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Forages & Grains
Volume 57 Number 8 Date 05/30/2012 ALFALFA WEEVIL - Larvae are common but not numerous in second crop alfalfa. The average count in the past week was 1 per sweep, with 10-70% leaf tip feeding. Individual fields in Green and Richland counties showed 2-4 larvae per sweep and 50-70% defoliation, but these cases were exceptional. Damage is expected to subside by early to mid-June as the remaining third and fourth instar larvae enter the non-feeding pupal stage. POTATO LEAFHOPPER - Numbers have not changed significantly since the last report. Representative counts in the southern, central and east-central areas range from 0.1-1.2 per sweep, with an average of 0.4 per sweep. As of May 30, economic populations have not been noted in any DATCP-surveyed alfalfa field. PLANT BUG - Alfalfa fields in the southern half of the state are showing low populations of 0.2-1.5 per sweep. The economic threshold is 5 per sweep. Nymphs are now more abundant than adults in most fields. PEA APHID - Surveys in Calumet, Dane, Fond du Lac, Grant, Green, Iowa, Lafayette, Richland, Rock, Sauk and Vernon counties yielded variable counts of 0.7-8.0 per sweep and an average of 3.2 per sweep. Populations have declined slightly with the recent heavy rain and harvesting of first crop alfalfa. --Krista Hamilton, DATCP Entomologist 
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