NC State Extension Publications

 

Within the geographic range that soybeans are grown in North Carolina, the likelihood of economic loss from insects is highly variable. Pest insect abundance and species diversity in soybeans generally increases across the state in a southerly and easterly direction. For example, soybeans in a mid-coastal county (e.g., Carteret county) will generally experience economic infestations from several different pest species, whereas insect-associated soybean loss in the interior of the state (e.g., Franklin county) is typically infrequent and limited to corn earworm.

Soybeans harbor many species of insects. Several have the potential to be pests under high populations, but most are either beneficial predators or parasites or perform no function of direct interest to the soybean producer. Those insects that do feed upon the plant have traditionally been classified as either foliage feeders or pod feeders, although a few may feed on both plant parts. Most of these plant-feeding insects have chewing mouthparts (e.g., beetles and caterpillars), but some pierce the plant and suck juices (e.g., leafhoppers, kudzu bugs, and stink bugs). A few species feed on the underground stems, roots, and nodules. Approximately 20 different plant-feeding insects are easily found in soybean fields, but their individual or collective abundance or damage usually does not exceed the economic threshold.

Insect Management Practices

The soybean plant has an almost unbelievable capacity to tolerate insect attack when grown under favorable conditions. Low to moderate levels of root or nodule feeding and flower or pod feeding will have no effect on yield. Recent research has demonstrated that relatively high levels of defoliation, especially during the early vegetative growth stages will also have little to no effect on yield. In contrast, another field crop, cotton, and most fruit and vegetables be can be adversely affected by a comparatively low number of insects. An abundance of insect pests in soybean, in contrast, does not mean that yield loss has begun. Research-based thresholds describe the level of pests or defoliation required to produce loss and should be used when deciding if insecticide management actions are necessary. Thresholds allow the soybean producer to attain the highest possible yield at the least cost. It is easy to unwisely increase the cost of insect control by not recognizing the plant’s potential to tolerate some insect damage. On the other hand, it is equally easy to underestimate the potential of insect pests to rob soybean yield by attempting to minimize inputs.

Managing pests in any crop involves a consideration of agronomic, economic, and biological factors. Soybean, like all field crops, is a low value crop that cannot support high cost pest management techniques. Therefore, low cost practices to avoid the build-up of insect pests and enhance the soybean crop’s ability to tolerate insect injury should be employed. These avoidance practices include several cultural techniques that: (1) help ensure a healthy, competitive, and compensating crop; (2) avoid infestations of pests by site selection; (3) seek to make the crop unattractive or unsuitable for some pests; and (4) preserve biological control organisms for pest suppression. Avoidance techniques can greatly reduce insect damage to soybeans but cannot always be used in full force or may not work as well as hoped. In such cases, damaging infestations may occur, and remedial techniques, such as insecticides, should be employed based on scouting and treatment thresholds.

Soybean Insect Scouting

Thresholds. When scouting, some level of insects and their damage will always be observed. However, most situations will not result in yield loss because the insect numbers present are too low to produce injury beyond the plant’s compensation ability. As a result, thresholds play a critical part in any integrated pest management program, because they help producers balance the need for a management intervention (in this case, an insecticide application). Some of the thresholds presented here are economic thresholds, in which the density of a pest has reached a point at which a management intervention is economically justified. Other thresholds, such as the foliage feeding thresholds, are points at which management efforts can safely be made without experiencing yield loss. An economic threshold should not be confused with the economic injury level. An economic injury level is the lowest population density of a pest that will cause economic damage. Treatment when economic injury level is reached may result in the highest yields, but may not necessarily be the most cost-effective. Treatment at the economic threshold is the most cost-effective management approach and may or may not result in the highest yields.

Soybean insect pests. A wide variety of insects may be found in a North Carolina soybean field at any given time of the season. Some of these insects may be pests that could reduce soybean yield, while others may be beneficial insects that prey on pests. Therefore, correct identification is the most important step that a soybean producer can take for successful pest management.

Pest Avoidance through Crop Management

Differences caused by variety selection, planting date, cultural techniques, site, and season render soybean attractiveness to insect pests highly variable. In other words, all soybean fields, although planted to a single crop, are not alike as far as attracting and building-up pest insects is concerned. If soybean producers recognize these differences, they can manage the crop to minimize pest abundance. When this is not possible, they can predict which fields are attractive and may need more attention to prevent yield loss. Also, pest insects in soybean fields are greatly reduced by beneficial insects. If these predators and parasites are not adversely affected by insecticide use, they will provide the producer with insect control. Several tactics are known to minimize soybean pest abundance:

Site selection. Several insect and pathogen pests build up if soybeans are not rotated; therefore, rotation helps insure reduced pest levels and improved crop health. Sites that have limiting pest, physical, or soil chemical problems should be avoided if these problems cannot be corrected.

Early planting. Planting before mid-May usually ensures that few late season caterpillars will develop in the field; however, some early planted fields may be more attractive to bean leaf beetle, thrips, and kudzu bugs (minor pests) and, occasionally, stink bugs.

Fertility and pH maintenance. Thin and short stands often have more corn earworms, and poor growth reduces the plant’s ability to compensate for damage. Reducing plant stress from low pH, poor fertility, or inadequate moisture will enable plants to tolerate insect feeding.

Variety selection. If planted early, maturity Group IV, V, and earlier maturing varieties will bloom and harden-off before the corn earworm moth flight, making them unsuitable for infestation. Also, early maturity can greatly reduce soybean looper, velvetbean caterpillar, and late stink bug infestations; in rare situations stink bugs can be trap cropped by early maturity fields.

Narrow rows. A complete canopy allows a higher level of biological control by insect predators, parasites, and diseases. Also, narrow-row soybeans are less attractive to egg laying corn earworm moths.

Avoiding unwarranted insecticide use. Both foliar sprays used during the season and insecticide seed treatments used during planting may reduce the build-up of beneficial insects and lead to more severe later season caterpillar infestations. Early season insect pests rarely require insecticide applications and, if insecticides are used, they may produce more negative consequences than benefits by removing predators and parasites. Also, published research from North Carolina shows that, while insecticide seed treatments can eliminate supposed insect pests such as thrips, they do not provide a yield benefit. In areas that have soybean looper and velvetbean caterpillar, spraying for corn earworm or stink bug may lead to high infestation by these later season pests. Therefore, avoiding unwarranted corn earworm treatments (i.e., automatic insecticide sprays at flowering) will tend to reduce other late season caterpillar numbers. Also, insecticide intended for corn earworm, but applied too early, can cause a severe corn earworm infestation later.

There are many other examples of practices that influence insect pest abundance. For example, kudzu bugs are less attracted to fields that are conventionally tilled, and lesser cornstalk borers are more problematic behind double-cropped fields that have been burned. The use of cover crops prior to soybean plantings can also influence pest abundance in the following soybean crop.

Insecticide Selection and Application

If insecticides are applied using ground equipment, a minimum volume of 6 gallons per acre applied through hollow cone nozzles should be used; pressures of about 60 to 70 psi or higher are preferred. Ground sprayers—high clearance or tractor mounted—can be operated in wide row soybeans (above 30 in.) without much equipment damage to the crop. Equipment damage potential is highly influenced by soybean plant height and erectness and the sprayer boom width.

Damage from ground sprayers in narrow row soybeans (less than 30 in.) can be significant. Yield loss can be over four bushels per acre for both the high clearance and tractor-mounted sprayers (Table 9-1), and can be even greater in higher-yield potential situations. Furthermore, yield loss potential is even greater if soybean plants are lodged and tangled. Although damage from ground sprayers may be undesirable, such equipment should be used to avoid injury in drift-sensitive areas and when air application equipment is not immediately available.

In the table below, the yield loss from sprayers is predicted in 35 bu/A narrow row (7 in.) soybean after insecticide spray simulation with a high-clearance or tractor mounted group sprayer. Results are an average of three tests (Heim, C.D., Van Duyn, J.W., and Bradley, J.R., Jr.)


Table 9-1. Yield reduction in bushels per acre.

Spray Boom Width
(ft)

% Area in
Traffic Lane

High Clearance
(bu/A)

Tractor
(bu/A)

12

75

4.73

5.51

18

50

3.15

3.68

24

38

2.39

2.79

30

30

1.89

2.21

36

25

1.58

1.84

42

21

1.32

1.53


Aircraft are often used to apply insecticide to soybean. Airplane and helicopter application volume is typically one to three gallons per acre. If approximately 1 gallon per acre is used, the carrier often contains water plus an emulsified vegetable oil to reduce evaporation. All of these techniques may perform well if field size and shape, obstacles (e.g., power lines), and weather conditions are satisfactory. Aircraft spraying may be undesirable, however, if fields are small or close to houses or businesses, have significant road frontage, or are in areas adjacent to waterways. Aircraft can be especially important in periods of corn earworm outbreak, when significant acreage must be treated quickly, or when wet field conditions make ground spraying impossible.


