Corn Rootworm Egg Hatch Estimates

Originally Submitted: June 24, 2021

Corn rootworms overwinter in the soil as eggs and hatch in the spring when enough soil degree days have been accumulated (soil base 52 degrees Fahrenheit). At 684–767 soil degree days, approximately 50% of the rootworm egg hatch occurs. Based on soil degree day accumulations, most of South Dakota has reached 50% corn rootworm egg hatch (Table 1). We recommend scouting for corn rootworm injury in corn fields 10–14 days after 767 soil degree days have been reached. For many locations, that will be next week.

As a reminder, all corn fields should be scouted for corn rootworm injury. Extra emphasis should be placed on fields with a history of corn-corn rotations or with Bacillus thuringiensis (Bt) performance issues. Scouting shortly after peak egg hatch provides a great opportunity to observe fresh injury on the roots.

Predicting Activity With Degree Days