Control of the Western Spotted Cucumber Beetle Using a Predaceous Nematode

The corn rootworm (Diabrotica spp.) causes extensive damage to corn (Zea mays L.) as well as other crops throughout the United States. Research has shown the Steinemema carpocapsae nematode has potential as a biocontrol agent for control of the corn rootworm. An experiment was conducted at California Polytechnic State University, San Luis Obispo, in July 1990. The objectives of this research were to determine the efficacy of field applications of entomogenous nematodes and to compare the use of entomogenous nematodes with chemical applications for control of the corn rootworm. Treatments consisted of a nematode solution applied at a rate of 1 billion nematodes/acre; chlorpyrifos granular insecticide applied at 6.6 pounds/acre; a combination of nematodes and chlorpyrifos; and an untreated control. Data collected included beetle counts, root ratings, and corn ear percent moisture. A standard Galleria mellonella bioassay was conducted to determine the persistence of the nematodes in the field. Corn root damage ratings indicated the control treatment had significantly more rootworm damage than the other treatments; the nematode, chlorpyrifos, and combination treatments were not significantly different from each other. Additionally, bioassay results indicated the nematodes persisted in the field for at least 5 wk. From these results, it appears the Steinernema carpocapsae treatment was as effective as the chlorpyrifos treatment in preventing corn rootworm damage.