Volume 63 Number 16 Date 08/23/2018
SOYBEAN APHID - Densities recorded during the annual survey this month were low, aside from a few high-population fields in the west-central area where reports indicate scattered soybean fields were treated earlier this month for aphid control. The state average count in 190 fields sampled from July 23-August 20 is 14 aphids per plant, with only two surveyed fields showing above-threshold populations of 260 and 290 aphids per plant. For comparison, the 2017 survey found an average of six aphids per plant, the 2016 average was eight aphids per plant, averages from 2013-2015 ranged from 35-55 aphids per plant, and surveys from 2010-2012 documented counts of 7-16 aphids per plant. The lowest state average in the 17-year history of Wisconsin soybean aphid surveys was six aphids per plant, in 2017. Although some localized fields developed economic populations (>250 aphids per plant) by first week of August, survey results suggest that widespread treatment for aphid control has generally not been required this season.
JAPANESE BEETLE -Defoliation has been observed in 52% of the soybean fields examined in late July and August. Last season, 87% of surveyed fields had some degree of Japanese beetle feeding. Counts taken during the aphid survey ranged from 1-140 beetles per 100 sweeps, with a state average of eight per 100 sweeps. The highest counts of 50-140 beetles per 100 sweeps were recorded in Grant, Jefferson, Trempealeau, Walworth counties. Although some beetles may persist into September, much of their activity should decline in another two weeks.
-- Krista Hamilton, DATCP Entomologist