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identification of soybean insect

identification of soybean insect

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Soybean insects Document Transcript

  • 1. Stem Borer - Life cycleThe adult soybean stem borer lays eggs from June through August in the leaf petioles at mid-canopy. Theeggs hatch into white or yellow grub-like larvae which tunnel down the petioles and into the stems.This tunneling causes the leaves to wilt and eventually fall off the plant after the larva enters the main stem.Larvae usually will have tunneled to the base of the plant by the time the plants reach physiological maturity.Once the larva reaches the base of the plant they can girdle plants internally, often causing the entire plantto fall over (lodge) .The larvae overwinter below ground in the base of the root. Larvae pupate in the spring and adults emergeto begin the cycle again.Since this is a native insect it also has several wild hosts including cucklebur, rag weed, and wild sunflower.It has also been reported as a pest of cultivated sunflower where it has been referred to as the sunflowerstem girdler.© Plant Health Initiative 2009 All Rights Reserved.Home | Site Index | For Researchers | Contact Your Local ExtensionStem Borer - ScoutingWhite or yellow grub-like larvae tunnel downthe petiole into the soybean stem.Photo by Phil Sloderbeck © Kansas StateUniversityInsect-induced lodging. The plants willoften be broken off smoothly at the soilline. Photo by Phil Sloderbeck, ©Kansas State University
  • 2. A good way to recognize stem borer infestations is to look forindividual wilted or dying leaves in the middle of the canopyduring mid summer. Infestations can be confirmed by splittingthe stems and looking for tunneling and larvae.Later in the season, look for lodged plants. The plants will be broken off smoothly near the soil line. Thesurface of the break on the stubble (the upper face of the roots) will be smooth and often show no sign oftunneling . This is because the larvae tend to plug the tunnel above them after they girdle a plant. Therefore,if you see lodged plants with no obvious cause, split stem bases and see if signs of tunneling and a stemborer larva can be found.Stem bases can also be split after harvest to get an idea of the infestation that had been present in the fieldduring the growing season.Stem Borer - ManagementTimely harvest in infested fields is extremely important to prevent yield loss due to lodging. Rotation can bean effective management tool where soybean acreage is limited. Rotate soybeans with non-host crops andcontrol host weeds such as ragweed and avoid rotating soybeans with sunflowers. However, this option haslimited value were soybeans are commonly grown in an area and populations have reached damaginglevels as the adults can fly and readily disperse to near by fields.Burial of stem borer infested stubble by plowing, row bedding or disking in the fall to a depth of 2 inches issufficient to decrease larval survival and adult emergence. Thus the importance of this pest may increasewith increases in no-till acreages.Research is in progress to identify resistant or tolerant soybean varieties and to investigate insecticidetreatment options, however to date insecticides have not been shown to be effective at controlling this pestand resistant varieties have not been identified.The first sign of damage from thesoybean stem borer are wilted leavesthat have been tunneled as the larvaemove from the leaf petiole into the mainstem.Photo by Phil Sloderbeck, © KansasState UniversityLarvae of the soybean stem borer.Photo by Phil Sloderbeck, © KansasState University
  • 3. Other Insect Pests of SoybeanThese insects can be sporatic pests in soybean fields.Imported longhorned weevilThe weevils are found on soybean in late June to early July, when they feed onleaf tissue and smaller veins. Their feeding causes a ragged, scalloped leafborder and tends to be found mainly on field margins. The adult weevils aresmall, mottled gray in color and do not fly.Japanese beetleJapanese beetles are found in the more southern areas of the region. They areeasy to identify with their metallic green and copper-coloring, about 3/4 inch inlength. They feed mid-June through August.Japanese beetles can be voracious feeders but tend to congregate in certainareas. Be sure to scout the entire field to determine the extent of the damage.Seedcorn maggotThe seedcorn maggot are soil-inhabiting, yellow larvae about 1/4inch long. They feed on newly planted soybean seed. The adultflies prefer to lay their eggs in fields containing freshly decayingorganic matter. Damage is most likely to occur during a cool, wetspring when seed germination is slow.Soybean looperThe soybean looper is a caterpillar about 1 1/4 inches long thatmoves with the characteristic looping movement. It is a sporaticfeeder on soybeans, usually found mid-July to mid-August. Thelarvae eat leaf tissue, leaving irregularly-shaped holes between theveins. .Thistle caterpillarThistle caterpillars are bristly, black and yellow larvae of thepainted lady butterfly. They feed on soybeans in July and August,causing minor defoliation. The second generation will feed on thetop layer of leaves and will web the leaves together with silk.
