Volume 64 Number 11 Date 07/11/2019
SOYBEAN APHID - Levels of this insect remain very low. In fact, 30 of the 33 (91%) soybean fields surveyed this week still had no detectable aphid population. Average counts at the sites sampled from July 4-10 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 37 aphids on 1 of 100 plants 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 by early August. 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 1-5% 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 thistle caterpillars and the silver-spotted skipper). Defoliation rates have not exceeded the 20% economic threshold for soybeans in the early bloom stages as of July 11.
-- Krista Hamilton, DATCP Entomologist