Colorado Potato Beetle (Coleoptera: Chrysomelidae): Expression of Resistance in Solanum berthaultii and Interspecific Potato Hybrids

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Abstract
A wild potato species, Solanum berthaultii Hawkes, and its interspecific hybrids with the commercial potato, S. tuberosum L., were evaluated for resistance to the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) in field and laboratory studies in New York. Field-collected summer adults produced nearly 3-fold more eggs on S. tuberosum cv. Katahdin than on S. berthaultii over a 7-day period. Egg masses laid on ‘Katahdin’ were 61% larger than those laid on S. berthaultii. In field cage plots of S. berthaultii, CPB larval development was retarded and very few larvae survived to adulthood. Densities of overwintered CPB adults and defoliation levels were significantly reduced on S. berthaultii compared with S. tuberosum in open field studies. A hybrid family had intermediate levels of defoliation and adult CPB densities. During the second CPB larval generation, densities of small (first and second instars) and large (third and fourth instars) larvae were reduced 90 and 87%, respectively, on the hybrid family and 96 and 97%, respectively, on S. berthaultii compared with cpa densities on S. tuberosum. In other field studies, three to four applications of insecticides timed by use of action thresholds were sufficient to maintain acceptably low levels of defoliation on three hybrid families, one application was needed on S. berthaultii, but three applications failed to control CPB on S. tuberosum.