  • 4. WhiteflyWhiteflies are tiny white flies and powdery wings that arecommon pests of greenhouse plants. They are minor pests onsoybeans, but can be confused with soybean aphids. Be sure youcan distinguish between the two insects.Biology of Binodoxys communisContributed by Camila Botero, University of WisconsinBinodoxys communis is a tiny non-stinging parasitoid wasp that parasitizes and ultimately kills soybeanaphids. It belongs to the insect order Hymenoptera (ants, wasps, bees and sawflies), and is in the familyBraconidae. Many braconid wasps are considered beneficial because they help control agricultural pests,and they are one of the most important groups of natural enemies of aphids.Entomologists have identified parasitoids as possible agents for classical biological control of the soybeanaphid. One of the most promising candidates is Binodoxys communis, which is being tested in field researchin the U.S. and in Asia to evaluate the relative risks and control potential.The primary focus of work in the2008 field season was rearing, releasing, and monitoring the establishment of the parasitoid wasp in 6midwestern states.Life Cycle of B. communisLike all parasitoids, B. communis uses an egg-laying organ called the ovipositor to lay a single egg insideeach aphid host. When the egg hatches, the legless cream-colored larva starts feeding on the aphid’s bloodBinodoxys communisPhoto credit: Camila Botero, Universityof WisconsinAn aphid killed by the parasitoid,Binodoxys communis.Photo credit: Dan Mahr, University ofWisconsin
  • 5. and organs. As it consumes the aphid from the inside out, the larva grows and develops through severalstages ultimately killing its host. Because it feeds internally within the aphid, it is called an endoparasitoid.When the parasitoid larva finishes feeding, the only part remaining of the aphid is its empty skin, whichappears puffed up, brown and hardened. The “mummy”, as the shell of the dead parasitized aphid is called,is usually formed 6 to 8 days after parasitization, and this is where the larva pupates and transforms into anadult. In the pupating process the parasitoid larva glues the mummy to the plant surface and spins a cocooninside where it remains protected. Four to six days later, the adult wasp chews a round hole in the aphidshell and emerges from it. After emergence, males seek females for mating and females start seekingsuitable aphid hosts to attack.Females have the potential to lay up to 200 eggs, depending on the temperature, humidity, parasitoidpopulation density, and soybean aphid numbers and quality. Adults feed only on water, flower nectar, honeydew, or other sugar sources. Many parasitoid species have been observed on floral nectar in fields, andresearch suggests that crops with nearby flowering vegetation have higher parasitism rates.The whole process from egg to adult emergence takes between 10 and 14 days, and adults live about 10days. Since females start reproducing almost immediately after emergence, it takes about 10 to 14 days foran entire generation to be completed. The number of generations per year is not yet known.The overwintering habits of B. communis are also not yet known, and this is currently an area of activeresearch. Scientists think the parasitoid either disperses with the soybean aphid to buckthorn or it uses analternate aphid host, otherwise it would not survive after soybean is harvested or when it is not available.Control of soybean aphids by B. communisResearch suggests that B. communis is most effective as a natural enemy under low soybean aphiddensities, and as aphid numbers increase, the amount of parasitization decreases. This may be becausedense aphid colonies tend to attract predators (particularly Asian lady beetles) which not only prey onsoybean aphids but on parasitized aphids and mummies as well. Therefore, B. communis might be mosteffective in early season when soybean aphid numbers are low, preventing high density aphid colonies frombuilding up in soybean fields.How to scout for B. communis in the fieldB. communis is smaller than a pinhead and usually walks or makes small flights throughout soybean plantssearching for suitable hosts. It is difficult to see in the field, so the best and more reliable way to determineits presence is by searching for its mummies. The advantage of searching for mummies rather than for theCheck soybean leaves for thepresence of aphid mummies - asign of parasitoids at work.Photo credit: University ofMinnesota
  • 6. adult is that they are easy to see, they conserve their shape, and they stay attached to the plant even afterthe adult parasitoid has already emerged from it.Conservation of Natural Enemies of Insect PestsConservation biological control is protecting the natural enemies that are already present.Providing food, water and shelter for natural enemies will encourage them to stay in the crop area to feedand reproduce. Beneficial insects often need an alternate food supply in addition to the pest prey. Manynatural enemies, including the adult lacewing and minute pirate bug must have a source of nectar, pollen orhoneydew to feed on in the general vicinity of the pest. This will stimulate egg laying in the crop.A more diverse landscape tends to harbor many more natural enemies than a large-area monoculturebecause it offers more food, water, and shelter to beneficials. Consider how you might supply theseresources near your fields. Small patches of unmowed grass and flowering plants can provide a food sourceas well as sheltered, humid spots where beneficial insects can hide during the day without dehydration. Amanaged boundary around fields is also a good way to control weeds and provide overwintering sites forbeneficials.Careful use of insecticides is important to conserve natural enemies. Most insecticides kill beneficial insectsas well as the target pest. Reduce the overall use of broad spectrum insecticides when possible and treatLady beetles feeding on soybeanaphids.Photo credit: University of WisconsinLarvae of the green lacewing arecommon predators of insect pests infield crops.Photo credit: Peter Sonnentag,courtesy Eileen Cullen, University ofWisconsin
  • 7. only when necessary based on economic injury thresholds of the pest. Use the least distruptive productavailable, and apply at a time and place that is the least injurious to beneficial insects.Scouting GuidelinesDiseases and insects show up at different, often predictable times during the growing season. In general,scouting for insects is based on the time of the year and crop development stage, while scouting fordiseases is based mainly on the crop development stage.
  • 8. Disease / Pest Growth stage toscoutBest time to scout Best place to scoutSoybean AphidAlso look for antsand ladybirdbeetles.V1-2 . Scout twotimes per weekduring this timeperiod. Continuescouting throughpod set.In early July, start scouting tobecome familiar with the aphidpressure in your fields. Use a handlens or other magnifier.V1-2: Under young upper leaves, petioles,and stem.Vn: new branches in the lower canopy.R1-R4: undersides of mid-canopy leavesand stems.Bean leaf beetle First-generationpeak in late V orearly R stage.Second-generationpeak during pod-fill stage.Early July (first generation)August (second generation).Bean pod mottlevirusmaturity at harvest check seedBrown stem rot full pod late August not specificGrasshoppers any stage July through September border rows near weedy or grassy areasGreen stem maturity at harvestPhytophthoraroot or stem rotvegetative stages July and August Wet and waterlogged soils. Compactedsoil.Seedling blightPythium orFusariumbefore V2 late May or when soil temperaturesare cold (<60°F)low and wet spotsSeedling blightPhytophthora orRhizoctoniabefore V2(late planted)mid-June or when soiltemperatures warm to 70-80°F.low and wet spotsSoybean CystNematode6 weeks afterplanting up until 3to 4 weeks beforeharvest.Easier to observe on soybeanroots early in the season.A suspect area:a field entrance, areas that had flooded,weedy areas, lower yielding areas.Soybean mosaicvirusmaturity at harvest check seedSpider Mites any stage July and August, especially duringperiods of droughtplants near the edges of the fields orwhere soybeans are stressedStem borer late V, early R mid-summer Individual wilted or dying leaves in themiddle of the canopy.Later in the season, look for lodgedplants.Sudden deathsyndromepod setting after mid-August high-moisture areas in fertile fieldsWhite moldmushroom(apothecia)at canopy closure last week of June,1st week of July,varies with row spacinghigh soil moisture areas, especially duringflowering.Areas where moisture collects due to fogs,extended dew periods and pockets of poorair drainage.White-mold-infested plantspod setting August-September visibly dead plantsSoybean viruses maturity at harvest check seed
  • 9. Scouting GuidelinesDiseases and insects show up at different, often predictable times during the growing season. In general,scouting for insects is based on the time of the year and crop development stage, while scouting fordiseases is based mainly on the crop development stage.
