Volume 63 Number 10 Date 07/05/2018
SOYBEAN APHID - Levels of this insect remain well below the economic threshold of 250 aphids per plant and 71% of the 49 soybean fields surveyed in the past two weeks still had no detectable populations. Average counts at the sites sampled from June 21-July 4 were less than one aphid per plant and seven per infested plant, based upon examination of 100 plants per field. The highest total count was only 41 aphids on 15 of 100 plants (three aphids per infested plant) in a Fond du Lac County field.
Despite the low sample numbers, aphid populations could increase rapidly in flowering soybean fields and economic densities may develop later this month. This pest requires consistent monitoring from now until the R5.5 stage of soybean growth in August.
DEFOLIATORS - Defoliation is common but light in surveyed fields, usually affecting 2-10% of plants. The leaf feeding insects observed during recent surveys were the rose chafer, bean leaf beetle, Japanese beetle, sand chafer, slugs and various caterpillars (including hitched arches larvae and the silver-spotted skipper caterpillar). Defoliation rates have not exceeded the 20% economic threshold for soybeans in the bloom stages as of July 5.
-- Krista Hamilton, DATCP Entomologist