Table 9-2. Insect control on soybeans.
Insect
Insecticide and Formulation
per Acre Acres/gal. (lb) Preharvest Interval (PHI) (Days) Precautions and Remarks
Amount of Formulation Active (lb)
Bean Leaf Beetle
acephate, MOA 1B (Orthene) 97 S 0.75 to 1 lb 0.75 to 1 1.25 to 1 14 Treat when defoliation reaches threshold levels or buildup is obvious. Threshold is 30% prebloom defoliation or 15% defoliation 2 weeks prior to bloom through podfill. Pod skinning by this insect can be a concern in soybeans grown for seed. Selected pyrethroids will suppress bean leaf beetle. Tolerance can quickly develop if chemistries are not rotated. In the premixed products listed, the effective chemistries are in MOA’s 3 and 1B.
acetamiprid, MOA 4A + bifenthrin, MOA 3 (Justice) 1.8 EC 5 fl oz See label 25.6 30
beta-cyfluthrin, MOA 3 (Baythroid XL) 1.0 EC 2.8 fl oz 0.022 45.7 45
bifenthrin, MOA 3(Brigade, Discipline, Sniper, and others) 2 EC 4 to 6.4 fl oz 0.062 to 0.10 32 to 20 30
chlorantraniliprole, MOA 28 + lambda-cyhalothrin, MOA 3 (Besiege) 1.25 SC 5 to 8 fl oz See label 25.6 to 16 21
chlorpyrifos, MOA 1B +gamma-cyhalothrin, MOA 3(Cobalt Advanced) 2.63 EC 19 to 24 fl oz See label 6.7 to 5.3 30
chlorpyrifos, MOA 1B (Lorsban) 4 E 1 to 2 pt 0.5 to 1 8 to 4 14
cyfluthrin, MOA 3 (Tombstone) 2 E 1.6 to 2.8 fl oz 0.025 to 0.04 80 to 45.7 45
diflubenzuron, MOA 15 + lambda-cyhalothrin, MOA 3 (DoubleTake) 3 SC 4 fl oz See label 32 30
imidacloprid, MOA 4A + cyfluthrin, MOA 3 (Leverage 360) 3.0 SE 2.8 fl oz See label 45.7 45
lambda-cyhalothrin, MOA 3(Warrior, Lambda-cyhalothrin, Silencer) 1.0 EC(Karate Z and Warrior II) 2.08 CS 1.92 to 3.2 fl oz0.96 to 1.6 fl oz 0.015 to 0.0250.015 to 0.025 66.7 to 40133.3 to 80 3030
lambda-cyhalothrin, MOA 3 + thiamethoxam, MOA 4A (Endigo ZC) 2.06 SE 4 to 4.5 fl oz See label 32 to 28.4 30
Beet Armyworm
chlorantraniliprole, MOA 28 (Prevathon) 0.43 SC 14 to 20 fl oz 0.047 to 0.067 9.1 to 64 1 Ground application only for larger caterpillars. Control of large armyworms is difficult. Chlorantraniliprole, indoxacarb, methoxyfenozide, spinetoram, and spinosad are the superior products.
chlorantraniliprole, MOA 28 + lambda-cyhalothrin, MOA 3 (Besiege) 1.25 SC 9 fl oz 0.04 + 0.02 14.2 21
indoxacarb, MOA 22 (Steward) 1.25 EC 5.6 to 11.3 fl oz 0.06 to 0.11 22.9 to 11.3 21
methomyl, MOA 1A(Lannate) 2.4 LV(Lannate) 90 SP 1.5 pt0.5 lb 0.450.45 5.32 1414
methoxyfenozide, MOA 18A (Intrepid) 2 F 4 to 8 fl oz 0.06 to 0.12 32 to 16 14 (grain)7 (hay)
methoxyfenozide, MOA 18A + spinetoram,MOA 5 (Intrepid Edge) 3F 4.0 to 6.4 oz See label 32 to 20 28
spinosad, MOA 5 (Blackhawk) 4 SC 1.7 to 2.2 fl oz 0.04 to 0.05 75.3 to 58.2 28
Corn Earworm
beta-cyfluthrin, MOA 3 (Baythroid XL) 1.0 EC 1.6 to 2.8 fl oz 0.0125 to 0.022 80 to 45.7 45 Treat when earworm numbers exceed threshold as determined by scouting. Be sure worms are present and 38 to 12 inch in size when treatment is applied. Use low rates for light infestations. Use higher rates by air. Some resistance to pyrethroids has been found in North Carolina corn earworm populations. Distinguishing between corn earworm and tobacco budworm is important as pyrethroids provide poor control of tobacco budworm. A pyrethroid combined with 0.5 pound/acre acephate will improve control in situations where tobacco budworm is present or resistance of corn earworm to pyrethroids is present. Effective products with a pyrethroid-alternative chemistry include chlorantraniliprole, indoxacarb, spinetoram, and spinosad. Use the online threshold calculator. At $10.00 per bushel, the plant compensates due to the low caterpillar levels needed to reach threshold at $10.00 and above.
chlorantraniliprole, MOA 28 (Prevathon) 0.43 SC 14 to 20 fl oz 0.047 to 0.067 9.1 to 6.4 1
chlorantraniliprole, MOA 28 + lambda-cyhalothrin, MOA 3 (Besiege) 1.25 SC 6 to 9 fl oz See label 21.3 to 14.2 21
chlorpyrifos, MOA 1B (Lorsban) 4 EC 1.5 to 2 pt 0.75 to 1 5.3 to 4 14
cyfluthrin, MOA 3 (Tombstone) 2 E 1.6 to 2.8 fl oz 0.025 to 0.04 80 to 45.7 45
esfenvalerate, MOA 3 (Asana XL) 0.66 EC 5.8 to 9.6 fl oz 0.03 to 0.05 22.1 to 13.3 21
chlorpyrifos, MOA 1B +gamma-cyhalothrin, MOA 3(Cobalt Advanced) 2.63 EC 16 to 38 fl oz See label 8 to 3.4 30
gamma-cyhalothrin, MOA 3 (Declare) 1.25 EC 1.54 fl oz 0.015 83.1 21
imidacloprid, MOA 4A +beta-cyfluthrin, MOA 3 (Leverage 360) 3.0 SE 2.8 fl oz 0.04 + 0.02 45.7 15
indoxacarb, MOA 22 (Steward) 1.25 EC 5.6 to 11.3 fl oz 0.06 to 0.11 22.9 to 11.3 21
lambda-cyhalothrin, MOA 3(Warrior, Lambda-cyhalothrin, Silencer) 1.0 EC(Karate Z and Warrior II) 2.08 CS 1.92 to 3.2 fl oz0.96 to 1.6 fl oz 0.015 to 0.0250.015 to 0.025 66.7 to 40133.3 to 80 3030
lambda-cyhalothrin, MOA 3 + thiamethoxam, MOA 4A (Endigo ZC) 2.06 SE 3.5 to 4 fl oz See label 36.6 to 32 30
methoxyfenozide, MOA 18A + spinetoram, MOA 5 (Intrepid Edge) 3F 4.0 to 6.4 oz See label 32 to 20 28
spinosad, MOA 5 (Blackhawk) 4 SC 1.7 to 2.2 fl oz 0.04 to 0.05 75.3 to 58.2 28
zeta-cypermethrin, MOA 3(Mustang Max) 0.8 EC 2.8 to 4 fl oz 0.0175 to 0.025 45.7 to 32 21
zeta-cypermethrin, MOA 3 + bifenthrin, MOA 3 (Hero) 1.24 EC 10.3 fl oz 0.033 + 0.066 12.4 30
Grasshopper
acephate, MOA 1B (Orthene 97) 0.25 to 0.5 lb 0.25 to 0.5 4 to 2 14 Apply by air or ground uniformly over foliage as a broadcast treatment. Early morning treatment is preferred. Use higher rates for heavy infestations. Diflubenzuron is not effective to control adult grasshoppers. See label for additional instructions and suggestions.
chlorpyrifos, MOA 1B +gamma-cyhalothrin, MOA 3(Cobalt Advanced) 2.63 EC 10 to 13 fl oz See label 12.8 to 9.8 30
chlorpyrifos, MOA 1B (Lorsban) 4 E 1 to 2 pt 0.5 to 1 8 59 4 14
diflubenzuron, MOA 15(Dimilin) 2L, 25W 2 fl oz0.25 lb. 0.060.06 648 21
Green Cloverworm
Bacillus thuringiensis, MOA 11B2 (Various) 0 Treat when defoliation reaches threshold. This insect is seldom an economic pest. See label of specific B.t. products. Thresholds are listed under bean leaf beetle. Pyrethroid insecticides are labeled for green cloverworm control at, or below, the rates shown under “Corn Earworm.”
beta-cyfluthrin, MOA 3 (Baythroid XL) 1.0 EC 1.6 to 2.8 fl oz 0.0125 to 0.022 80 to 45.7 45
chlorantraniliprole, MOA 28 (Prevathon) 0.43 SC 14 to 20 fl oz 0.047 to 0.067 9.1 to 6.4 1
chlorantraniliprole, MOA 28 + lambda-cyhalothrin, MOA 3 (Besiege) 1.25 SC 5 to 8 fl oz See label 25.6 to 16 21
cyfluthrin, MOA 3 (Tombstone) 2E 1.6 to 2.8 fl oz 0.025 to 0.04 80 to 45.7 45
esfenvalerate, MOA 3 (Asana XL) 0.66 EC 5.8 to 9.6 fl oz 0.03 to 0.05 22.1 to 13.3 21
