PLACEMENT AND APPLICATION RATE OF THE NEMATODE STEINERNEMA-CARPOCAPSAE (RHABDITIDA, STEINERNEMATIDAE) FOR SUPPRESSION OF THE WESTERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

Efficacy of the entomopathogenic nematode, Steinernema carpocapsae Wei ser (Mexican strain), as a control agent for the western corn rootworm , Diabrotica virgifera virgifera LeConte, was evaluated with nematode placement in three areas around the base of the maize plant and at fou r rates of application. Aqueous nematode suspensions were applied to t he soil surface when the rootworm larval population was predominately 2nd stage. Efficacy was evaluated on the basis of root damage and adul t emergence. The application of 100,000 or 200,000 nematodes within a 15 cm diameter circle centered on the base of the maize plant was most effective in reducing root damage and adult emergence. These applicat ion rates held root damage near the threshold for potential economic l oss (level 5, 1-9 scale) and adult emergence was reduced by 79-93%.