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Corn
Volume 57 Number 8 Date 05/30/2012 EUROPEAN CORN BORER - The spring flight has peaked in the southern and central areas. Larvae resulting from the flight are in the early instar stages and fresh whorl-feeding injury should become evident during the first two weeks of June. The optimal treatment window for first generation corn borers has opened in the southernmost areas of the state with the accumulation of 800 degree days (base 50°F), although no Wisconsin corn field qualifies for treatment at this time. TRUE ARMYWORM - Larval infestation rates ranged from 1-12% in corn fields examined from May 24-30. These averages are considered non-economic, but actual populations may be larger and more widespread than indicated by our surveys. Continued scouting of corn and small grains is strongly advised this month. In addition, the DATCP black light trapping network continues to report significant moth flights, indicating the potential for a consistent population of first generation larvae for several more weeks. STALK BORER - Migration of stalk borer larvae from grasses and broadleaf weed hosts into corn is expected to accelerate next week. Spot treatment may be warranted for corn fields that show 10% of plants with larvae or leaf feeding. Damage should become pronounced by mid-June. --Krista Hamilton, DATCP Entomologist 
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