gamma-cyhalothrin, MOA 3 (Declare) 1.25 EC 1.54 fl oz 0.015 83.1 21
indoxacarb, MOA 22 (Steward) 1.25 EC 8 to 11.3 fl oz 0.08 to 0.11 16 to 11.3 21
lambda-cyhalothrin, MOA 3(Warrior, Lambda-cyhalothrin, Silencer) 1.0 EC(Karate Z and Warrior II) 2.08 CS 1.92 to 3.2 fl oz0.96 to 1.6 fl oz 0.015 to 0.0250.015 to 0.025 66.7 to 40133.3 to 80 3030
lambda-cyhalothrin, MOA 3 + thiamethoxam, MOA 4A (Endigo ZC) 2.06 SE 3.5 to 4 fl oz See label 36.6 to 32 30
methoxyfenozide, MOA 18A + spinetoram, MOA 5 (Intrepid Edge) 3F 4.0 to 6.4 oz See label 32 to 20 28
spinosad, MOA 5 (Blackhawk) 4 SC 1.1 to 2.2 fl oz 0.025 to 0.05 116.4 to 58.2 28
zeta-cypermethrin, MOA 3(Mustang Maxx) 0.8 EC 2.8 to 4 fl oz 0.0175 to 0.025 45.7 to 32 21
zeta-cypermethrin, MOA 3 + bifenthrin, MOA 3 (Hero) 1.24 EC 10.3 fl oz 0.033 + 0.066 12.4 30
Kudzu Bug
acephate, MOA 1B (Orthene) 97 S 1 lb 1 1 14
bifenthrin, MOA 3(Brigade, Discipline, Sniper, and others) 2 EC 4 to 6.4 fl oz 0.062 to 0.10 32 to 20 30
bifenthrin, MOA 3 + acetamiprid, MOA 4a (Justice) 1.8 EC 5 fl oz See label 25.6 30
bifenthrin, MOA 3 + imidacloprid, MOA 4A(Brigadier) 2 E(Swagger) 1 F 6.1 fl oz12.2 fl oz See labelSee label 2110.5 718
gamma-cyhalothrin, MOA 3 (Declare) 1.25 EC 1.54 fl oz 0.015 83.1 21
lambda-cyhalothrin, MOA 3(Karate, Lambda-cyhalothrin, Silencer) 1.0 EC(Karate Z, Warrior II) 2.08 CS 3.84 fl oz1.92 fl oz 0.030.03 33.366.7 3030
lambda-cyhalothrin, MOA 3 + thiamethoxam, MOA 4A (Endigo ZC) 2.06 SE 3.5 to 4.5 fl oz See label 36.6 to 28.4 30
zeta-cypermethrin, MOA 3(Mustang Maxx) 0.8 EC 4 fl oz 0.025 32 21
zeta-cypermethrin, MOA 3 + bifenthrin, MOA 3 (Hero) 1.24 EC 6.4 to 10.3 fl oz See label 20 to 12.4 30
Soybean Looper
chlorantraniliprole, MOA 28 (Prevathon) 0.43 SC 14 to 20 fl oz 0.047 to 0.067 9.1 to 6.4 1 Treat when thresholds are reached or when buildup is obvious. Threshold is 15% defoliation in soybeans two weeks prior to flowering, but can be increased to 20% during R6 when growing conditions are ideal. Ground application is superior. Resistance is occurring in this species and has been documented in the Blacklands for MOA 3 18A, and 28; insecticides work best on small caterpillars. The most consistent insecticides in Blacklands are those containing MOA 5.
chlorantraniliprole, MOA 28 + lambda-cyhalothrin, MOA 3 (Besiege) 1.25 SC 5 to 9 fl oz See label 25.6 to 14.2 21
chlorpyrifos, MOA 1B +gamma-cyhalothrin, MOA 3(Cobalt Advanced) 2.63 EC 20 to 38 fl oz See label 6.4 to 3.4 30
indoxacarb, MOA 22 (Steward) 1.25 EC 5.6 to 11.3 fl oz 0.06 to 0.11 22.9 to 11.3 21
methoxyfenozide, MOA 18A (Intrepid) 2F 4 to 8 fl oz 0.06 to 0.12 32 to 16 7 (hay)14 (grain)
methoxyfenozide, MOA 18A + spinetoram,MOA 5 (Intrepid Edge) 3F 4.0 to 6.4 oz See label 32 to 20 28
spinetoram, MOA 5 (Radiant) 1 SC 2 to 4 fl oz 0.016 to 0.12 64 to 32 7 (hay)14 (grain)
spinosad, MOA 5 (Blackhawk) 4 SC 1.1 to 2.2 fl oz 0.025 to 0.05 116.4 to 58.2 28
spinosad, MOA 5 + gamma-cyhalothrin, MOA 3 (Consero) 2 to 3 fl oz See label 64 to 42.7 See label
Spider Mite
bifenthrin, MOA 3(Brigade, Discipline, Sniper, and others) 2 EC 5.12 to 6.4 fl oz 0.08 to 0.10 25 to 20 18 Miticides registered on soybean often provide erratic control. Two applications may be needed for high populations. The only true miticidal product listed is extoxazole, which has activity on the immatures.
chlorpyrifos, MOA 1B (Lorsban) 4E 1 to 2 pints 0.5 to 1 8 to 4 28
etoxazole, MOA 11A1 (Zeal) SC 2 to 6 fl oz 0.045 to 0.135 64 to 21
Stink Bug (Brown, Brown Marmorated, Green, and Southern Green)
acephate, MOA 1B (Orthene) 97 S 0.5 to 1 lb 0.5 to 1 2 to 1 14 Treat when bug numbers exceed threshold. Use threshold table. Acephate and the highest rates of pyrethroids are preferred for brown stink bug, with bifenthrin the preferred pyrethroid. Stink bugs are often late-season pests so be aware of the preharvest interval of insecticides. In the premixed products listed, the effective chemistries are in MOAs 3 and 1B.
bifenthrin, MOA 3(Brigade, Discipline, Sniper, and others) 2 EC 2.1 to 6.4 fl oz 0.033 to 0.10 61 to 20 30
chlorpyrifos, MOA 1B +gamma-cyhalothrin, MOA 3(Cobalt Advanced) 2.63 EC 20 to 38 fl oz See label 6.4 to 3.4 30
cyfluthrin, MOA 3 (Tombstone) 2E 1.6 to 2.8 fl oz 0.025 to 0.04 80 to 45.7 45
diflubenzuron, MOA 15 + lambda-cyhalothrin, MOA 3 (DoubleTake) 3 SC 4 fl oz See label 32 30
gamma-cyhalothrin, MOA 3 (Declare) 1.25 EC 1.54 fl oz 0.015 83.1 21
imidacloprid, MOA 4A + cyfluthrin, MOA 3 (Leverage 360) 3.0 SE 2.8 fl oz See label 45.7 45
lambda-cyhalothrin, MOA 3(Warrior, Lambda-cyhalothrin, Silencer) 1.0 EC(Karate Z and Warrior II) 2.08 CS 1.92 to 3.2 fl oz0.96 to 1.6 fl oz 0.015 to 0.0250.015 to 0.025 66.7 to 40133.3 to 80 3030
lambda-cyhalothrin, MOA 3 + thiamethoxam, MOA 4A (Endigo ZC) 2.06 SE 4 to 4.5 fl oz See label 32 to 28.4 30
zeta-cypermethrin, MOA 3(Mustang Maxx) 0.8 EC 4 fl oz 0.025 32 21
zeta-cypermethrin, MOA 3 + bifenthrin, MOA 3 (Hero) 1.24 EC 10.3 fl oz 0.033 + 0.066 12.4 21
Velvetbean Caterpillar
Bacillus thuringiensis, MOA 11B2 (various) 0 See specific labels for use rates.
pyrethroids, MOA 3
chlorantraniliprole, MOA 28 (Prevathon) 0.43 SC 14 to 20 fl oz 0.047 to 0.067 9.1 to 6.4 1
chlorantraniliprole, MOA 28 + lambda-cyhalothrin, MOA 3 (Besiege) 1.25 SC 5 to 9 fl oz See label 25.6 to 14.2 21
diflubenzuron, MOA 15 (Dimilin) 2L 2 to 4 fl oz 0.06 to 0.125 64 to 32 21
methoxyfenozide, MOA 18A (Intrepid) 2F 4 to 8 fl oz 0.06 to 0.12 32 to 16 7 (hay)14 (grain)
methoxyfenozide, MOA 18A + spinetoram,MOA 5 (Intrepid Edge) 3F 4.0 to 6.4 oz See label 32 to 20 28
spinetoram, MOA 5 (Radiant) 1 SC 2 to 4 fl oz 0.016 to 0.12 64 to 32 7 (hay)14 (grain)
spinosad, MOA 5 (Blackhawk) 4 SC 1.1 to 2.2 fl oz 0.025 to 0.05 116.4 to 58.2 28
Grape Colaspis, Blister Beetle, Japanese Beetle, Mexican Bean Beetle, Spotted Cucumber Beetle, Three Cornered Alfalfa Hopper
acephate, MOA 1B (Orthene) 97 S 0.75 to 1 lb 0.75 to 1 1.25 to 1 14 These insects are rarely pests; exercise care in determining if a problem exists. Do not spray Mexican bean beetle when many eggs and pupae are present; wait 4 to 5 days. Thrips have never been demonstrated to reduce soybean yields in North Carolina. Three cornered alfalfa hopper girdle mainstems when plants are below 10 inches tall and petioles when plants are larger. Treatments for three-cornered alfalfa hopper only impact yield when applied to seedling soybeans.
pyrethroids, MOA 3 combinations (see corn earworm above for rates)

