PHOTOSYNTHETIC AND GLYCOALKALOID RESPONSES OF POTATO (Solanum tuberosum L.) TO COLORADO POTATO BEETLE (Leptinotarsa decemlineata Say) DEFOLIATION

Photosynthetic and glycoalkaloid responses of potatoes (Solanum tuberosum L.) to varying levels of Colorado potato beetle (Leptinotarsa decemlineata Say) and manual defoliation were measured on 'Cal Red' and 'Russet Burbank' plants. No alteration in photosynthesis was observed on the remaining tissue of an injured leaf for Cal Red and Russet Burbank leaves defoliated by larval Colorado potato beetles nor for Russet Burbank leaves defoliated by adult Colorado potato beetles. No significant differences were observed between actual Colorado potato beetle and manual defoliation for both varieties. In both of the whole-plant defoliation studies, defoliation level consistently did not result in increased or decreased gas exchange parameters of individual leaves compared to undefoliated controls. There was no evidence of delayed leaf senescence in defoliated treatments. Plants defoliated by Colorado potato beetles had a significantly greater production of glycoalkaloids than in control and in manually defoliated plants for both skin and inner tissue.