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Forages & Grains
Volume 59 Number 4 Date 05/22/2014 ALFALFA WEEVIL - Larvae were collected for the first time this season on May 19 in Richland County. Surveys conducted in the south-central and southwest areas found low counts of 1-3 per 100 sweeps in less than 10% of fields checked. Regular sampling for larvae and leaf tip feeding should begin at 300 degree days (sine base 48°F), or by May 23 near Madison, May 27 near Hancock and May 29 near Eau Claire. POTATO LEAFHOPPER - The first distinct migration occurred last week and leafhopper adults are now distributed in low numbers across southern Wisconsin. Migrants were collected from 11 of 39 (28%) alfalfa fields sampled this week, as far north as Westby in Vernon County. This insect customarily appears in Wisconsin as the first alfalfa crop is harvested and under favorable conditions can rapidly increase to damaging levels in the second crop. TARNISHED PLANT BUG - Adults are more numerous than last week, but counts in alfalfa remain low. Surveyed fields in Dane, Green, La Crosse, Richland, Rock and Vernon counties contained an average of nine per 100 sweeps compared to five per 100 sweeps last week. The economic threshold for plant bugs in alfalfa is extremely high at five per sweep (or 500 per 100 sweeps) and is seldom exceeded until July or August. PEA APHID - Alfalfa sampled this week contained counts of 1-225 aphids per 100 sweeps. Reproduction has not yet started. -- Krista Hamilton, DATCP Entomologist 
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