13 PEAR SPECIES AND CULTIVARS EVALUATED FOR RESISTANCE TO CACOPSYLLA-PYRI (HOMOPTERA, PSYLLIDAE)

Thirteen pear, Pyrus spp., cultivars were evaluated under field and la boratory conditions for resistance to Cacopsylla pyri (L.). In field s tudies, population growth was quantified over a 1-mo period of develop ment. In the laboratory, the mode of host resistance was investigated by estimating oviposition and antibiosis. One cultivar and 3 pear spec ies were found to be resistant to pear psylla ('Hosui', P. betulaefoli a, P. pyrifolia, and P. ussuriensis); the remaining ones may be classi fied as susceptible (Doyennee du Comice, 'Williams', 'General Leclerc' , and 'Moonglow'). Antibiosis was a main factor determining resistance in the test pears, and preference for oviposition was involved to a m uch lesser degree.