MORTALITY AND DEVELOPMENT OF PEAR PSYLLA NYMPHS ON EAST EUROPEAN PEAR GERMPLASM

Abstract

Four genotypes of pear (Pyrus spp.) of East European origin, a susceptible control, `Bartlett' (P. communis L.), and a moderately resistant control, NY 10352 (P. ussuriensis Maxim. × P. communis B C1 hybrid), were artificially infested with pear psylla (Cacopsyll a pyricol a Foerster) nymphs in the laboratory. Ten neonate first instars were placed on each of the two youngest leaves of four small trees per genotype. On PI 506381 and PI 506382, wild seedlings of P. nivalis Jacq., all nymphs died within 5 days. Mortality and development of nymphs on PI 502173, a wild P. communis seedling, was similar to that observed on `Bartlett', with 43% and 45% of the nymphs surviving to adulthood, respectively. On `Karamanlika' (PI 502165) and NY 10352, 15% of the nymphs developed into adults. Increased mortality and delayed development of nymphs was associated with feeding inhibition. The mode of host plant resistance to pear psylla nymphs in these accessions of East European pear is, therefore, similar to that previously characterized for NY 10352, in which the resistance is derived from germplasm of East Asian origin.