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Forages & Grains
Volume 60 Number 20 Date 12/03/2015 POTATO LEAFHOPPER - Populations remained consistently low all season long. Migrants first arrived during the week of April 26 and were distributed in low numbers across the southern half of the state by May 20. Nymphs appeared in second crop alfalfa by June 11. Economic counts of two or more leafhoppers per sweep were not observed in any of the 433 alfalfa fields surveyed in 2015, and widespread leafhopper control was not necessary. ALFALFA WEEVIL - Larval emergence began in southern Wisconsin by May 11. Development accelerated during the latter half of the month and weevils were abundant by early June. Excessive rainfall during the first alfalfa harvest permitted larval populations to increase to economic levels and severe defoliation (40-60%) became evident in scattered fields by June 4. Carryover of larvae into the second crop was common, but the damage subsided by late June as remaining larvae pupated. PEA APHID - Counts peaked at approximately 19 aphids per sweep from June 11-17 then abruptly collapsed after the first cutting. Surveys yielded very low populations during the balance of the season and no direct damage to alfalfa was attributed to this insect in 2015. CEREAL LEAF BEETLE - Larvae were the cause of light to moderate defoliation of wheat in Columbia, Dane, Rock, Sheboygan and Winnebago counties during the last two weeks of June. Economic populations were not observed, though in Dane County it was reported that 10-25% of the flag leaves were damaged in several fields. The larval feeding period was brief and ended by July 4 in southern and eastern Wisconsin. Most of the infestations noted in June were minor and no yield impact was expected. -- Krista Hamilton, DATCP Entomologist 
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