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May
21
Posted by:
WCM Staff
5/21/2008 5:08 PM
With the relatively cool spring temperatures this year, insect development degree-days have been accumulating about 1-2 weeks slower than a typical spring. Corn planting is finishing up in Wisconsin, and growers and consultants will begin to ask about corn rootworm egg hatch and expected time frame of first through third larval instar corn rootworm feeding on corn roots.
Corn Rootworm Egg Hatch Update for Wisconsin
Eileen Cullen, Field Crop Extension Entomologist
With the relatively cool spring temperatures this year, insect development degree-days have been accumulating about 1-2 weeks slower than a typical spring. Figure 1 shows the current “hatch map” for western corn rootworm overwintered eggs in the soil. Corn planting is finishing up in Wisconsin, and growers and consultants will begin to ask about corn rootworm egg hatch and expected time frame of first through third larval instar corn rootworm feeding on corn roots.
Western and northern corn rootworms overwinter as eggs in the soil. Corn rootworm begins development at 44F and hatches from overwintered eggs in early to mid-June at 800 degree days. One generation occurs per year in Wisconsin and the North Central Region. Larvae pass through three instars as they feed on corn roots. Peak feeding occurs for several weeks after hatching (between 1300-1700 degree days) and pupation occurs in mid-July. Adults emerge 5-10 days after pupation. Emergence is observed from mid-July to mid-August between 1800-2200 degree days. Egg laying begins two weeks after adult emergence and adults remain active until the first killing frost. Western corn rootworm generally completes development 4-5 days before NCR.
This spring, ZedX, Inc. is providing our UW Madison Extension field crop entomology program with statewide soil temperature updates and estimated corn rootworm hatch and larval development progress. ZedX, Inc. provides data and decision support tools to the agricultural sector, specializing in weather data and crop pest phenology models http://www.zedxinc.com/index.php.
Figure 1. Western corn rootworm overwintered egg hatch map. May 22, 2008.
Figure 1, current through May 22nd shows western corn rootworm egg hatch has not yet begun in WI. Western corn rootworm is the predominant species in most of WI. While northern corn rootworms also occur in WI, the western corn rootworm hatch map can be used for a state estimate of corn rootworm overwintered egg hatch and larval development (western and northern). Southern states in the Corn Belt are starting to record 1st instar development as evidenced by the light brown coloration beginning to appear at the bottom of the regional map in Figure 1.
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