  • 10. Disease / Pest Growth stage toscoutBest time to scout Best place to scoutSoybean AphidAlso look for antsand ladybirdbeetles.V1-2 . Scout twotimes per weekduring this timeperiod. Continuescouting throughpod set.In early July, start scouting tobecome familiar with the aphidpressure in your fields. Use a handlens or other magnifier.V1-2: Under young upper leaves, petioles,and stem.Vn: new branches in the lower canopy.R1-R4: undersides of mid-canopy leavesand stems.Bean leaf beetle First-generationpeak in late V orearly R stage.Second-generationpeak during pod-fill stage.Early July (first generation)August (second generation).Bean pod mottlevirusmaturity at harvest check seedBrown stem rot full pod late August not specificGrasshoppers any stage July through September border rows near weedy or grassy areasGreen stem maturity at harvestPhytophthoraroot or stem rotvegetative stages July and August Wet and waterlogged soils. Compactedsoil.Seedling blightPythium orFusariumbefore V2 late May or when soil temperaturesare cold (<60°F)low and wet spotsSeedling blightPhytophthora orRhizoctoniabefore V2(late planted)mid-June or when soiltemperatures warm to 70-80°F.low and wet spotsSoybean CystNematode6 weeks afterplanting up until 3to 4 weeks beforeharvest.Easier to observe on soybeanroots early in the season.A suspect area:a field entrance, areas that had flooded,weedy areas, lower yielding areas.Soybean mosaicvirusmaturity at harvest check seedSpider Mites any stage July and August, especially duringperiods of droughtplants near the edges of the fields orwhere soybeans are stressedStem borer late V, early R mid-summer Individual wilted or dying leaves in themiddle of the canopy.Later in the season, look for lodgedplants.Sudden deathsyndromepod setting after mid-August high-moisture areas in fertile fieldsWhite moldmushroom(apothecia)at canopy closure last week of June,1st week of July,varies with row spacinghigh soil moisture areas, especially duringflowering.Areas where moisture collects due to fogs,extended dew periods and pockets of poorair drainage.White-mold-infested plantspod setting August-September visibly dead plantsSoybean viruses maturity at harvest check seed
  • 11. B-1501Managing Soybean InsectsDawn H. GougeAssistant Professor and Extension EntomologistMichael O. WayAssociate Professor, Texas Agricultural Experiment StationAllen KnutsonProfessor and Extension EntomologistGreg CronholmExtension Agent-IPMCarl PatrickProfessor and Extension EntomologistThe Texas A&M University System
  • 12. CONTENTSPest Management PrinciplesVariety Selection and Early Soybean Production SystemsInspecting Soybean Fields for Insects and Damage• Ground cloth method• Vertical beat sheet method• Sweep net method• Plant damageSoybean Growth and DevelopmentSeedling and Early-Season Pests• Threecornered alfalfa hopper• Saltmarsh caterpillar• Woolly bear caterpillar• Armyworm and beet armyworm• Lesser cornstalk borer• CutwormMid- to Late-Season Pests• Threecornered alfalfa hopper• Foliage-feeding pests
  • 13. Late-Season and Pod-Filling Pests• Armyworm• Stink bugs• Corn earworm• Soybean stem borerOccasional PestsBiological ControlMicrobial Insecticides and Insect Growth RegulatorsInsecticide Application MethodsProtecting Bees and Other Pollinators from InsecticidesPolicy for Making Chemical Control RecommendationsSoybean Insect Control Suggestions (chart)Conversion TableFunding for this publication was provided by the Texas Soybean Board.Managing Soybean InsectsMany insects feed on soybeans and can threaten yield and/or quality. However, thefrequency and severity of pest damage vary considerably between production areas--evenwithin and between fields-- and from season to season. (In Texas, the Gulf Coast andLower Rio Grande Valley counties are most likely to experience economic losses.)Therefore, it is important to inspect plants regularly and base control decisions onestablished economic thresholds or action levels.Pest Management PrinciplesThe term integrated pest management (IPM) applies to a philosophy used in the designof insect, mite, dis-ease and weed control programs. IPM encourages the use of the mostecologically sound combination of effective pest suppression techniques. The IPMconcept assumes that pests can be tolerated to some degree unless they cause economicloss. The first line of defense against them is prevention through the use of goodagronomic practices or cultural methods that discourage pest population development.Control measures are implemented only when pest populations reach levels at which cropdamage could result in losses greater than the cost of the treatment. This is called theeconomic threshold level or action level. Regular field scouting helps determine if and
  • 14. when that level is reached. Precise timing and execution of each production operation isessential. In short, IPM strives to optimize rather than maximize pest control efforts.The economic thresholds or action levels presented in this publication should be usedonly as rules of thumb. Several factors affect the level of damage soybean plants cantolerate before the cost of a control tactic (such as the use of an insecticide) becomesprofitable. These factors include the anticipated market value of the crop, anticipatedyield, and the cost of the treatment. In general, when the market value of soybeans is highand/or the cost of control is low, economic threshold levels may actually decrease (fewerpests or pest damage can be tolerated). Threshold levels presented here may also changewith the growing season, the presence of different pests, the type of damage, plant growthstage, and general plant vigor.Variety Selection and the Early Soybean Production SystemSome soybean varieties suffer more damage from certain pests (particularlycaterpillars) than others. Other varieties are resistant to or tolerant of several of the majordefoliating pests. Data on the yield potential for various soybean varieties in differentareas of the state are available from your county Extension agent.The Early Soybean Production System (ESPS) is a relatively new and popular methodof growing soybeans in Texas. The ESPS, as practiced on the Upper Gulf Coast and innortheast Texas, relies on planting early-maturing soybeans (Maturity Groups IV and V)in April and harvesting in September. In the conventional system, later maturingsoybeans (Maturity Groups VI, VII and VIII) are planted in May and June and harvestedin October and November. Generally, soil moisture is lowest on the Gulf Coast and innortheast Texas in July and August when conventionally grown soybeans are in thecrucial pod-fill stage of development. ESPS soybeans are usually beyond the pod-fillstage at this time. Adequate soil moisture allows ESPS soybeans to fill properly. Insectdamage also is affected by plant maturity. For instance, defoliating caterpillars usuallyattack conventionally grown soybeans from late August to mid- September when ESPSsoybeans are close to maturity and unattractive to insects. ESPS soybeans usually avoiddefoliator damage, but are often subject to stink bug infestations earlier in the season,beginning at bloom. For more information on the ESPS, obtain the Early SoybeanProduction System Handbook from your county Extension agent.Inspecting Soybean Fields for Insects and DamageInsect populations in soybean fields can change rapidly. Growers should check fieldsat least once and preferably twice a week to determine the species present, the pestdensity, and the amount of damage. Plant damage estimates are also useful in makingmanagement decisions.Ground cloth method: This technique is primarily used to survey for stink bugs andcaterpillars, but it is also useful for determining numbers of other species before and afterpesticide applications. This method uses an off-white cloth measuring 36 x 42 inches.
