Mite

High numbers of Banks grass mites have been observed on sorghum in the more arid areas of Texas. Newly hatched, light colored mites become dark green after feeding on sorghum. Mites have sucking mouthparts that withdraw plant fluids. Mites also produce webbing that can cover the undersides of leaves and the sorghum head during periods of heavy infestation. Although mites can be observed early in the growing season, density increases generally occur after the boot stage of development. Mites normally become established on the undersides of lower plant leaves. Mites migrate upward and sometimes move into sorghum heads as mite density and plant damage increase. Extremely high densities produce extensive webbing on sorghum heads and may be associated with stalk rot and lodging. Periods of hot, dry weather favor rapid mite population increase. Plants will tolerate mite damage better if protected from water stress. Heavy irrigation after mites increase will not suppress mite abundance.

Mite density and plant growth stage will dictate the need for miticide applications. Research has shown that large numbers of mites can reduce the ability of sorghum plants to make grain only until the seed reaches hard dough stage. However, yield losses may still occur after hard dough stage due if mites cause lodging and related harvest losses. In some areas (Trans-Pecos and High Plains), all recommended miticides have given erratic control at times. Thorough coverage is required; apply at least 3 to 5 gallons of spray mix per acre.

Sorghum Midge

The sorghum midge is one of the most damaging insects to sorghum in Texas. The adult sorghum midge is a tiny, fragile looking, orange fly. Larvae hatch from eggs deposited by a female midge in spikelets of flowering sorghum heads. Each female deposits about 50 tiny, yellowish white eggs during her short lifetime of less than 24 hours. An orange maggot hatches from the egg and feeds on the newly fertilized ovary, thereby preventing kernel development.

Effective sorghum midge control requires the integration of several control practices that reduce midge population density and their potential to cause crop damage. Planting hybrids of uniform maturity early enough to avoid late heading is strongly recommended. This practice allows sorghum to complete flowering before damaging midge densities build up. Cultural practices that tend to provide for uniform heading and flowering in a field are also important in midge control and in making decisions concerning the need for the insecticide applications. Eliminating johnsongrass inside and outside the field by cultivation and/or herbicide applications will also help suppress midge.

To determine the need for chemical control, an assessment of crop development, yield potential and midge density is required. Daily evaluation of these factors is encouraged during flowering.

Because midges lay eggs in flowering sorghum heads (yellow anthers exposed on individual spikelets), damage can occur until the entire head or field of sorghum has flowered. The period of midge susceptibility may last from 7 to 9 days (individual head) to several weeks (individual field) depending on the uniformity of flowering. A map is provided as a guideline to midge damage associated with time of sorghum flowering.

To determine the presence of sorghum midges, fields should be inspected mid-morning to shortly after noon when midge are most abundant on flowering heads. Each day a new midge brood appears, so inspect fields daily. Midge adults can be seen crawling on or flying about flowering heads. The simplest and most efficient technique for detecting and counting sorghum midges is careful, close-range inspection of all sides of a randomly selected flowering head. Panicles should be handled carefully during inspection to avoid disturbing the ovipositing midges. Other methods, such as placement of a clear plastic bag or jar over the panicle as a trapping device, appear to be less accurate than direct inspection of the panicle.

Because they are relatively weak fliers and rely on wind currents to aid their dispersal, adult sorghum midges are usually most abundant along field borders. For this reason, field scouts should first inspect plants along field borders, particularly those upwind. If few midges are found in these areas, there should be little need to sample the entire field. However, if sorghum midge numbers in upwind border areas equals or exceeds the economic threshold, at least 40 additional heads from the whole field (avoiding plants within 150 feet of field borders) should be inspected. Average sorghum midge abundance should then be calculated based only on these additional samples. A sample area should be no larger than 80 acres; larger fields should be divided.

The need to apply insecticidal control is based on the number of adult midges during the flowering period. Use the economic injury levels for susceptible or resistant sorghum hybrids as presented in the following tables. The density of adults per panicle that would justify chemical control can be determined by first estimating the per acre value of the crop, which is based on the condition of the crop at that time, and historical experience. Second, determine per acre cost of control, which includes both the cost of the insecticide and cost of application. Read down columns for cost of control. The density of adult midges at that point in the table would cause damage sufficient to warrant the cost of control. As an example, if the market value of the crop is $200/acre and the cost of control is $6.00/acre, an average midge density of 1.2 midges per panicle (head) or greater would warrant insecticide treatment. If adults are still present 3 to 5 days later, immediately apply a second treatment. If midges are present the day following treatment, it does not mean you do not have protection for the heads; midges could be re-infesting the field, which is common. Several insecticide applications at 3-day intervals may be justified in the yield potential is high and midges are abundant.

