Soybean IPM
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).
Helpful Links:
- 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.
- Common Insect Pests in Tennessee (Part 1 – 10 minute video)
- Common Insect Pests in Tennessee (Part 2 – 15 minute video)
- Insect Scouting in Soybean (9 minute video)
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.
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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.
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* 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.
When Applying Insecticides: Read and follow label directions carefully before you buy, mix, apply, store or dispose of a pesticide. According to laws regulating pesticides, they must be used only as directed by the label. Alternate classes of insecticides when practical to minimize the chance of developing resistance. When pollinators are present, and especially when beehive are located near fields, apply pesticides in a way to minimize risks to bees and other non-target organisms.
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.
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