Problem Insects

The corn earworm is generally the most important insect pest of North Carolina soybeans, followed by stink bugs. Soybean looper, velvetbean caterpillar, green cloverworm, and bean leaf beetle infrequently occur at high populations and may sometimes reach damaging levels. Soybean looper, stink bugs, and velvetbean caterpillar occur with some regularity in coastal counties below the Albemarle Sound. Other plant-feeding insects are rarely important to the soybean producer. Refer to the North Carolina Soybean Scouting and Field Guide and the Soybean Insect Scouting Guide for North Carolina and Virginia for photos of the insects described below.

Foliage Feeders

Foliage-eating insects are present in almost all soybean fields throughout the season. Most fields rarely suffer yield loss, though, because the amount of leaf loss remains at low to moderate levels and soybean plants have the unique ability to compensate for foliage loss.

Armyworms
Multiple species

Biology and identification. Beet armyworm (Spodoptera exigua Hübner) caterpillar larvae are olive-green to near black and smooth, with a stripe down each side. A black spot appears on each side, just above the second pair of legs behind the head; there are three pairs of legs near the head, and four pairs of legs near the back plus a pair of legs directly at the back (4 + 1). Larvae fall and curl up into a “C” when disturbed. Small larvae web the underside of the leaf.

Fall armyworm (Spodoptera frugiperda J. E. Smith) caterpillar larvae are olive-green to dark brown and smooth, with a dark band above a stripe running down each side. The head is dark brown with a distinct cream-colored upside-down “Y” separating the eyes on either side of the head. Although corn earworm larvae also have an upside-down “Y” on the head, four black spots arranged in a square pattern appear on the top of the body near the rear of fall armyworm larvae. These are not present in corn earworm larvae. Fall armyworm larvae have three pairs of legs near the head and four pairs of legs near the back plus a pair of legs directly at the back (4 + 1).

Yellowstriped armyworm (Spodoptera ornithogalli Guenée) caterpillar larvae are pale gray to velvety black, with a yellow or yellowish-orange stripe running down each side. Above the stripe, a black triangular spot is found on nearly every segment of the body. Like the fall armyworm, a distinct cream-colored upside-down “Y” separates the eyes on either side of the head. Small black spots appear on each side of the first abdominal segment, further toward the rear compared with the side spots on the beet armyworm. There are four pairs of legs near the head plus a pair of legs near the back (4 + 1).

Both beet armyworm and fall armyworm are migratory insects and, as a result, are more prevalent later in the season. Yellowstriped armyworm overwinters in North Carolina and can be found throughout the season. Armyworms have multiple generations.

Injury and damage. Although yellowstriped armyworm can be found throughout the season, it only sporadically injures soybeans and generally in young stands. In contrast, the beet armyworm and fall armyworm chiefly affect late-planted seedling soybeans, and can be serious pests. Small larvae skeletonize the lower leaves. Large larvae feed over the whole plant. Severely damaged plants are very ragged in appearance. Beet armyworms often feed on and defoliate pigweed plants in and around soybean fields. They can also produce webbing that may be present on the underside of leaves. Noticing such damage can alert the scout that beet armyworm caterpillars may be present and moving toward a soybean field.

Economic threshold. The threshold for defoliating insects is 30% defoliation throughout the plant canopy two weeks prior to blooming (R1) and 15% defoliation throughout the plant canopy two weeks prior to flowering (stage varies) until the pods have filled (R7-R8). Vegetative soybeans are tolerant of adult feeding and, as seedlings become larger and faster growing, this foliage loss is seldom of concern. Recent studies have demonstrated that soybeans can tolerate nearly 100% foliage loss during the early vegetative stages before yield loss is achieved.

Management. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual. Note that both beet armyworm and fall armyworm have resistance to some insecticide classes and these are reflected in the insecticides listed in the manual for each insect.

Bean leaf beetle
Cerotoma trifurcata (Forster). Family: Chrysomelidae. Order: Coleoptera.

Biology and identification. This small dark colored beetle overwinters in woods around field edges and within soybean fields. Adult beetles are small, about 14 inch, have light yellow to reddish wings with four black spots (spots may be missing on some beetles), and a “V” pattern at the front of the wing covers. Immature beetles develop in the soil. Adult beetles generally emerge from overwintering before, and in synchrony with, soybean planting. Rainfall will delay emergence. The first full-season soybeans to sprout in an area will attract many of these strong flying beetles. There are two generations of bean leaf beetle in North Carolina.

Injury and damage. If colonization is heavy, bean leaf beetle can cause severe seedling defoliation, although this is very rare in North Carolina. Feeding appears as round holes eaten through the leaves, but larvae can also feed on developing root nodules. Bean leaf beetle adults can be pests in reproductive soybeans by feeding on leaves and scarring and clipping pods. Bean leaf beetle is rarely an individual pest in mid to late-season beans but can become a pest when other foliage and pod feeding insects are present. The exception to this general rule is when bean leaf beetle scars pods in seed production fields, affecting seed quality by providing a path of entry for seed infecting pathogens.

Economic threshold. The threshold for bean leaf beetle is 30% defoliation throughout the plant canopy two weeks prior to blooming (R1) and 15% defoliation throughout the plant canopy two weeks prior to flowering (stage varies) until the pods have filled (R7-R8). In severe situations, insecticides may check the population and prevent yield loss. Vegetative soybeans are tolerant of adult feeding and, as seedlings become larger and faster growing, this foliage loss is seldom of concern. Recent studies have demonstrated that soybeans can tolerate nearly 100% foliage loss during the early vegetative stages before yield loss is achieved. Whereas bean leaf beetle is a common insect of soybean seedlings in the Tidewater region, it seldom requires treatment at this locale or anywhere in North Carolina. Furthermore, bean leaf beetle almost never reaches economically important levels in the first generation, before soybeans have flowered. Therefore, it is more important for growers to scout for this insect mid to late-season.

Bean leaf beetle adults transmit several virus diseases to soybean plants, notably bean pod mottle virus, cowpea mosaic virus, and southern bean mosaic virus. The transmission of these viruses may become important on late-season soybeans after the virus has had a chance to build-up in the early season. However, managing bean leaf beetle with insecticides is not an effective way to reduce virus infection, and these viruses are rarely observed in North Carolina.

Management. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual. Organophosphate and pyrethroid-class resistance in bean leaf beetle has been documented in the Midsouth and has been reported in scattered areas of North Carolina. Always consult a label before application. General principles of Integrated Pest Management (IPM) should be followed, which include using multiple management tactics and the judicious use of insecticides.

Soybean looper
Pseudoplusia includens (Walker). Family: Noctuidae. Order: Lepidoptera.

Biology and identification. The defoliating soybean looper is a year-round resident of more southern areas, but it migrates into North Carolina each year. The immigration pattern is typically along the coast from south to north and spreading inland. Coastal counties south of Cape Lookout have the highest likelihood of economic infestation, although in some years infestations may spread above the Albemarle Sound and inland to I-95. The adult is a dark brown robust moth with a small silver-white figure eight spot on each forewing. Larvae are green with whitish lines along the length of the body and there are three pair of legs near the head, and two pairs of legs near the back plus a pair of legs directly at the back (2 + 1). In contrast, the similar looking, but rarely damaging green cloverworm, has three pair of legs near the head, and three pairs of legs near the back plus a pair of legs directly at the back (3 + 1). The body of the larvae is tapered from the rear (largest) forward to the head. Often the true legs and head are black. Larvae crawl with a distinct looping motion and may rest in this pose. The caterpillar favors the lower plant canopy and leaf underside, but will feed over the entire plant as defoliation progresses.

Injury and damage. This caterpillar is a voracious feeder and high-abundance populations can completely strip the foliage from fields; they do not feed on flowers or pods. Soybean looper moth populations peak in late August and colonize soybean fields. Peak larval populations occur in September, mostly on later planted soybeans and, as a result, double crop soybeans are the most susceptible.

Management. Soybean looper has developed resistance to many insecticide classes and its presence is often associated with the removal of predators and parasites by insecticide use for corn earworm management. Due to their habit of staying low in the canopy, on the leaf underside, insecticide performance is often negatively affected by poor coverage. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual.

Mexican bean beetle
(Epilachna varivestis Mulsant) Chrysomelidae: Coleoptera

Biology and identification. Adults are copper to yellow, rounded beetles with 16 black spots on their backs. Larvae are yellow, oval, soft-bodied, grub-like insects with darker, branched spines. This insect overwinters as an adult and lays yellow colored eggs vertically in masses on the underside of soybean leaves. There is only one generation a year, and there are four larval stages.

