|
|
|
Forages & Grains
Volume 64 Number 4 Date 05/23/2019 ALFALFA WEEVIL - Larvae were collected for the first time this season on May 22 in Iowa and Grant counties. Surveys in the south-central and southwest areas found low counts of 1-3 per 100 sweeps in about 10% of alfalfa fields checked. Regular scouting to assess leaf feeding damage should begin next week and continue through first harvest and early second-crop regrowth. A defoliation level of 40% of stems with weevil feeding in the first crop signals the larval population is high and an early harvest would be beneficial. POTATO LEAFHOPPER - A migration appears to have occurred in the past week, with leafhoppers collected from 17 of 40 (43%) alfalfa fields sampled from May 20-22. This insect arrives annually in Wisconsin in mid- to late May, as harvest of the first alfalfa crop is approaching. These long-distance migrants are predominantly mated females which arrive ready to lay eggs and initiate a new generation. PEA APHID - Alfalfa sampled this week contained low counts of 1-65 aphids per 100 sweeps, an increase over the 1-35 per sweep last week. TARNISHED PLANT BUG - Adults are common in alfalfa, though counts remain very low. Surveyed fields in Dane, Grant, Iowa, Monroe, Sauk and Vernon counties contained an average of six per 100 sweeps. The economic threshold for plant bugs in alfalfa of five per sweep (or 500 per 100 sweeps) is seldom exceeded until July or August. -- Krista Hamilton, DATCP Entomologist 
|
|