EVALUATION OF COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) DEFOLIATION WITH CONCOMITANT EUROPEAN CORN-BORER (LEPIDOPTERA, PYRALIDAE) DAMAGE ON POTATO YIELD

The relationship between Irish potato, Solanum tuberosum L., yield and Colorado potato beetle, Leptinotarsa decemlineata (Say), defoliation has been established in many regions but rarely has been considered co incident damage by other pests. In eastern North Carolina, the Colorad o potato beetle and the European corn borer, Ostrinia nubilalis (Hubne r), attack potato each spring, and tile potential exists for reduced p otato yields caused by a combination of potato beetle and corn borer d amage. Yields from potatoes damaged by both pests were evaluated in sm all-plot experiments for 3 yr. Plant damage was achieved. by manipulat ing pest densities with insecticides and by augmenting plots with nota te beetles from nearby commercial fields. Yields were measured at the end of each growing season in late June to early July. Defoliation cau sed by Colorado potato beetle during bloom significantly reduced yield s of U.S. No. 1 tubers in 'Atlantic' each year, whereas European corn borer damage did not. Absence of an interaction effect between corn bo rer damage and defoliation on potato yield indicated that the yield/da mage relationship for each pest can be defined independently.