Injury and damage. Larvae and adults will feed on all parts of the plant, but injury is generally most severe on the foliage. Younger leaf tissue is preferred. Beetles feed between the leaf veins, causing a lacy appearance in heavily injured leaves. Because they feed on the underside of the leaf, patchy yellow and brown areas can often be visible on the tops of injured leaves. Mexican bean beetles attack soybeans throughout the season, but most damage occurs in August and September. Mexican bean beetles typically do not cause economic damage in North Carolina, but occasional severe infestations occur, especially in unusually cool, cloudy summers.

Economic threshold. The threshold for defoliating insects is 30% defoliation throughout the plant canopy two weeks prior to blooming (R1) and 15% defoliation throughout the plant canopy two weeks prior to flowering (stage varies) until the pods have filled (R7-R8). Vegetative soybeans are tolerant of adult feeding and, as seedlings become larger and faster growing, this foliage loss is seldom of concern. Recent studies have demonstrated that soybeans can tolerate nearly 100% foliage loss during the early vegetative stages before yield loss is achieved.

Management. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual.

Velvetbean caterpillar
Anticarsia gemmatalis (Hubner). Family: Noctuidae. Order: Lepidoptera

Biology and identification. The adult moth has a wingspan of 114 to 112 in. The forewings are ash gray, light yellowish-brown, or dark reddish-brown. The hind wings are cinnamon brown with a row of light spots near the margin. When the wings are fully extended, a dark diagonal line extending across both sets of wings is evident. A snout is visible in front of the head. Eggs are colored white, prominently ribbed, flattened on the lower surface, with a diameter of about 225 in., and turn pink before hatching. The sparsely haired larvae are 110 to nearly 2 inches long, depending on the stage, and vary in color from green to brown or black. Larvae have a light, dorsal stripe bordered by broad, dark stripes, and a broad, white, longitudinal stripe on each side. These larvae also have three pairs of legs near the head, and four pairs of legs near the back plus a pair of legs directly at the back (4 + 1) and thrash vigorously when disturbed. Pupae are 34 in. long, colored light green or brown, and have three pairs of hooked spines at the end of the abdomen.

The velvetbean caterpillar is a tropical species that does not overwinter in North Carolina. In most years, velvetbean caterpillar moths migrate into North Carolina during mid-summer to late-summer and colonize soybean fields. They may reproduce and reinfest late soybeans within the state; immigration from southern latitudes can also contribute to late-season population increases. Populations usually do not reach damaging levels; however, during occasional outbreak years (15% of years) many acres of late planted soybeans will become seriously infested. As with soybean looper, this insect occurs with much greater frequency in coastal counties from Cape Lookout and south. High numbers of velvetbean caterpillar seldom infest soybeans inland any further than about Lenoir County.

Injury and damage. Larger caterpillars have a voracious appetite and fields are sometimes stripped of foliage. If present at high numbers, pod clipping may occur after most foliage is consumed, but they prefer to feed on leaves.

Economic threshold. The threshold for velvetbean caterpillar is 30% defoliation throughout the plant two weeks prior to blooming (R1) and 15% defoliation two weeks prior to blooming until the pods have filled (R7-R8).

Management. Because this is a sporadic pest, there are no cultural practices that should be directed to velvetbean caterpillar management; despite this, growers should recognize that early maturing fields seldom receive economic infestations. Scouting, the application of thresholds, and treatment with insecticide on an as-needed basis are the primary management tactics. This insect can be killed with almost any class of insecticide and low rates can be successfully used. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual.

Pod Feeders

Pod feeders are the most dangerous insect pests because they directly attack soybean yield. Insecticide treatments should primarily target these insects when multiple species are present in a field. Scouting for these insects is essential as not all fields are subject to attack by pod feeders. Variety, row width, and planting date all influence which insect pests are present.

Corn earworm, cotton bollworm, soybean podworm
Helicoverpa zea (Boddie). Family: Noctuidae. Order: Lepidoptera.

Biology and identification. This insect has many common names (corn earworm, cotton bollworm, soybean podworm) because it feeds on a variety of crops. During the caterpillar life stage, the corn earworm is generally the most serious insect pest of soybean across North Carolina.

The coloration of the adult corn earworm can range from a light brownish-tan, rust-tan, olive-tan, to olive-colored; it is a fast flying moth with a 1- to 112-in. wingspan. This moth has greenish eyes and a prominent dark spot on each forewing (in contrast to the chevrons on the tobacco budworm forewing). The moths are active during the evening hours but can be commonly seen in fields during the day. Eggs are laid individually on soybean terminals, flowers, and leaves. Eggs are round and are a white to yellowish color. Their size is equivalent to a period in this text.

Caterpillars have three pairs of legs near the head, and four pairs of legs near the back plus a pair of legs directly at the back (4 + 1) and range in size from 116 in. (newly hatched) to 134 inch (last stage) long. When these larvae fall from the soybean plant they usually curl into a tight circle. Color varies considerably, but small larvae are usually brown with a dark head and larger larvae may range from green, yellowish, to black with distinct cream-colored bands running the length of the body; the head color on large larvae is usually an orange hue.

Following buildup generations in other crops, field infestations from this insect normally occur later during July and into August. Corn earworm overwinters as a pupa in the soil. The pupae change to moths in April and May and fly to whorl stage corn, or wild hosts, and lay eggs for the first generation. Following several weeks of development, first generation moths emerge around the time when corn pollinates and are strongly attracted to fresh corn silks where the eggs are laid that produce the second generation. Corn ears provide protection and a good food source to increase the population size of the second generation. After developing in the ears, larvae eat through the husk or crawl out through the top of the ear, drop to the ground, and pupate in the soil. Moths of the second generation emerge from corn fields, during the middle of July and into the middle August, where they seek soybean, cotton, peanut, sorghum, and other crop and wild host plants. This is often concurrent with the time period when soybeans are attractive to corn earworm (immediately prior to flowering until early pod-set).

There is also a September moth flight and very late-planted soybeans are sometimes suitable (not past blooming and early podding) for egg laying and small caterpillar survival. Yearly fluctuations in population may be great, with high populations often occurring during seasons of early warm and dry weather. In some years, a fourth generation may emerge. The July and August moth flight is monitored throughout North Carolina each year and presented as corn earworm or bollworm moth trap catches. This information can be very helpful for determining when to scout soybeans.

Injury and damage. On soybeans, the corn earworm may feed on foliage, flowers, and fruit. Eggs are laid over the entire plant, but small caterpillars must have tender vegetative terminals or flowers for good survival. Soybean fields that bloom during the moth flight are most likely to be infested above the economic threshold, although pre-bloom soybeans sometimes have high caterpillar abundance. Soybeans that bloom early, before the moth flight, usually escape infestation. The most serious yield losses occur when large corn earworm larvae coincide with soybean seed that have achieved almost full size. This is when caterpillars feed exclusively on seeds and have a big appetite to match their size. Feeding by small caterpillars on terminals, flowers, and small pods generally does not reduce yield unless environmental conditions are unfavorable for plant compensation during the late-season. A soybean plant produces many more flowers than it can convert into pods and seeds. Recent studies conducted in North Carolina have shown that corn earworm larvae can eat and injure flowers, but that the soybean plant nearly always compensates for this loss. Occasionally, large caterpillars will cause severe defoliation that will reduce yield.

Economic threshold. The threshold for corn earworm is dependent on the sampling method, cost of control, row width, and soybean price. The threshold does not decline when prices are above $10 per bushel because soybean can compensate for low levels of pod injury. An online calculator for determining the threshold level in podding soybeans can be used.

Management. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual. Populations of “corn earworm” in soybeans can sometimes be mixed populations of corn earworm and tobacco budworm (Heliothis virescens Fabricius). Tobacco budworm will often respond differently to insecticides than corn earworm, which is why identification is crucial for effective management.

The optimum timing for treating corn earworm in soybean is when most caterpillars are mid-size (12 to 34 in.). In this case almost all earworms will be killed if an effective insecticide is applied correctly and at a suitable rate. When caterpillars are very small (less than 38 in.), they are often found within flowers or flower clusters or between the folds of new leaflets. Furthermore, in most cases, even severe feeding on flowers will not lead to any yield loss. Treatment when most earworms are quite small will often result in poor control. Large caterpillars are easily killed in soybeans. Most damage (approximately 96%), however, is done during the last stages of growth, and waiting to treat may lead to damage before spraying is done. Since the objective of insect control is to balance economic loss from the insect and the cost of spraying, treatment of corn earworm should be directed against mid-size caterpillars.

Numerous cultural controls can help soybean producers minimize their risk for corn earworm. For example, corn earworm typically reaches the highest populations, and does the most severe damage, when soybean flowering is attractive for egg laying, canopies are open, and during periods of stress. Therefore, management practices that avoid these causes will help keep caterpillar numbers below threshold levels. Tactics that help maintain low populations include (1) using early maturing varieties (Group V and earlier) that are early planted, establishing favorable growth conditions (pH, fertility, moisture); (2) using narrow rows (that close the canopy quickly); and (3) avoiding soil systemic and foliar insecticides in early season. Creating an unattractive, healthy crop with high levels of biocontrol organisms will greatly reduce corn earworm infestation levels.