Midge-resistant sorghum hybrids are commercially available and, within limits, provide an additional management tool. At similar infestation levels of ovipositing midge females, resistant hybrids generally suffer one-fifth the damage that susceptible sorghum hybrids suffer. Resistant hybrids have economic injury levels five times higher than susceptible hybrids. When adult midge densities exceed the economic injury level during flowering of resistant hybrids, insecticide applications at 5-day intervals are required.

Sorghum Webworm

The sorghum webworm occurs primarily in the more humid eastern half of the state.

Webworm larvae are reddish to yellowish-brown, somewhat flattened and marked with four longitudinal reddish to black stripes. Larvae are approximately 1/2 inch long when mature and are densely covered with spines and hair.

Large numbers of webworms can occur, especially in late planted sorghum. They gnaw circular holes in maturing grain and feed on the starchy contents.

Plowing under crop residues to destroy overwintering larvae and early planting are important cultural control practices.

Make frequent head inspections when sorghum is beginning to flower and continue at 5-day intervals until hard dough. To examine heads for sorghum webworm, shake sorghum panicles vigorously into a 5-gallon plastic bucket. Larvae can then be seen and are easily counted in the bucket. This "beat-bucket" technique permits detection of even small larvae (less than 1/4 inch long), which are commonly overlooked. At least 30 plants from the whole field should be inspected to ensure reasonable reliability of sample results. Fields larger than 80 acres should be divided into portions no larger than 80 acres. Insecticide application is suggested when five or more small larvae are found per head.

Fall Armyworm - Corn Earworm
(Whorlworm and Headworm)

Fall armyworm and corn earworm moths often deposit eggs on the leaves or heads of sorghum. Larvae of these moths vary in color from pale green to almost black, with longitudinal stripes running along the back.

Whorl. On preheaded sorghum, corn earworm and fall armyworm often feed in the plant whorl. As leaves emerge from the whorl, "ragged shot hole" damage is evident. Although this damage may be dramatic, control of "worms" in the whorl stage seldom is economically justified. Chemical control may be necessary if examination of larval feeding indicates damage to the developing head or growing point.

Heading. Larvae may also attack developing sorghum heads. Corn earworms are cannibalistic, which influences the number of larvae usually found per head.

Early planting and practices that encourage the development of beneficial insect populations aid in the control of armyworms and earworms. Planting "open-headed" sorghum hybrids also tends to reduce the occurrence of larvae in sorghum heads. Sorghum head inspections should begin soon after flowering and continue at 5-day intervals until hard dough. To examine heads for fall armyworm-corn earworm larvae, shake randomly selected sorghum panicles vigorously into a 5 gallon plastic bucket. Larvae can then be seen and are easily counted in the bucket. This "beat-bucket" technique permits detection of even small larvae (less than 1/4 in long), which are commonly overlooked. At least 30 plants from the whole field should be inspected to ensure reasonable reliability of sample results. Fields larger than 80 acres should be divided for sampling into portions no larger than 80 acres. To determine the economic injury level see the chart below. [Example: If your crop is valued at $200 per acre and the cost of control - insecticide and application - is $8 per acre, then the economic threshold is an average 1.0 larva per head.]

Panicle-Feeding Bugs

Several species of true bugs, primarily stink bugs, may move from alternate host plants into sorghum in relatively large numbers during grain development. Bugs infesting sorghum in Texas include the rice stink bug, southern green stink bug, conchuela stink bug, brown stink bug, red shouldered stink bug, leaf footed bug and false chinch bug. Panicle-feeding bugs feed mainly on seeds and to a lesser extent on other panicle parts and may cause economic damage. Extent of damage depends on the number of bugs per panicle, duration of infestation and stage of grain development when infestation occurs. Bugs cause more damage early during grain development and less damage as grain develops to the hard dough stage. Both nymphs and adults may cause damage, reducing grain weight, quality and seed germination. Panicle-feeding bugs tend to congregate in clumps within a field.

The number of bugs per panicle which will reduce grain yield varies depending on the bug species and stage of grain development when infestation occurs.

Another type of panicle-feeding insect that is an occasional pest is the false chinch bug. Although smaller in size, the false chinch bug is similar in appearance and habits to the chinch bug. False chinch bugs have sucking, stylet-type mouthparts and feed chiefly on sorghum heads. Reduced seed weight and quality result from false chinch bug feeding. These insects often are clumped, making spot pesticide applications only to infested field areas possible. Chemical applications should be made when an average of 140 false chinch bugs per head are found.

Not all stink bug species found in sorghum are economic pests. Several species prey on harmful insects and thus are beneficial.