  • 15. Staple a thin strip of wood, approximately 1 inch wide, to each short side of the cloth.Select a random site in the field and unroll the cloth from one row over to the next row.Mark off 18 inches on each row bordering the cloth and vigorously shake all the plantswithin that area. Two 1.5-row-foot sections (3 feet total) will be sampled simultaneouslyfor insects. Count the number of insects that fall on the cloth. Repeat the process in atleast ten locations in the field (30 feet of row sampled) and total the counts to get thenumber of each species per 30 row feet. If the results show that populations are close tothreshold levels, or if the field is very large, sample more areas to increase confidence inthe results. This method is not useful in drilled or broadcast-planted soybean fields. Whenthe soil is wet another method may be more convenient.Vertical beat sheet method: The vertical beat sheet is another method of samplinginsect populations. This device is constructed of galvanized metal flashing, or similarlystiff material, 36 inches wide and crimped to provide a beating surface 34 inches tall anda collecting trough 4 inches wide. The trough is positioned at the base of row-plantedsoybean plants and arthropods are removed along 36 inches of row by shaking andbeating the foliage against the vertically positioned surface. Dislodged arthropods slideinto the trough where they can be counted in the field or poured into a container to becounted elsewhere. This method does not require kneeling down between the rows, andcan be used to sample weedy fields, fields with standing water in the rows, and narrow-row or drill-planted soybean fields. Economic threshold levels developed for thissampling method are for rowplanted soybeans only and should not be used if row spacingis less than 30 inches.Sweep net method: A standard 15-inch-diameter sweep net is often used for samplinginsects on soybeans. Make ten consecutive (180-degree) sweeps while walking throughthe field, swinging the net from side to side across the row with each step. Then identifyand count insects as they are removed from the net. Repeat the sampling procedure in atleast ten random sites and total the counts of each species per ten sweeps to determine thenumber of insects per 100 sweeps. Increasing the number of samples taken from a fieldincreases the accuracy of the population estimates. If the population estimates are close tothreshold levels, or if the field is large, sample more areas to increase the accuracy of theresults. Economic threshold levels developed for this sampling method are for row-planted soybeans only and should not be used if row spacing is less than 30 inches. Thesweep net, however, is one of the few methods of sampling arthropods in drill- orbroadcast-planted soybean fields.Plant damage: Insects damage soybean plants in four ways. Soil insects can feed ongerminating seedlings or roots, causing the plants to lose vigor, wilt or die. Aboveground, stems can be damaged by tunneling larvae or girdled by the threecornered alfalfahopper. Foliage can be damaged by chewing caterpillars and beetles, or by the feeding ofmites, aphids and thrips. Finally, pods can be hollowed out by corn earworms and seeddeformed and discolored by stink bug sucking damage. Estimating the level of insectdamage is essential in determining the need for control measures.
  • 16. Insects that feed on seedlings are important only if stands are damaged to the extentthat yields are reduced. Six to eight healthy seedlings per row foot are sufficient foroptimum yields. Uniform loss of seedlings is not as detrimental as the loss of allseedlings in portions of a row.Threecornered alfalfa hoppers girdle the main stems of soybean plants. This damagefirst appears as slight indentations and later as swellings encircling the entire main stem.Randomly selected row-foot sections, at several locations in the field, should beexamined for fresh damage early in the season (3- to 10-inch plants).Foliage loss from the feeding of caterpillars and beetles is estimated visually. Examinerandomly picked individual leaflets and estimate the percent leaf surface missing fromeach. Select an equal number of leaves from all levels of the plant canopy. Add theseestimates together and divide by the total number of leaflets examined to determine thepercent defoliation for the different areas of the sampled field. Research has shown thatslight leaf-feeding injury may actually increase the yield of late maturity group soybeans.Beyond an initial 10 percent leaf surface loss, however, every additional 10 percent losscan decrease yield by 2 bushels per acre. Yield loss from defoliation depends on thesoybean growth stage.Pod damage is not sampled directly. Insects that cause pod damage are sampled usingsweep net or ground cloth techniques.Soybean Growth and DevelopmentFrom seed germination to harvest, a soybean crop is under constant attack from avariety of insects. Soybean plants can compensate for substantial levels of insect injury,and yield can even improve with low levels of injury. Losses depend greatly upon thestage of plant growth, so pest economic thresholds vary with the stage of plantdevelopment.Soybean growth stages are designated by the letter V for vegetative or R forreproductive. There are two types of stem growth and flowering in soybeans. In theindeterminate stem type, grown mainly in the northern U.S., the terminal bud continuesvegetative growth during most of the season. The plant develops a sparse but evendistribution of pods on all branches. In the determinate stem type, grown mainly in thesouthern U.S., the terminal bud stops vegetative growth when it becomes a flower. Plantsdevelop a dense cluster of pods at the terminal.Seedling and Early-Season PestsThreecornered alfalfa hopper. This insect can be found in soybean fields from theseedling stage through maturity. During the seedling stage its feeding causes girdled mainstems; in later growth stages petioles are girdled. Plants damaged in early growth stagesmay not be noticed until they are much older and heavier. Because of the damaged stems,plants may lodge when stressed by wind, rain or cultivation equipment. The restricted
  • 17. flow of nutrients in girdled plants can reduce the number of pods produced. However,this type of damage rarely reduces yield because healthy plants adjacent to damagedplants compensate by producing higher yields. This is a phenomenon known as “plantstand compensation.” Main stem girdling is difficult to prevent with insecticideapplications. A better management strategy for this type of damage is to manipulateseeding rates in order to obtain at least six undamaged plants per foot of row.Figure 1. Soybean growth stages and development.