Stink bug
Multiple species

Biology and identification. Small stink bug nymphs (immatures) may be mostly black (southern green stink bug, Nezara viridula L.), reddish brown to pale green with black and white stripes on the abdomen (green stink bug, Chinavia hilare Say), pale yellow to tan with brown spots (brown stink bug, Euschistus servus Say), or orange to dark brown with a white stripe on the antennae and legs (brown marmorated stink bug, Halyomorpha halys Stål). Large nymphs (last two stages) are pale green with pink, black, and white markings (southern green stink bug), green with yellow and black markings or yellow with black markings (green stink bug), dull yellow/tan (brown stink bug), or tan to dark brown, with a white stripe on the antennae and legs (brown marmorated stink bug). Adults are shield-shaped and green to yellow green with red bands on the antennae (southern green stink bug), bright green with black bands on the antennae (green stink bug), brown with a yellow underside (brown stink bug), or brown with white angular spots on the outside edges of the rear abdominal segments, coppery patches on or near the head, and a white stripe on the next-to-last antennal segment (brown marmorated stink bug). The brown stink bug looks similar to a predatory stink bug, the spined soldier bug, but has rounded shoulders and a thin beak for plant feeding, whereas the spined soldier bug has sharp, pointed shoulders and a thick beak designed for spearing and consuming insects.

Stink bugs overwinter as adults in woodland areas and field edges and move into fields or to weedy hosts during the spring. Adults are very mobile and will often move among a variety of hosts. They pass their first generation in these hosts and the resulting adults are often found in flowering soybeans, although they are not damaging to the plants. Stink bug populations begin to build up in soybeans as the season progresses, and they are generally most common once other crops in the surrounding landscape have been harvested. They will undergo a second generation during late-summer, often in soybeans, before moving into overwintering sites as adults.

Injury and damage. These insects are most common in the mid and southern coastal counties of North Carolina, with the exception of brown marmorated stink bug, which is most common in the north and western counties. Of the four common species found in North Carolina, the southern green stink bug has the greatest damage potential, but is generally checked after cold winters. Brown marmorated stink bug can occur in very large numbers on field edges, especially those next to wooded areas or late-planted corn fields.

Stink bugs are important late-season insect pests of the soybean seed and reduce both yield and quality by their feeding. Although they can sometimes be found in flowering soybeans in relatively high numbers, they are not a problem until the pods begin producing seed. Although grain soybeans are affected by stink bug, seed soybeans are more vulnerable in terms of severity and frequency of loss. Stink bugs have piercing mouth parts and feed on tender terminals, blooms, pods, and developing seeds within pods. When feeding, both adults and nymphs inject digestive saliva into the plant, which helps liquefy plant tissues for easy extraction by the bug. The salivary fluid causes direct tissue injury and also can carry yeast organisms that grow within the seeds. Feeding may also create an avenue for pathogen entry into the plant. Germination and general seed quality can be affected by stink bug feeding. Additionally, feeding injury during early seed formation can result in aborted seeds and undersized, deformed seeds.

Economic threshold. Thresholds are based on row width, price of beans, and sampling method used. The threshold is cut in half for seed producers to be protective of germination. An online threshold table for determining the threshold level in podding soybeans is available.

Management. Stink bugs often occur in an uneven distribution within soybean fields. Adults move into fields from the edges and, therefore, may be more numerous along the margins during a colonization period. Eggs are laid in masses and, after hatching, the young nymphs remain in the same area until reaching an intermediate growth stage. Because of this clumping, individual scouting samples may give artificially high or low counts of small stink bugs, but these samples may not reflect the general stink bug population in the field. As stink bugs develop into larger nymphs and adults, they move throughout the field. Adult stink bugs are strong fliers and will move to soybeans of differing maturities as they enter the bloom/pod fill period.

Insecticide management of stink bugs relies on scouting and thresholds to identify where and when treatment is necessary, and the use of insecticides. Good application technique is very important when attempting to reduce stink bug abundance and recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual.

Stem Feeders

Stem-feeding insects regularly occur in soybeans but infrequently cause economic damage, with the exception of lesser cornstalk borer which can be a serious pest following burned wheat or in sandy soil.

Cutworm
Agrotis ipsilon (Hufnagel). Family: Noctuidae. Order: Lepidoptera.

Biology and identification. The black cutworm is a widespread species that can be found from southern Canada throughout the United States, Mexico, and South America. Each year in North Carolina, infested fields occur from the coast to the Tennessee state line. The threat of an infestation will be greatest in no-till or weedy corn fields, especially in poorly drained areas. The black cutworm feeds on a wide range of field and garden crops. Corn and tobacco are two of its preferred crops. Other known hosts include asparagus, bean, beet, cabbage, castor bean, cotton, grape, lettuce, peanut, pepper, potato, radish, soybean, spinach, squash, strawberry, and tomato.

The adult moth is characterized by long, narrow, usually dark forewings which are pale near the tips. There are three black dashes on each forewing. Hind wings are white with dark veins and broad, dark, indefinite margins. The wingspan varies from 112 to 2 inches. The egg is white, round, and about 150 inch in diameter. There are six larval instars ranging from nearly 15 inch to almost 2 inches in length, depending on the stage. Above the spiracles, the larva is generally a single color, varying from light gray to nearly black. The spiracles are distinctly black. When disturbed, the larva curls up. The brown pupa is about 23 inch long, with distinct mouthparts and antennae.

Moths of the first generation (overwintering) emerge between the middle of March and the first of May. They mature about the middle of May. Second generation moths emerge from late May to the middle of July. Third generation moths emerge between mid-July and late August. Fourth generation moths emerge during early September through December to produce the overwintering generation.

Between 5 and 11 days after emergence, each female begins to deposit about 1300 eggs in clusters of 1 to 30. Most eggs are laid on low, densely growing plants like chickweed, curly dock, and mustard; corn and soybeans are among the least attractive hosts for egg laying. The egg stage lasts 3 to 16 days, depending upon the temperature. These cutworms prefer moist soil where they are usually found in tunnels 3 to 4 inches beneath the surface. The destructive larval stage varies in duration from three weeks (or slightly more) in July to over four weeks in September. The July to August pupal stage lasts about two weeks; pupae that are in the soil during September may require as much as eight or nine weeks before adults emerge.

Injury and damage. Cutworms damage seedling soybeans by cutting the plant at the stem just below the cotyledons; usually no other feeding damage is present. These light gray to almost black caterpillars (from 34; to 112 inches long) commonly occur in soybean fields, especially no-till fields, but rarely kill enough seedlings to affect yield. During daylight hours, cutworms hide within the ground or under surface trash. Many larvae move from plant to plant on successive nights, while some stay to feed on the roots and underground stems of cut plants.

Economic threshold. There is no established threshold for cutworm. Also, most of the damage usually takes place on field edges, making the application of a threshold difficult. It might be possible to split fields up into different management zones. Keep in mind that vegetative soybean tolerates foliage feeding well, with little to no yield loss measurable up 50% defoliation, and possibly more, if environmental conditions are favorable. However, cutworms can reduce stands, and treatments may be needed in severe situations. Only treat if the pest is present.

Management. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual. It is rare, but occasionally fields may suffer enough damage to warrant treatment, if discovered in time. If cutworms are not discovered early enough, replanting may be necessary. Before replanting, it is a good idea to examine the field for the continued presence of cutworms and, if high numbers are present, treat the affected area when the replanted seedlings emerge. Cutworms are more of a problem in reduced tillage fields.

Lesser cornstalk borer
Elasmopalpus lignosellus (Zeller). Family: Pyralidae. Order: Lepidoptera.

Biology and identification. Adults are brownish with narrow forewings that are gray at the tips. The larvae are small caterpillars, with brown and white stripes and a blueish tinge. Larvae move in silken tubes near the surface of the soil and can move forward and backward very rapidly. Adult female moths lay eggs in soybeans and prefer dry soils over moist soils. Also, larvae are often found on double-cropped beans after burning, presumably because the soil is dryer as a result of the loss of ground cover and due to the increase in water-repellency of the soil (an unfortunate consequence from burning). In addition, the adult moths can sense smoke using their antennae. Presumably this could allow them to find freshly burned areas to lay their eggs. Dry soils also favor egg and larval survival.

Injury and damage. Lesser cornstalk borer larvae feed at the base of the plant, just below the soil surface. In doing so, they can girdle the main stem and lead to plant death or lodging. Lodging from this pest is usually irregular and occurs just at the soil surface. Feeding galleries are sometimes visible on the stem when bark is peeled back near the soil surface.

Economic threshold. There is no known economic threshold for this insect, since remedial management is difficult.

Management. Avoid planting soybean into burned stubble, planting late into droughty soils, or planting into fields that have been burned down with a herbicide less than two weeks prior. Lesser cornstalk borer larvae are highly adapted to dry conditions, with adaptations to help them retain water. As a result, some researchers suspect that these larvae can tolerate dry conditions while their predators cannot. For example, when fields are cooler and wetter, predators of lesser cornstalk borer, such as earwigs, are favored. Other insect predators such as big-eyed bugs, carabid beetles, robber flies and earwigs can also eat larvae.

