Forages & Grains
Volume 65 Number 17 Date 08/27/2020
POTATO LEAFHOPPER - Counts were below economic levels (< 2.0 per sweep) in most fields surveyed during the last week of August, with a few exceptions in the dry west-central counties where scattered sites had 2.5-3.0 per sweep. Some alfalfa stands are exhibiting moderate to severe yellowing, though the symptoms are likely due to moisture stress, late-summer diseases, nutrient deficiency, or a combination of these factors, since high leafhopper pressure was not recorded in these fields. Nymphs remain common in sweep nets, but a significant population decrease should occur by mid-September.
PEA APHID - Dry weather appears to have favored aphids in the last 2-3 weeks and counts in some western Wisconsin fields have increased to 10-12 per sweep for the first time since June. Most sites sampled had lower populations in the range of 2-5 aphids per sweep. Pea aphid population growth usually slows during periods of extreme heat, but the lack of rain this month may have limited development of fungal pathogens and other natural enemies that would ordinarily suppress aphids late in the season.
-- Krista Hamilton, DATCP Entomologist