  • 18. Saltmarsh caterpillar. These large, hairy, yellow caterpillars occasionally move intofields from weed hosts early in the season. When numerous, their damage may causesome loss in plant stands near field margins. Spot or perimeter treatments may berequired if infestations threaten stands.
  • 19. Woolly bear caterpillar. These are hairy, black and red caterpillars that cause damagesimilar to the saltmarsh caterpillar.Armyworm and beet armyworm. Armyworms are conspicuously striped caterpillarsthat may occur locally in high numbers. Often they develop in pastures or roadsidevegetation and march en masse into fields, eating as they go. They also can developwhere moths lay eggs in the field. Young caterpillars feed close together, causinglocalized skeletonization and defoliation damage.Table 1. Soybean growth stages and accepted codes.Fehr and Caviness (1977)1 Plant developmentVE EmergenceVC Cotyledon + unfolding unifoliate leavesV1First node trifoliate leaves +photosynthesisV2 Second nodeV3 Third nodeV4 Fourth nodeV5 Fifth nodeV6 Sixth nodeV(n) Nth nodeR1 Beginning bloomR2 Full bloomR3 Beginning pod developmentR4 Full podR5 Beginning seedR6 Full seedR7 Beginning maturityR8 Full maturity leading to harvest1Fehr, W. R. and C. E. Caviness. 1977. Stages of soybean development. SR80, Iowa StateUniversity. The most modern refinement of this system is described in Ritchie, S. W., J.J. Hanway, H. E. Thompson and G. O. Benson. 1989. How a soybean plant develops.SR53, Iowa State University.Beet armyworms are green to brown with pale stripes along their sides, and aconspicuous black mark on each side of the body above the second pair of true legs. Theyprefer broad-leaved plants such as soybeans, and are generally more difficult to kill thanarmyworms because they are tolerant to certain insecticides.
  • 20. Armyworms and beet armyworms in the Gulf Coast region of Texas rarely causesufficient damage to warrant treatment. However, in the Texas Panhandle the beetarmyworm is the primary foliar feeding caterpillar pest in soybeans.Lesser cornstalk borer. Seedlings may be damaged by the lesser cornstalk borer.Larvae tunnel into the stem at the soil line, restricting the flow of nutrients to the upperportion of the plant and causing it to wilt and die. The very active, bluish-greencaterpillars have brown stripes and are found inside the stem or in a silken tube justbelow the soil surface adjacent to the stem. These pests are usually found only in welldrained, sandy soils; they thrive under dry conditions. Irrigation reduces potentialdamage. It is important to apply insecticide after planting before extensive stem damagehas occurredCutworm. Larvae girdle soybean seedlings below the cotyledons, reducing plantstand. Larvae may also feed on foliage. As soybeans can withstand substantial standreduction without a reduction in yield, control of cutworms is necessary only whenunusually large populations occur.Mid- to Late-Season PestsThreecornered alfalfa hopper. Petiole girdling by adults and nymphs during theblooming and pod-filling stages can reduce yields.Foliage feeding pests. Various caterpillars (including armyworms and beetarmyworms), beetles and grasshoppers feed on soybean foliage. Because all causedefoliation, they are grouped together for damage estimation purposes. These pests canoccur throughout the year, but are most significant from blooming to pod fill whendefoliation can cause yield reductions (see Plant damage, p. 4). Infestations may developvery rapidly and completely defoliate soybean fields. Controlling these pests iscomplicated when several species are involved. Insecticide applied early in the seasonmay cause resurgent populations, making it necessary to treat again (particularly whengrowing conventional varieties, groups VI-IX).Velvetbean caterpillars, green cloverworms, soybean loopers, and cabbage loopers arethe most common and severe defoliators of Texas soybeans. Velvetbean caterpillar mothsmigrate into Texas each year in large numbers, and caterpillar populations can build uprapidly. The larvae are green to brown with stripes along their sides, and have four pairsof abdominal prolegs. Although they are relatively easy to control with insecticides,populations often go undetected until significant damage has occurred. Greencloverworms have three pairs of abdominal prolegs and often require control in the UpperGulf Coast area. Loopers are green caterpillars with two pairs of abdominal prolegs and asingle pair of prolegs at the end of the body; they are sometimes marked with black. Thesoybean looper occasionally becomes abundant earlier in the season than other loopers,and populations are often composed of all sizes. It is not easy to see the differencesbetween looper species, except at the pupal stage. Soybean loopers pupate in silk-like
  • 21. cocoons attached to the undersides of leaves. The pupae are white, cream or pale green incolor. Cabbage looper pupae are brown and pupation occurs at the soil surface.Late-Season and Pod-Filling PestsArmyworm. All three armyworm species feed on all growth stages of the soybeanplant. Army-worms feed mainly on leaves, but also on pods.Stink bugs. The southern green stink bug and brown stink bug are the most commonspecies along the Gulf Coast of Texas, although occasionally other species such as thegreen stink bug are found. Adult stink bugs usually move into fields when soybeansbegin to flower. Both adults and nymphs feed by inserting their mouthparts into the beansinside the pods. They also feed on stems, foliage and blooms. Pod feeding may reduceyield and quality of the soybeans, delay maturity (green bean effect), and increase theincidence of yeast spot seedling disease. Large numbers of nymphs can develop duringthe pod filling period. Because adult females deposit eggs in clusters, nymphs areextremely aggregated. Accurate sampling methods (such as the sweep net methoddescribed earlier) are required to estimate average field populations.Corn earworm. This pest is also known as the cotton bollworm and soybeanpodworm. Female moths lay eggs on the terminal leaves of soybean plants. Larvae feedfor a few days and then move down the plant to feed on developing soybeans.Occasionally, corn earworms are detected during vegetative growth stages. Largepopulations during the pod-filling stage can reduce yield. Infestations are most commonwhere alternate hosts such as corn, sorghum and cotton are grown nearby.Soybean stem borer. These long-horned beetles are occasional pests of soybeans inthe Texas High Plains. Adults are 3/8 inch long, charcoal gray beetles with longantennae. The larvae are cream-colored, legless grubs. Larvae tunnel soybean stems inJuly and August, eventually girdling plants at the base. Plants may lodge and becomedifficult to harvest. Peak girdling activity occurs during September and October.Soybeans should be harvested as soon as possible to minimize losses to the stem borer.Occasional PestsOccasional early-season defoliators include cutworms, garden webworms, southerncorn rootworm, and banded cucumber beetles Their feeding rarely becomes seriousenough to warrant treatment. Several grasshopper species occasionally move into themargins of fields bordered by weedy areas, and at times they require spot treatments.Recently, large numbers of the bean leaf beetle were found in northeast Texas.Populations generally peak in the summer and early fall. Blister beetle larvae areconsidered beneficial because they destroy grasshopper eggs; however, the adult beetlesdefoliate soybeans by feeding on leaves, blooms, tender stems, and young pods. Otherpests such as thrips, whiteflies and spider mites can damage foliage but rarely requiretreatment.
