Fall Armyworm, Beet Armyworm, and Yellowstriped Armyworm
Bean Leaf Beetle
Blister Beetle, Japanese Beetle, and Mexican Bean Beetle
Other Defoliating Caterpillars
Threecornered Alfalfa Hopper
Many different insects can be found on soybeans in Tennessee. Many times insecticides are not needed for control, but in some cases, damaging populations are not noticed until serious damage has already occurred. The most economical and effective pest management program begins with scouting, proper insect identification, and a determination of possible economic damage. Some of these pests feed on leaves and stems and others are primarily pod feeders. Soybean fields should be scouted weekly, paying special attention during the first two weeks after emergence and during the time of full bloom (R2) to full seed (R6).
- UTcrops.com (comprehensive information for crop management)
- Insect Control Recommendations for Field Crops (PB 1768)
General Scouting Procedures
A good sampling plan is to take 25 sweeps at 4 locations in average sized fields (about 50 acres). Increase sampling points proportionately with the acreage in a field. Make sure sample points are scattered over the entire field.
Seedling/Stem Feeding: Check seedlings very closely until the plants are about 12 inches tall. The stems become woody and severe damage from seedling pests becomes less likely at this time. Look for insects that may be on the plant (threecornered alfalfa hopper) or in the soil around the base of the plants (lesser corn stalk borer, cutworms). Evaluate stand loss (percentage of dead or dying plants) and try to determine if future stand loss is probable (insects easily found and actively damaging plants).
Foliage Feeders: Determine what insects are eating the foliage and estimate percent defoliation. Use a sweep net or a drop cloth (shake sheet) to sample for insect pests. At each sample point, estimate percent foliage loss so that an average can be calculated for the field.
Pod-Feeders: After full bloom, when pods are forming, look closely for any pod-feeding caterpillars (corn earworms and fall armyworms) and stink bugs which are caught in a sweep net.
Representation of Percent Defoliation: Inexperienced scouts often overestimate percent defoliation. Use the image below to help calibrate your estimates, but ratings should be for the entire canopy, not just upper canopy leaves.
Expected Occurrence of Insect Pests in Soybean
Below is a timetable of when common pests are typically encountered in soybean, although conditions vary from season to season or farm to farm within a season.
|Stage of Plant Development||Common Pests||Occasional Pests|
|Seedling||Threecornered alfalfa hopper||Thrips, grasshoppers, bean leaf beetle, cutworms, grape colaspis, white grubs|
|V5 - R1 (Early flowering)||---||Threecornered alfalfa hopper|
|R1 - R5 (Early flowering to early podfill)||Stink bugs, green cloverworm||Threecornered alfalfa hopper, blister beetles, corn earworm, fall armyworm, loopers, soybean aphid, kudzu bug|
|R5 + (mid to late podfill)||Stink bugs, loopers, green cloverworm||Blister beetles, fall armyworm, loopers, soybean aphid, kudzu bug|
Insecticide Seed Treatments
Insecticide seed treatments such as thiamethoxam (e.g., Cruiser), imidacloprid (e.g., Gaucho, Acceleron I), and clothianidin (e.g., NipsIt Inside) are available from seed companies or local distributors. Seed treatments will help control some seed and seedling pests such as thrips, bean leaf beetle, grape colaspis, threecornered alfalfa hopper, wireworms and white grubs. Data indicates that insecticide seed treatments provide an average yield increase of 1-1.5 bushels per acre in Tennessee. Insecticide seed treatments are recommended when cover crops are planted and persist in fields within 3 – 4 weeks of planting, especially if the cover crop includes a legume species such as vetch or winter peas.