Larvae and pupae can be killed by disease (viruses and the fungal organism Aspergillus flavus Link.) and parasites in addition to predators. Disease-causing organisms are nearly everywhere in the environment and their development is favored by moisture. Additionally, in order for this fungus to kill lesser corn stalk borer larvae, the larvae must be stressed.

Kudzu bug
Megacopta cribraria (Fabricius). Family: Plataspidae. Order: Hemiptera.

Biology and identification. Kudzu bug adults are about 14 inch long and are colored olive-green brown to dark brown with a shiny outer shell. They are strong fliers and emit a distinct odor, especially when disturbed. Nymphs are light green to dark brown and are hairy in appearance. The oldest nymphs have purplish wing pads. Eggs are barrel shaped, and are laid in a double line side-by-side, resembling a zipper.

Kudzu bug adults overwinter in forest debris and behind tree bark, but will also attempt to overwinter in structures such as houses and other buildings, where they can be a nuisance pest. When temperatures warm, the strong-flying adults emerge from overwintering sites and move onto hosts such as kudzu, wisteria, or soybeans where they mate, lay egg masses, and develop through five nymphal stages. The kudzu bug can complete development from egg to adult in six to eight weeks. After this first generation develops, additional adults are produced that will move into soybeans that may have been planted later.

Injury and damage. This insect taps into the veins of plants to reach the plant sugars, using piercing sucking mouthparts. As a result, injury to plants results from nutrient and moisture loss, rather than a direct loss of biomass from removal of plant tissue. Furthermore, sooty mold can develop on the leaves from the sugary excretion of the insect, reducing photosynthetic output. On soybeans, the kudzu bug adults and nymphs usually feed on stems, while small nymphs will feed on leaf veins, especially on the underside of leaves.

Economic threshold. Kudzu bug can be quickly sampled with a sweep net. Several randomly selected samples of 15 sweeps (defined as pendulum “swooshes” of the net) per sample should be taken from interior areas of the field. A threshold of one nymph-stage bug per sweep (i.e., 15 nymphs per 15-sweep sample) is recommended and may help reduce the need for multiple sprays. Kudzu bugs have not been shown to cause yield loss during the vegetative stages of soybeans and once the plants have reached the R7 stage. They can, however, delay maturity when present in high enough numbers.

Management. Because the migration of kudzu bug from kudzu to soybean takes place over several weeks, application of an insecticide is not recommended until nymphs are observed on soybean, even though densities of the migrating adults can be quite large. In North Carolina, the migration from overwintering sites begins in March and April. The second yearly migration of the first generation is expected to begin in July and continue mid-August. Field edges are colonized first, and then the bugs move to the interior of the field. Kudzu bugs are more common in conventional till, rather than reduced-till fields. Kudzu bugs are generally controlled by a fungus, Beauveria bassiana. If it is not, recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual.

Threecornered alfalfa hopper
Spissistilus festinus (Say). Family: Membracidae, Order: Hemiptera.

Biology and identification. Adults are green and wedge-shaped, and about 14 inch in length. The male is slightly smaller than the female and has a red or orange stripe on its shoulders. Eggs are white, oblong, and 125 inch long. They are slightly larger at one end, with a rough surface on the larger end of the egg. Nymphs are straw-colored, wedge-shaped, and heavily spined (hairy looking), with white legs, antennae, eyes, and a white abdomen.

Threecornered alfalfa hoppers overwinter as eggs in plant tissues or as adults protected by clumps of grasses. Young nymphs from overwintering eggs and overwintered adults begin feeding on weedy plants along field borders in the spring. Threecornered alfalfa hoppers prefer leguminous plants such as alfalfa, soybean, bean, cowpea, and sweet clover. Other plants occasionally infested include tomato, melon, wheat, barley, oat, Bermuda grass, and Johnson grass, as well as some trees and shrubs. During May or June, they migrate to soybean seedlings. Females then deposit 30 to 40 eggs, singly, in host plant stems. Nymphs hatch from the eggs two to six weeks later. They feed for 3 to 10 weeks before fifth instar nymphs molt into adults. On the average, 50 days elapse between egg deposition and adult emergence. The adults are strong flyers and readily migrate to new fields. Although the biology of this pest has not been studied in North Carolina, there are probably at least two generations each year.

Injury and damage. Threecornered alfalfa hopper damage may be detected from the seedling stage and into mid-season. Both the adults and nymphs feed on the soybean plant by piercing the main stem, branches, and leaf petioles with needle-like mouthparts and sucking sap. Typically, an insect will repeatedly feed at the same location on the stem, ringing the stem or petiole. This feeding causes a swollen, callused spot which is weak and will break during windy conditions. This can cause lodging of the main stem or lateral branches. In contrast to the lodging from lesser cornstalk borer, which is often irregular and at the soil surface, the lodging from threecornered alfalfa hopper is often a distinct, clean break, above the soil line. Petiole feeding and breakage of the lateral branches in not important because it does not lead to yield loss. Furthermore, lodging and breaking usually occur weeks after attack. There is some evidence that if damage is randomly scattered and occurs before bloom, in an optimum stand, reduction of at least 25% may be necessary to reduce yields. However, this rarely occurs in an economically damaging state in North Carolina.

Economic threshold. The economic threshold is one insect (adult or nymph) per sweep (defined as a single swoosh of the net). Once soybeans are above 10 in. tall, insecticide treatments do not impact yield, since the stems are thick enough so that feeding will not result in lodging. Threecornered alfalfa hoppers tend to be more common in double-cropped soybeans because their populations have built up through the year. It is difficult to use a sweep net to sample soybeans planted no-till because the stubble can hamper the sweep net.

Management. Damaging infestations of the threecornered alfalfa hopper can be avoided by destroying weedy borders around fields and by seeding a little more heavily. The first practice eliminates overwintering sites from which the bugs will migrate to soybeans. The second practice reduces the importance of the loss of a few plants. In the rare cases where the economic threshold is reached, recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual.

Grape colaspis
Colaspis brunnea (Fabricius). Family: Chrysomelidae. Order: Coleoptera.

Biology and identification. The oval, yellowish-brown adult beetle is just over 18 inch long, but less than ¼ inch. The wing covers appear striped due to the presence of longitudinal rows of shallow indentations. Eggs are smooth, range in coloration from white to yellow, and are about 1100 in. long. Larvae are around 14 in. long and “C” shaped. They are colored grayish-white or tan and are dark brown on the neck and head. They are stout and grub-like in form with three pairs of legs near the head and fleshy appendages on the abdominal segments.

Grape colaspis over-winters in the soil as a grub (larva) from the previous season. After overwintering below the plow layer, grape colaspis grubs move near the surface in later May and begin feeding on seedling roots. Once they complete development, they emerge as adults that seek out legume hosts to lay their eggs. Adults will lay eggs in the soybean field where they developed as larvae.

Injury and damage. Grape colaspis are harmful to soybean as grubs. They can injure plants by root feeding; damaged seedlings have few lateral roots and the underground stem may show feeding on the bark. Seedlings may die or be stunted from the feeding. Grape colaspis damage is often wrongly interpreted as nematode damage. However, it can be identified by the certain characteristic root and stem feeding signs. Often the presence of the adult beetles, which can feed in the plant’s foliar terminals, will aid problem identification. Foliage feeding by the emerged adults is insignificant. This insect will almost always be restricted to spots in the field and is most abundant on organic soils.

Economic threshold and management. There is no remedial treatment, and insecticides are ineffective to manage this insect. Hence, there is no economic threshold for grape colaspis.

Since adults lay eggs in the previous season’s soybeans, rotation is the best option to eliminate grape colaspis problems. Tillage is ineffective because larvae can overwinter below the plow layer. Replanted soybeans are seldom attacked because the larva responsible for the original injury will have transformed into beetles and emerged.

Grasshoppers and crickets
Various species

Biology and identification. Full-grown grasshoppers (which have wings) range in length from ¾ to 1 ½ in., depending on the species. Some grasshoppers are brownish-yellow or olive-green with contrasting black markings. On the hind femur, these markings resemble chevrons. The red-legged grasshopper has a reddish-brown back, a yellow belly and bright red hind legs. The two-striped grasshopper is greenish-yellow with contrasting black or brown markings. It has two light-color stripes that run from the head to the tips of the wings. Newly hatched nymphs are white. However, after several hours of exposure to sunlight, they assume the distinctive colors and markings of adults.

Crickets are coppery-brown to black, and the most commonly encountered cricket in soybeans is known as the field cricket (Gryllus spp.). Adults are black and, when full grown (with wings), are about 1 in. in length. Females lay their eggs in soil during in the fall. These eggs are the overwintering stage. They hatch when weather warms and the small immature wingless forms (nymphs) will begin to devour green foliage.

Injury and damage. Grasshoppers and crickets can be damaging in their immature wingless form (nymph), as well as the winged adult form. The most serious damage for soybeans occurs during the seedling stages. Grasshoppers and crickets can deposit egg cases into the soil of a previous crop. If soybeans are planted afterward, grasshoppers and cricket nymphs can emerge en masse and cut the stem of newly emerged seedlings just below the cotyledon seed leaves, causing the plant to die. Later in the season, grasshoppers can injure soybean plants by feeding on the foliage.