  • 22. Biological ControlThe term “biological control” refers to the suppression of pests by their naturalenemies. Biological control tactics include the conservation, augmentation andimportation of natural enemies. Conservation is the preservation of natural enemies thatare already present. The best way to conserve natural enemies is to avoid usinginsecticides unnecessarily. Augmentation is the mass culturing and periodic release of anatural enemy. Many species of beneficial insects are sold for pest control in soybeans.However, the effectiveness of augmentation in soybeans is unknown and the TexasAgricultural Extension Service cannot provide guidelines for using this method.Importation is the introduction of non-native natural enemies. This method has beeneffective when an exotic pest has entered Texas without the natural enemies that helpcontrol the pest in its native country.Natural enemies of insects that attack soybeans include spiders, lacewings, ladybeetles, ground beetles, rove beetles, syrphid flies, flower flies, hover flies, true bugs(including minute pirate bugs, big-eyed bugs, assassin bugs and damsel bugs), predatorymites, and even fire ants. However, many important natural enemies are rarely seen, suchas parasitic wasps and flies, nematodes, and pathogenic bacteria and fungi.Generally, pesticides kill natural enemies as well as target pests. Once natural enemieshave been destroyed, there is no natural (biological) proteciton against insect pests untilnatural enemy populations recover. This can cause outbreaks of secondary pests or rapidresurgence of pests that were initially suppressed by the pesticide treatment. Pest insectsalso can develop resistance to pesticides. Using nonchemical control methods, orpesticides that kill only the target pest, protects natural enemies. Insecticide applicationsshould be avoided unless economically damaging levels of harmful pests are detected.Microbial Insecticides and Insect Growth RegulatorsBacillus thuringiensis (Biobit®, DiPel®, Design®, Agree®and others) is a biologicalinsecticide labeled for control of several foliage-feeding larvae in soybeans. It is notrecommended where heavy populations develop during the pod-filling period. Thisinsecticide will not control defoliating beetles, grasshoppers or pod-feeding stink bugs.Using Bacillus thuringiensis requires a different approach to insect management. It isrelatively slow acting, much more effective on small worms than large ones, andperforms better when applied in large volumes of water per acre (10 to 15 gallons byground application and 5 to 8 gallons by air) to ensure thorough plant coverage.Biological insecticides generally suppress pest species without disrupting beneficialspecies that contribute to natural control. But to be used effectively, there must beregular, careful field monitoring and accurate analysis of the potential for plant damage.Precise application (timing, rate and coverage) is required. Application equipment mustbe clean so that there is no residue of conventional insecticide that may harm beneficialinsects or the biological control organisms being applied.
  • 23. Virus products (Spod-X®LC, Gemstar®LC) are very specific insecticidal viruses. Theydo not persist long in the field so correct timing of applications is important. The productsdo not affect beneficial insects.Diflubenzuron (Dimilin®) is a compound that prevents certain caterpillars fromforming a new exoskeleton (skin) after molting. It is referred to as a “chitin synthesisinhibitor.” If pest populations are extremely large (two to three times higher than thethreshold) and/or other pests are present (stink bugs, other caterpillar species, etc.) lowrates of conventional insecticides may need to be used with diflubenzuron.Pest thresholds for using biological insecticides may be lower than those forconventional chemical insecticides.Insecticide Application MethodsSpray applications are most effective, but they should not be made when wind velocityexceeds 15 miles per hour. Nozzle size and number, ground speed, and pump pressureinfluence the rate of output per acre. Always calibrate the sprayer carefully to ensure thatthe recommended rate is applied. For ground applications, one nozzle per row may bedesirable on larger plants to obtain thorough coverage. For best results with aerialapplications, flag swaths so they meet or overlap. Do not fly higher than 15 feet above theplant canopy to reduce drift and maximize coverage. When making any insecticideapplication, follow label directions. For calibration and safety information refer to B-1648, “Using Pesticides--Private Applicator Manual: General” (Texas AgriculturalExtension Service).Protecting Bees and Other Pollinators from InsecticidesPollination is extremely important in producing many crops such as alfalfa, clover,vetch and cucurbits. Where pollinating insects are required for flower fertilization, thecrop producer, insecticide applicator and beekeeper should cooperate closely to minimizebee losses. The following guidelines will reduce bee losses:1. Apply insecticides, if practical, before bees are moved into fields or adjacentcrops for pollination. When bees are in the vicinity, apply insecticides in lateevening or early morning when bees are not foraging. Evening applications afterbees have left the field are less hazardous than early morning applications.2. Use the insecticide least toxic to bees that will be effective against target pests.3. Do not spray any insecticide directly on bee colonies and prevent insecticide drift.Bees often cluster on the fronts of their hives on hot evenings. Pesticide drift ordirect spray at this time generally kills many bees.Policy for Making Chemical Control Suggestions
  • 24. The information and suggestions in this publication reflect currently availablemanagement options. Our management suggestions are a product of research and arebelieved to be reliable. However, it is impossible to eliminate all risk. Conditions orcircumstances which are unforeseen or unexpected may result in less than satisfactoryresults even when these suggestions are used. The Texas Agricultural Extension Servicewill not assume responsibility for risks.Suggested pesticides must be registered and labeled for use by the EnvironmentalProtection Agency and the Texas Department of Agriculture. The status of pesticide labelclearances 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 livestock andcrops, as well as for problems that arise from drift or movement of pesticides to theproperty of others. Always carefully read and follow the instructions on the product label.This publication is based on a previous publication by Bastiaan M. Drees and Michael O.Way. The authors are grateful for the assistance of John A. Jackman, Bastiaan M. Drees,Roy Parker and Noel Troxclair.Illustrations on page 5 are by James A. Kalisch and John Kalish. They are fromHandbook of Soybean Insect Pests (1994) published by the Entomological Society ofAmerica, and are reprinted with permission.Soybean Insect Control Suggestions
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  • 35. Soybean Insect Control Suggestions (continued)
  • 36. 1Mexican bean beetle, Japanese beetle, thrips, lygus bug, seedcorn maggot, white grub, wireworm, aphid,leafhopper, cucumber beetle, alfalfa caterpillar, woolly bear caterpillar, painted lady (thistle caterpillar),garden webworm, silver-spotted skipper and two-spotted spider mite are not included in this guide, as theyhave not been found to be pests of Texas soybeans. The Mexican bean beetle and Japanese beetle have notbeen found in sufficient numbers to affect soybean production in Texas.2Often a complex of caterpillar defoliators, including loopers, velvetbean caterpillar and green cloverworm,attack soybeans. Because damage by these species is similar and additive, use the same economic thresholdfor the insect complex. Treat when defoliation by this complex exceeds 40 percent prebloom, 20 percentduring bloom and pod fill, and 35 percent from pod fill to harvest.
