Biological Control of the Western Corn Rootworm (Coleoptera: Chrysomelidae) Using the Entomopathogenic Nematode,Steinernema carpocapsae

A series of eld trials evaluated the efcacy of the entomopathogenic nematode, Steinernema carpocapsae Weiser All strain for control of western corn rootworm, Diabrotica virgifera virgifera LeConte, larvae. Separate trials examined the effects of nematode application rate and timing on corn rootworm control in 1991. In the rate trial, S. carpocapsae (0, 10 4 , 10 5 , 10 6 , and 10 7 nematodes per 30.5 row-cm) was applied as the insect population entered the second instar. Nematode treatment signicantly reduced corn root injury and adult emergence. High application rates (10 6 and 10 7 nematodes per 30.5 row-cm) signicantly outperformed low rates (10 4 and 10 5 nematodes per 30.5 row-cm). Nematode treatment (500,000 S. carpocapsae per 30.5 row-cm) reduced root injury and adult emergence slightly in the timing trial; later applications (second, third instar) were numerically, but not signicantly, more effective than early (egg, rst instar) ones. In 1992, a factorial trial combined four application dates (egg; rst, second, third instar) and ve rates (0, 10 4 , 10 5 , 10 6 , 10 7 S. carpocapsae per 30.5 row-cm). Later applications (second, and particularly, third instar) were signicantly more effective than early (egg, rst instar) ones. Root injury and adult emergence in control and low rate (10 4 and 10 5 nematodes per 30.5 row-cm) plots signicantly exceeded that in high rate (10 6 and 10 7 nematodes per 30.5 row-cm) plots. Commercially acceptable root protection (root injury ratings below 3.0) was provided by 10 6 nematodes per 30.5 cm of row applied to third instars, and by 10 7 nematodes per 30.5 cm of row applied to second and third instars.