|When to Treat|
|Threecornered Alfalfa Hopper||Treat if 10 percent of young plants (up to 10-12 inches) are infested with adults or nymphs. Bend small plants over to check for girdling and consider treatment if 50 percent or more of plants are girdled. Treatment is not generally recommended for plants greater than 12 inches tall.|
|Defoliating Pests (bean leaf beetles, green cloverworm, blister beetles, loopers, grasshoppers, Japanese beetles, etc.)||Treat at 30% defoliation until bloom (R1), 20% from bloom to full seed (R1-R6), and 30% after R6 to R6 plus 7-10 days.|
|Alternatives to defoliation thresholds during pod filling (R1-R6):|
|Bean leaf beetle – 50 beetles per 25 sweeps|
|Green cloverworm – 38 larvae per 25 sweeps|
|Loopers – 19 larvae per 25 sweeps|
|Stink Bugs||From beginning bloom (R1) to full seed (R6), treat when an average of 9 or more stink bugs is found per 25 sweeps (or 1 stink bug is found per foot of row). From R6 to R7, treat when an average of 18 or more stink bugs is found per 25 sweeps. *|
|Corn Earworm||See table for treatment thresholds based on sweep net sampling, or consider treatment once blooming has begun if an average of 1 or more larvae is found per foot of row.|
|Fall Armyworm||Once blooming has begun, treat when an average of 9 or more larvae is found per 25 sweeps (or 1 or more larvae is found per foot of row). Fall armyworm may also feed on foliage, and severe infestations may originate on weedy grasses. Treatment can be based on the percent defoliation thresholds above under these circumstances.|
|Soybean Aphid||Treat when an average of 250 aphids or more is found per plant from early bloom (R1) until early pod fill (R5). Treatment after R5 is less likely to increase yield.|
|Kudzu Bug||Treat between emergence and R1 when 5 or more kudzu bugs are found per plant. From R1 to R7, treat when an average of 1 or more immature kudzu bug is present per sweep (25 per 25 sweeps).|
* In soybeans planted on 36-inch or wider rows, sweep only one row. In narrow-row soybeans, allow the normal arch of a sweep net to continue through the adjacent rows.
Premixed Insecticide Products: The following products are available as premixes of two or more insecticides. The use of premixes may provide suppression or control of multiple pests, and thus are typically recommended when several pests are present at treatment level.
|Trade Name (Insecticides)||Amount Product per Acre||Primary Target Pests (see label for other pests that may be controlled)|
|Besiege (chlorantraniliprole, λ-cyhalothrin)||5 - 10 oz||Caterpillars, stink bugs, threecornered alfalfa hopper, kudzu bug|
|Brigadier (imidacloprid, bifenthrin)||4 - 6.1 oz||Corn earworm, green cloverworm, stink bugs, kudzu bug|
|Cobalt Advanced (chlorpyrifos, γ-cyhalothrin)||22 - 38 oz||Stink bugs, corn earworm, green cloverworm, threecornered alfalfa hopper|
|Double Take (diflubenzuron, λ-cyhalothrin)||2 - 4 oz||Green cloverworm, stink bugs, threecornered alfalfa hoppers, kudzu bug, grasshoppers|
|Endigo ZC (thiamethoxam, λ-cyhalothrin)||3.5 - 4.5 oz||Stink bugs, corn earworm, green cloverworm, threecornered alfalfa hopper, kudzu bug|
|Hero (bifenthrin, Z-cypermethrin)||4 - 10.3 oz||Stink bugs, corn earworm, green cloverworm, threecornered alfalfa hopper, kudzu bug|
|Intrepid Edge (methoxyfenozide, spinetoram)||4 - 6.4 oz||Most caterpillar pests|
|Justice (acetamiprid, bifenthrin)||3 - 5 oz||Bean leaf beetle, aphids, armyworms, kudzu bugs|
|Leverage 360 (imidacloprid, β-cyfluthrin)||2.8 oz||Stink bugs, corn earworm, green cloverworm, threecornered alfalfa hopper|
|Stallion (chlorpyrifos, Z-cypermethrin)||9.25 - 11.75 oz||Stink bugs, corn earworm, green cloverworm, threecornered alfalfa hopper|
|Triple Crown (Z-cypermethrin, bifenthrin, imidacloprid)||3.5 - 4.8 oz||Stink bugs, corn earworm, green cloverworm, threecornered alfalfa hopper, kudzu bug|
Rating Scale: 0 = no control, 10 = excellent. The performance ratings in the chart are for comparison purposes only and are not necessarily a measure of percent control.