  • 37. 3To convert lbs./acre to kg/hectare use the formula: lbs./acre = kg/hectare0.8924An “X” indicates that restrictions on livestock grazing or feeding are not mentioned on the product label.RestrictionsRefer to product labels for endangered species restrictions.Carbaryl--Do not apply a combination of carbaryl and 2,4 DB herbicides to soybeans.Use lower rates for light to moderate populations and smaller instars and to providemaximum survival of beneficial insects and spiders. Use higher rates for heavypopulations and larger instars. For grasshopper control, use the lower rate for nymphs onsmall plants or sparse vegetation in wasteland, rangeland, ditchbanks, rights-of-way,pastures, hedgerows and roadsides. Use the higher (1.5 lbs. AI/acre) rate for adultgrasshoppers or applications to dense vegetation. Also labeled for cucumber beetles,alfalfa caterpillar, leafhoppers, thrips, webworms and painted ladies (thistle caterpillars)Chlorpyrifos--Apply as broadcast spray using either aerial or ground equipment.Reapply as necessary to maintain control. On determinate soybeans, do not make morethan one application after pod set. Also labeled for spider mite control (0.25 to 0.5 lb.AI/acre). When mites and eggs are in large numbers, apply a second spray 3 to 5 daysafter initial treatment to control newly hatched nymphs. Lorsban may also be appliedthrough sprinkler irrigation systems. Do not apply more than 3 lbs. AI chlorpyrifos peracre per season, nor apply the last two treatments closer than 14 days apart.Diflubenzuron--See discussion in "Biological insecticides." For aerial application, applywhen larvae are small (less than 1/2 inch). Apply in sufficient (1 to 3 gals. per acre) waterto achieve uniform coverage of foliage. For ground application, apply recommended ratein 9 to 35 gals. of water per acre to achieve uniform coverage. Do not make more thantwo applications per season. From 3 to 5 days may be required before populations arereduced. Do not rotate crops other than soybeans or cotton until 6 months following lastapplication. Do not apply to lakes, streams, ponds or other bodies of water.Es-fenvalerate--Do not feed or graze livestock on treated plants. Do not exceed 0.2 lb.AI per acre per season. When applying in nonvoliatile vegetable oils use a total sprayvolume of 1 or more quarts.Methomyl--Also labeled for thrips. For aerial application of Lannate®LV as a low-volume spray, ensure that equipment is capable of delivering small spray droplets forthorough coverage, and that equipment is adjusted to distribute spray uniformly over thespray swath. Apply when wind, temperature and humidity will allow spray to bedelivered to the target area. Make sure local regulations do not prohibit low-volume aerialsprays. Apply in a minimum total spray volume of 0.53 gal. per acre. Water or once-
  • 38. refined vegetable oil may be used as the spray carrier. Continue to apply at 5- to 7-dayintervals or as needed to maintain control.Methyl parathion--Do not apply more than twice per growing season. Productscontaining methyl parathion are also registered for use on thrips, garden webworms, two-spotted spider mites, leafhoppers, and silver-spotted skippers.Permethrin--Apply by air or ground. Do not apply more than 0.4 lbs. AI per acre perseason. Apply Pounce®25 WP in a minimum of 1 gal. finished spray per acre by air or 5gallons with ground equipment. When applying Pounce®3.2EC in nonvolatile vegetableoil, apply in a minimum of 1 qt. total volume per acre using equipment calibrated to giveadequate coverage. When applying in water by aircraft, 1 qt. of oil may be substituted for1 qt. water per gallon of finished spray.Thiodicarb--Apply in a minimum finished spray volume of 2 gals. per acre by air or 5gals. per acre by ground. Use lower rates for low to moderate populations and maximumprotection of beneficials. Refer to product label for special instructions for cutwormapplications.Tralomethrin--For aerial applications, use a minimum of 1 gal. of water per acre or 1 qt.of at least once-refined crop oil per acre. For ground applications, use a minimum of 5gals. of water per acre for thorough coverage of the foliage.Additional Insecticide Products Registered For Use On Soybeans (Note: Theinformation below is presented for completeness of available product information only.This listing does not constitute a recommendation for use of these products in Texassoybean production.)Carbofuran (Furadan®4F) -- Labeled for grasshopper control as a foliar applicationusing 1/4 to 1/2 pt. in 20 or more gals. of water per acre. Do not apply within 21 days ofharvest and do not graze or feed foliar-treated forage to livestock or cut for silage or hay.Dichloropropene (Telone®II, Telone®C-17) -- Labeled for wireworms.Ethyl phosphosphorodithioate (Di-Syston®15%) -- Labeled for aphids, leafhoppers,mites, thrips (except flower thrips), and Mexican bean beetle. Place granules in a 4-inchband over the seed furrow behind the planter shoe and in front of the press wheel, or in aband on each side of the seed furrow at planting time. 6.7 lbs./acre. Allow at least 75 daysbetween application and harvest for forage or hay.Malathion (Malathion ULV Concentrate) -- Labeled for grasshopper and greencloverworm control at a rate of 8 fl. oz. per acre, undiluted. Do not harvest or graze for 7days following application.Metaldehyde (Metaldehyde 7.5G) -- Labeled for slugs and snails.
