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Soybean aphid


  • Adult: Small, soft-bodied, yellow to green aphids that appear in colonies on bean leaves. Some females develop wings so they can start new colonies on other plants.
  • Nymphs: Like adults but smaller and wingless.
  • Eggs: Females do not lay eggs but give birth to live young.  

Timing of damage: V2 to R6

Type of damage: Aphids suck the sap out of plants. Soybean plants will appear stunted and have poor canopy development. Some leaves may turn gray or black due to sooty mold that grows on the aphid excretions (honeydew).

Scouting: Check 20 plants in various field locations and determine the average number of aphids per plant. Also look for lady beetles or ants that feed on soybean aphids.

Economic threshold: An average of 250 or more aphids per plant in growth stages R1 to R6.

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