There is currently no satisfactory technique for estimating the total number of panicle-feeding bugs per plant; however as these insect pests tend to congregate in the sorghum head, an estimate of the average number of bugs per panicle should provide a good indication of the need for treatment. The beat-bucket technique can be used to estimate the average number of bugs per head. Sorghum panicles should be shaken vigorously into a 5 gallon. Adult stink bugs can then be more easily seen and counted in the bucket. The scout should be alert for adult stink bugs flying from the sampled plant or from the bucket and look for bugs on plant leaves and weeds within the field to maintain an accurate estimate of the total number of bugs per sorghum plant. At least 30 plants from the whole field should be inspected to ensure reasonable reliability of sample results. Fields larger than 80 acres should be divided into portions no larger than 80 acres.

To determine the profitability of controlling an infestation of rice, southern green or conchuela stink bugs or leaf-footed bugs, calculate the per acre control cost (insecticide and application) and the expected per acre market value of the grain (yield x price). Next, determine the approximate grain development stage when the infestation occurred. If the estimated stage of development is hard dough and the infestation level per panicle is 16 bugs or fewer, do not control bugs. For bug infestations beginning at the milk or soft dough stages, consult the economic injury level tables. Economic injury levels for infestation (rice stink bugs per panicle) at which control is justified are indicated for various control costs and market values. The economic threshold level for false chinch bug is 140 bugs per panicle when infestations begin at the milk stage of grain development. Economic thresholds for the rice stink bug, southern green stink bug, conchuela stink bug and leaf-footed plant bug are given in Tables 5, 6 and 7, 8 and 9, 10 and 11, and 12 and 13, respectively.

For additional information on panicle-feeding insects refer to B-1421, Suggested Guide for Controlling Panicle-Feeding Bugs in Texas Sorghums.

Sugarcane Borer - Southwestern Corn Borer

These closely related pests of sorghum, corn and other crops damage plant stalks by their tunneling activity. Buff colored adult moths lay eggs in shingle-like arrangements on the leaves and stalks of host plants. Young larvae of the sugarcane and southwestern corn borer are creamy white and marked with brown to black spots. The more more mature overwintering larval stage are less distinctive spots, or no spots. Larvae overwinter in the stalks or root crowns of sorghum plants and other crop debris.

Borer-infested stalks are reduced in diameter and plant lodging often results. Borer damage also causes dead heart, kills the whorl of the plant, and increases susceptibility to stalk rotting diseases.

Cultivation practices that destroy stalks, expose larvae and bury crop residues greatly reduce borer populations. Rotation with non-host crops and early planting of sorghum also aid in control of the sugarcane and southwestern corn borer.

Endangered Species Regulations

The Endangered Species Act is designed to protect and recover animals and plants that are in danger of become extinct. Under the provisions of this Act, the U.S. Fish and Wildlife Service assists the Environmental Protection Agency and the Food and Drug Administration in implementing pesticide programs by conducting biological analyses of the effects of pesticides on threatened and endangered species. Many pesticide labels now list restrictions limiting the use of products or application methods in areas designated as biologically sensitive. These restrictions continue to change. Refer to Environmental Hazards of Endangered Species discussion sections of product labels and/or call your local county Extension agent of Fish and Wildlife Service personnel to determine what restrictions apply to your area. Regardless of the law, pesticide users can be good neighbors by being aware of how their actions may affect people and the environment.

Protecting Bees and Other Pollinators from Insecticides

Pollination is important in producing many seed crops. This is particularly true for legumes such as alfalfa, clovers and vetch. Most grassy plants are wind- or self-pollinated and do not require the assistance of insect pollinators. Where pollen collecting insects are required for flower fertilization, the producer, insecticide applicator and beekeeper should cooperate closely to minimize losses of bees. Sorghum is an important source of pollen for honey bees in many locations in Texas. The following guidelines will reduce bee losses:
1. Apply insecticides, if practical, before bees are moved into fields for pollination.
2. Where insecticides are needed, use materials least toxic to bees.
3. Make all applications when bees are not foraging in the field. Evening or early morning treatments between the hours of 7 p.m. and 6 a.m. generally are more satisfactory. Evening applications, after bees have left the field, are less hazardous than early morning applications.
4. Use spray or granular formulations.
5. Where it is necessary to use an insecticide from groups 1 or 2 in the following list, notify beekeepers so they can make necessary arrangements to protect their bees.
6. To prevent heavy losses of bees, avoid drifting or spraying any insecticide directly on colonies. Bees cluster on the fronts of their hives on hot evenings. Pesticide drift or direct spray at this time generally results in high mortality.

Fig. 3. Sorghum Pest Occurrence Profile

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

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

Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, Texas Agr icultural Extension Service. the Texas A&M University System.

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