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Considerations for controlling soybean aphid multiplication.

Agronomy Bulletin 83 ─ Soybean Aphid Management

Soybean aphids ─ which can clip yields by 40 percent in severe cases ─ are marked by two distinct black cornicles

Situation

Since their 2000 United States debut, soybean aphids have proven to reduce yields by up to 40 percent while exposing soybean crops to other potential pest problems. Under the right circumstances, insecticide applications can help growers manage crop losses.

Factors to Consider

  • Life cycle
  • Field history
  • Conditions for reproduction
  • Pest pressure
  • Scouting
  • Insecticides

Action Plan

  1. Understand soybean aphids' rapid life cycle. In the fall, aphids lay eggs and overwinter on their host, buckthorn. After the eggs hatch in the spring, the aphid will sexually produce two to three generations on buckthorn. Then, winged females invade soybean fields in early June. These females are fertile without mating, allowing a single aphid to produce up to eight offspring per day for 10 to 20 days. Soybean aphid populations can double in a field in only two to three days if temperatures are between 70 F and 77 F with low humidity. Aphids feed on leaves and stems, removing significant amounts of water and nutrients, causing plant symptoms such as leaf puckering, stunted growth, reduced pod count or reduced seed size.
  2. Routinely scout throughout the summer. Soybean aphids usually attack between late May and late August, typically on the underside of the upper soybean foliage. Two distinct cornicles, which under magnification distinguish the soybean aphid from thrips and spider mites, accentuate the pest’s yellow frame. Sample leaves and stems from at least 20 plants — particularly in fields with previous aphid infestations — to determine whether soybean aphids have reached an agronomic threshold as outlined in the table.
  3. Correlate soybean aphid infestations with other problems. Aphids secrete honeydew, a sticky waste product that causes sooty mold to cover the leaf surface. This blocks light and stunts photosynthetic rates, slowing growth and reducing pod counts. Soybean aphid feeding also creates openings in leaves for other plant pathogens to attack.
  4. Apply insecticides if it makes agronomic sense. Soybean aphids are very manageable. Insecticides such as Cobalt&#174; offer excellent control, but timing and plant coverage is critical for maximized efficacy. Choose insecticides with a longer residual.
 

Summary

Given soybean aphids’ ability to rapidly reproduce, scout your fields early and often. If it makes agronomic sense, apply a foliar insecticide for optimum control. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Resources

Published on Tuesday, July 15, 2014