  • 39. Methoxychlor (Methoxychlor 4L) -- Labeled for velvetbean caterpillar, blister beetles,garden webworm, leafhopper and fall armyworm at a rate of 1 to 3 qts. per acre, with apre-harvest interval of 7 days.Neem oil (Trilogy®) -- Labeled as a broad-spectrum miticide/insecticide/fungicide.Permethrin plus methyl parathion (Pounce®Plus Methyl Parathion 2-5EC) -- Labeledfor control of cabbage looper, corn earworm, soybean looper, velvetbean caterpillar, beanleaf beetle, alfalfa looper and garden webworm at 6.4 to 12.8 fl. oz. per acre and for stinkbug and threecornered alfalfa hopper at a rate of 12.8 fl. oz. per acre. This product isconvenient when a complex of pests occurs that does not respond to the ingredients inthis product applied separately. Application may be made with air or ground equipment.Use a minimum of 1 gal. of water per acre with aircraft or 5 gals. of water per acre withground equipment. Do not make more than two applications per season. Do not applywithin 40 days of harvest. Do not feed or graze soybean forage. Do not plant rotationalcrops within 60 days of last application.Phorate (Thimet®15G and 20G) -- Labeled for the early season control of thrips, mitesand other insects as an at-plant application at a rate of 12 oz. (Thimet 15G) and 9.0 oz.(Thimet 20G) per 1000 feet of row.N-methyl carbamate (Slam®) -- Labeled for control of diabroticine beetle adults. Apply0.5-0.75 lb/acre. 0 days pre-harvest interval.Conversion table: Pounds of active ingredients (AI) per acre to amount offormulation per acre. For additional conversions use these formulas:lb. AI per acre ÷ lb. formulation per gal. = gal. formulation per acre; lb. AI formulationper acre ÷ % AI formulation per acre ÷ 100 = lb. formulation per acreNote: 1 gal. = 4 qts. = 8 pts. = 128 fl. oz.and formulation Pounds of active ingredients (AI) per acre converted to amount actual product per acre0S 0.5 lb. AI. = 0.63 lb./acre; 1.0 lb. AI = 1.25 lbs./acre; 1.5 lbs. AI = 1.87 lbs./acre; 2.0 lbs. AI = 2.5 lbs./acr0WP 0.5 lb. AI. = 1.0 lb./acre; 1.0 lb. AI = 2.0 lbs./acre; 1.5 lbs. AI = 3.0 lbs./acre; 2.0 lbs. AI = 4.0 lbs./acreLR Plus 0.5 lb. AI. = 0.5 qt./acre; 1.0 lb. AI = 1.0 qt./acre; 1.5 lbs. AI = 1.5 qts./acre; 2.0 lbs. AI = 2.0 qts./acres4E 0.25 lb. AI = 0.5 pt./acre; 0.5 lb. AI = 1.0 pt./acre; 0.75 lb. AI = 1.5 pts./acre; 1.0 lb. AI = 2.0 pts./acre15G 5.7 lbs. AI = 38.0 lbs./acre
  • 40. on25W 0.03125 lb. AI = 2.0 oz./acre; 0.0625 lb. AI = 4.0 oz./acreate.9EC 0.0125-0.025 lb. AI = 0.85-1.7 fl. oz./acre; 0.025 0.05 lb. AI = 1.7-3.4 fl. oz./acreLV 0.13 to 0.25 lb. AI = 0.43 to 0.83 pts./acre; 0.38 lb. AI = 1.27 pts./acre; 0.5 lb. AI = 1.67 pts./acre; 1.0 lb.thionarathion 4E andEC 0.25 lb. AI = 0.5 pt./acre; 0.38 lb. AI = 0.76 pt./acre; 0.5 lb. AI = 1.0 pt./acre; 1.0 lb. AI = 2.0 pts./acrearathion 7.5 0.25 lb. AI = 0.27 pt./acre; 0.38 lb. AI = 0.41 pt./acre; 0.5 lb. AI = 0.53 pt./acre; 1.0 lb. AI = 1.1 pts./acreM 0.25 lb. AI = 1.0 pt./acre; 0.5 lb. AI = 2.0 pts./acre; 0.75 lb. AI = 3.0 pts./acre; 1.0 lb. AI = 4.0 pts./acre25W ande®25WP 0.05 lb. AI = 3.2 oz./acre; 0.1 lb. AI = 6.4 oz./acre; 0.2 lb. AI = 12.8 oz./acre25W and3.2EC 0.05 lb. AI = 2.0 fl. oz./acre; 0.1 lb. AI = 4.0 fl. oz./acre; 0.2 lb. AI = 8.0 fl. oz./acre3.20.25-0.4 lb. AI = 10.0-16.0 fl. oz./acre; 0.45-0.75 lb. AI = 18.0-30.0 fl. oz./acre; 0.5-0.75 lb. AI = 20.0-30oz./acren0.014-0.017 lb. AI = 6.0-7.0 fl. oz./acre; 0.015-0.019 lb. AI = 6.4-8.0 fl. oz./acre-traTM0.012-0.016 lb. AI = 1.73-2.33 fl. oz./acre; 0.016-0.024 lb. AI = 2.33-3.33 fl. oz./acre
  • 41. Southern green stinkbug Beet Armyworm Silver spotted skipperSoybean stem borer Saltmarsh catarpillar Banded cucumber beetleSoybean thrips Bean leaf beetle Blister beetlePhotographs provided by Bastiaan Drees, Michael O. Way and Noel Troxclair.Geeen clover worm Velvet bean caterpillarThree-cornered alfalfahopper
  • 42. Corn earworm Fall armyworm Black cutwormThe information given herein is for educational purposes only. Reference to commercialproducts or trade names is made with the understanding that no discrimination is intendedand no endorsement by the Cooperative Extension Service is implied.Produced by Agricultural Communications, The Texas A&M UniversitySystemExtension publications can be found on the Web at:http://agpublications.tamu.eduEducational programs of the Texas Agricultural Extension Service are open to all peoplewithout regard to race, color, sex, disability, religion, age or national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and HomeEconomics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, incooperation with the United States Department of Agriculture. Chester P. Fehlis, DeputyDirector, Texas Agricultural Extension Service, The Texas A&M University System.5M, Revision 6-99AGR8-4