Submitted to: Canadian Society for Horticultural Science
Publication Type: Other
Publication Acceptance Date: May 19, 2003
Publication Date: N/A
Technical Abstract: The pear psylla is a serious insect pest of pear in North America and Europe. The insect has developed resistance to most of the pesticides employed for control and biological controls alone have rarely provided sufficient control for commercial production. The annual cost of chemical control exceeds U.S. $300 per acre. Cultivars with durable resistance would enhance the economic and environmental sustainability of pear production by reducing producer costs and pesticide use. The different species of pear psylla and their host apparently co-evolved in Europe. Early investigations of western European cultivars identified only a single moderately resistant cultivar. Pomologists and breeders have been collecting wild germplasm and landrace cultivars in order to identify diverse sources of resistance for use in the development of new psylla-resistant cultivars. Nine plant germplasm introductions of pear from Central Europe recently released from plant quarantine were evaluated for nymphal feeding inhibition, a primary mode of resistance known to be correlated with inhibition of egg-laying, and nymphal mortality/ reduced developmental rate. Five single-shoot budded trees were grown in the greenhouse without pesticides. The top two youngest fully expanded leaves were infested with ten 2nd and 3rd instar nymphs from a young laboratory colony. The number of surviving nymphs and the number of actively feeding nymphs was recorded after two days. Three cultivars from Yugoslavia, 'Karamanka', 'Jerisbasma', and 'Vodenjac', plus NY 10353 (a resistant control with wild pear ancestry) were significantly more resistant to nymphal feeding than the susceptible control, 'Bartlett'. These objective data confirm field observations made in Europe. These three Yugoslavian cultivars have relatively poor fruit quality, but increase the number of psylla-resistant genotypes available for breeding new pear cultivars suitable for North America.