Soybean Aphid Numbers Building-Time for Scouting

Soybean Aphid Population-Southern Henry County 2011

by Greg LaBarge, Fulton County

Friday afternoon I was in Archbold, Wauseon, Custer (OARDC Branch) and Holgate. I stopped at 19 different soybean fields along the way and found soybean aphid in all but 2 fields. All but two field had soybean aphid that were easily found. Number would be 3-70 per plant with many in the 20-50 range. Greatest numbers were in Fulton County but there was a hot spot in Henry. See picture to the left. Aphids were on the OARDC Branch as well. Soybeans are in R3-R4 stages generally. Did not see lady beetles.

Threshold number for aphids remain a rising population reaching 250 aphids per plant. Sample several areas in the field with at least 30 plants per 20 acres to come up with that average. The type of infestation pictured would near 250 but remember we are talking about average infestation for multiple plants not just a single plant 250. We need to be concerned with aphids until we reach R6.

Some scouting keys:

  • At this point look at the growing point and leaf below the growing point.
  • The picture to the left is more than 250 aphids.
  • A colony that covers all sides of the stem for 1 inch is 250-300 aphids.
  • A speed scouting method has been tested in the west. A copy of the sheet from Minisota can be found at:

They are easily controlled with insecticides but keep in mind in you have bee hives in the 1/2 mile of your field to notify the beekeeper on your intent to spray.

Other Insects found:

Spider mites: Are found in southern Henry who in the SW have missed rains. Generally along the edge but edge in areas have totally bronzed plants.

Bean leaf beetle: Beetles are being seen again.

Green Cloverworm, grasshoppers, white flies, Japanese beetle and potato leafhopper were amoung the other insects seen.

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