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Corn
Volume 58 Number 12 Date 07/25/2013 WESTERN BEAN CUTWORM - Pheromone traps produced very few moths in the past week, despite very favorable nightly temperatures. The highest count was 29 moths near Marcellon in Columbia County. Peak flight, or 50% emergence of the adult population, should occur around 1,422 degree days, or from August 1-8 at most southern and central sites. Degree day accumulations (base 50°F) as of July 24 were 1,512 at Madison, 1,383 at Eau Claire, 1,342 at Hancock and 1,322 at Appleton. Oviposition on corn and dry beans has been under way since early July and is increasing. Treatment may be required for field corn with infestations affecting 5% of the plants at 90-95% tassel emergence. The economic threshold is 4% for processing sweet corn. EUROPEAN CORN BORER - The second flight began in the last reporting period with the capture of 1-11 moths from Janesville to Chippewa Falls. The appearance of summer moths signals that eggs are being deposited on corn, pepper, potato, snap beans and other vegetable hosts. At current temperatures, black light traps could register peak emergence during the second week of August in the southern and central districts. The treatment window for second generation larvae extends from 1,550-2,100 degree days (base 50°F). CORN EARWORM - Moderate flights of 20-47 moths were registered at the Chippewa Falls, Sun Prairie, Wausau and Watertown pheromone trap sites during the last reporting period. Sweet corn growers statewide can expect corn earworm infestations by early to mid-August if silking fields are not monitored and treated promptly. Control is advised for counts of 5-10 moths in three consecutive nights and should be applied every 2-5 days until silks turn brown. The economic threshold for tomatoes is seven moths per trap per week. Counts in the past week were as follows: Chippewa Falls 21, Coon Valley 0, Cottage Grove N 8, Green Lake 5, Janesville 1, Marshfield 2, McFarland 2, Ripon 4, Sun Prairie N 20, Sun Prairie W 6, Watertown 28 and Wausau 47. -- Krista Hamilton, DATCP Entomologist 
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