Early Cutting of Corn as a Method of Reducing Populations of Corn Rootworms12

The effect of removing corn at different dates on corn rootworm populations was evaluated for 2 years at Yankton, South Dakota. Early cutting caused some mortality and resulted in wide dispersal of the western corn rootworm, Diabrotica virgitera LeConte, and the northern corn rootworm, D. longicornis. (Say). Fall counts of eggs were not reliable indicators of the amount of damage the following summer. Yield was not a good indicator of larval populations because of other influencing factors such as fertility or rainfall. The 2 most effective methods of estimating populations of corn rootwromproved to be counts of larvae and larval damage, when corn was removed before Sept. 1, popubtions of corn rootwrom the next year were below economic proportions. Thus, farmers who cut their corn before Sept. 1 could expect little damage from corn rootworms the following year and might not have to apply insecticides.