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Forages & Grains

Corn

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Degree Days

Corn
Volume 61 Number 12 Date 07/21/2016


WESTERN BEAN CUTWORM - Moth emergence accelerated with the warm weather of the past week and has peaked in some areas. According to the degree day model for this insect, 25-50% of the adult population has emerged in the south-central, southwestern and west-central counties, 10-20% has emerged in the southeast and east-central counties, and emergence is beginning in the northern areas. The DATCP network of pheromone traps registered 644 moths from July 14-20, compared to 43 moths during the previous week. The state cumulative count thus far is 715 moths in 72 traps. Oviposition on corn and dry beans is intensifying. Scouting and possible treatment of economic infestations (8% of corn plants or 4% of sweet corn plants infested at 90-95% tassel emergence) is advised in the week ahead.

EUROPEAN CORN BORER - Surveys at 39 sites this week found only two significant infestations affecting 40-52% of corn plants in Monroe and Vernon County fields. Fifth-instar larvae, pupae and new moths were the predominant developmental stages in the southern and west-central areas. The treatment window for the second larval generation has opened near Beloit, La Crosse, Madison and other locations where 1,550 degree days (modified base 50°F) have accumulated, and will stay open until 2,100 degree days are surpassed.

TRUE ARMYWORM - Larvae are common in low numbers in corn and alfalfa. DATCP surveys indicate that infestation rates range from 1-8% and are still well below the 25% treatment threshold. However, these recent field observations emphasize the need for continued inspection of corn and lodged grains.

-- Krista Hamilton, DATCP Entomologist