Economic threshold. The threshold for foliage feeding from grasshoppers and crickets is 30% defoliation throughout the plant canopy two weeks prior to blooming (R1) and 15% defoliation throughout the plant canopy two weeks prior to flowering (stage varies) until the pods have filled (R7-R8). In severe situations, insecticides may check the population and prevent yield loss. Vegetative soybeans are tolerant of adult feeding and, as seedlings become larger and faster growing, this foliage loss is seldom of concern. Recent studies have demonstrated that soybeans can tolerate nearly 100% foliage loss during the early vegetative stages before yield loss is achieved. Furthermore, most foliar injury from grasshoppers and crickets will take place on field edges, making the application of a threshold difficult. It might be possible to split fields up into different management zones to apply the threshold.

Like cutworm, there is no established threshold for grasshoppers and cricket feeding when seedlings are killed. However, producers should try to keep plant populations around 120,000 plants/acre for soybean planted in May, 150,000 plants/acre for soybean planted in June, and 170,000 plants/acre for soybeans planted in July.

Management. Recommended insecticides can be found in the North Carolina Agricultural Chemicals Manual. Immature grasshoppers and crickets can pose problems to soybean seedlings in reduced till situations, especially where the previous crop was pasture or forage (e.g., lespedeza); therefore, tillage and increasing the time between burndown of the cover crop, or harvest of the previous crop, can help.

Soybean aphid
Aphis glycines (Matsumura). Family: Aphididae. Order: Hemiptera

Biology and identification. Soybean aphid is an uncommon pest in North Carolina soybeans, and is more often encountered during cooler and cloudy summers. It uses an alternate host (buckthorn) to overwinter in the egg form. Soybean aphid is a close relative of the cotton aphid, which is commonly found in North Carolina, and is familiar to many producers. However, soybean aphid is the only aphid found in the United States that will develop large colonies on soybean plants. Adult soybean aphids are generally yellow, have black cornicles (cornicles are tail-pipe looking structures at the back of the body), and are approximately 116 inch long when fully grown. Young aphids look like adults without wings but are smaller. Adult aphids may be wingless or, during periods when they migrate, develop wings.

In the spring, eggs hatch into female winged soybean aphids. These adults can move on wind currents and do not need to mate. They move to soybean fields and begin laying living young but not eggs. New aphids may reach reproductive maturity in three to seven days (depending on temperature) and may double their population every five days under favorable conditions. Populations can expand rapidly. Aphids may infest vegetative stage soybeans and remain in the crop into the late reproductive period. Later in the season both males and winged adults appear in the population in response to plant chemical and photoperiod changes. These winged aphids can then move from the fields. These adults mate and lay eggs to pass the winter.

Injury and damage. Like kudzu bugs, soybean aphids suck sap from the veins soybean plants and cause plant stress. Sooty mold can develop on the leaves from the sugary excretion of the insect, reducing photosynthetic output. In vegetative stage plants, aphids are only a threat under very high populations that almost never occur in North Carolina. Reproductive stage soybeans are more sensitive to aphid damage, particularly in early reproductive stages (e.g., R1 – R3). Very high numbers of soybean aphid are capable of causing significant growth reduction, distorted foliage, and lower seed yields; however, this very rarely occurs in North Carolina. Soybean aphids are known vectors of a number of plant virus diseases. Examples of viruses spread by soybean aphid include alfalfa mosaic virus, soybean mosaic virus, and bean yellow mosaic virus.

Economic threshold. Scouting is achieved by examining plants for signs of aphids (e.g., disfigured leaves, ants on plants, cast aphid skins, honeydew on leaves) and aphids in plant terminals. Scouting begins in mid-vegetative stages and continues to R5 (seeds forming in pods); it is done weekly. Aphids are estimated on the leaves and an average of five samplings is compared to a threshold of 250 aphids per terminal leaf.

Management. Although soybean producers have access to many insecticides that are effective for soybean aphid management, the Extension recommendation for North Carolina producers is to rely on naturally occurring biological control agents, such as parasitic wasps, insect predators (especially certain bugs and beetles), and a parasitic fungal pathogen of aphids to keep aphids in check. Growers should avoid disrupting the field by spraying insecticides at the wrong time, or when they are unneeded, to allow biocontrol agents build up. Most spraying for corn earworm and other insects in North Carolina occurs after plants pass aphid-sensitive stages and will likely not conflict with aphid management. However, spraying earlier in the season can lead to higher aphid numbers.

Soybean Beneficial Insects

Beneficial insects are characterized as insects that destroy or feed on pest insects. They can limit or even prevent pest populations from becoming a problem on plants. Beneficial insects are typically placed in two categories: predators and parasitoids. Predators feed directly on pest species and parasitoids develop in or on pests.

Common Predatory Arthropods in Soybeans

Assasin bug. Various species. Family: Reduviidae. Order: Hemiptera. Several assassin bug species can be found in soybean fields. Adults have a long thin body with visible wings that cover the abdomen. Their legs are long and thin and many species have a pattern of orange and gray, green, or black on the legs. Immatures look similar, although they do not have wings and are a single color. They use their front legs to capture prey and a long thin beak to most commonly consume caterpillars and aphids. Although not aggressive, the insects can use their beak to bite humans, which can be painful from larger-sized species. Refer to the Soybean Insect Scouting Guide for North Carolina and Virginia for photos.

Big-eyed bug. Geocoris spp. Family: Geocoridae. Order: Hemiptera. Adults have large and wide eyes and brown and yellow coloring. Immatures have grey and black coloration with the same wide eyes as the adult. They are generalist feeders on insect eggs, small caterpillars, whiteflies, aphids, thrips, flea beetles, and spider mites.

Green lacewing. Chrysoperla spp. Family: Chrysopidae. Order: Neuroptera. Adults are green with lace-like wings and a soft body. Larvae are brown and yellow with an “alligator-like” shape and a tapered tail. Some adults can be predators, but it depends on the species. The larvae are generalist feeders that can feed on insect eggs, spider mites, thrips, aphids, small caterpillars, leafhoppers, mealy bugs, whiteflies, and psyllids.

Insidious flower bug and minute pirate bug. Orius spp. Family: Anthocoridae. Order: Hemiptera. Adults are oblong with a distinct white and black checkerboard pattern. Immatures are tiny and green to orange, with red eyes. These are generalist feeders that use their front legs to capture prey and a piercing sucking mouthpart to consume eggs, spider mites, and aphids. They can be especially useful to keep spider mites in check by feeding on their eggs. Refer to the Soybean Insect Scouting Guide for North Carolina and Virginia for photos.

Ladybird beetles (ladybugs). Various species. Family: Coccinellidae. Order: Coleoptera. Adults have a dome-shaped body on top, which is flat on the bottom. Their antennae and legs are short and they have red to orange or pink coloring with varying number of dark spots. The larvae have an alligator-like shape and can have blue, yellow, orange and red markings. The eggs are yellow or orange and laid in clusters or singly.

Damsel bugs (Nabid bugs). Various species. Family: Nabidae. Order: Hemiptera. Damsel bugs are brown colored with narrow heads and a long piercing-sucking mouthpart that is typically tucked under the body. The nymph looks similar to adults, but does not have fully developed wings. They feed on caterpillar eggs and larvae, aphids, spider mites, fleahoppers, leafhoppers, treehoppers, and Lygus bugs.

Spined soldier bug. Podisus maculiventris (Say). Family: Pentatomidae. Order: Hemiptera. The spined soldier bug is a stink bug that has a broad shoulder pointed outwards into a point. It is typically brown colored and can often be confused with stink bug pests. For quick identification, look for the pointed shoulders, alternating black and orange markings on the sides under wings, and a beak that is twice the width of the antennae. Spined soldier bugs prefer to feed on caterpillars, but they have also been documented feeding on Colorado potato beetles, Mexican bean beetles, and Lygus bug nymphs.

Predatory mites. Various species. Predatory mites are very small and prey on pest mite species. They can be located on the underside of leaves and near the midrib. They are generalist feeders, but prey heavily on spider mites.

Common Parasitoids in Soybeans

Ichneumonid wasps. Ichneumonid wasps are black and have a relatively light coloration on the legs with a slender long body. Females have a long ovipositor at the tip of their abdomen. They can parasitize internally or externally and mainly attack caterpillar larvae and pupae.

Braconid wasps. Braconid wasps look similar to Ichneumonid wasps. They tend to be internal parasitoids but will pupate outside the host’s body. They attack the larvae of caterpillars, beetles, and flies and can be an important parasitoid of aphids.

Tachinid fly. Tachinid flies look like houseflies but can vary in size and shape. They are hairy, black, grey, or can be striped colored. They attack caterpillar larvae, beetles, grasshoppers, and true bugs (i.e., stink bugs and kudzu bugs).

Author:

Associate Professor and Extension Specialist
Entomology and Plant Pathology

Publication date: Nov. 21, 2017
Last updated: Jan. 3, 2018
AG-835

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