Christelle Guédot, David R. Horton, and Peter J. Landolt

USDA-ARS Yakima Agricultural Research Laboratory, Konnowac Pass Road, Wapato, WA

Cacopsylla pyricola has been a pest of pear trees in the western U.S. for several decades. Cacopsylla pyricola is multivoltine and seasonally dimorphic, with a dark overwintering adult and a small, light-colored summerform. This study addresses the chemical ecology of pear psylla C. pyricola in relation to mate location with a Y-tube olfactometer bioassay. Summerform males were attracted by summerform females on pear seedlings (64%) compare to uninfested pear seedlings (36%). Post-diapause winterform males showed similar attraction towards female infested pear shoots (68% vs. 32%). These results strongly support the hypothesis that C. pyricola females of either morphotype attract males with volatile chemicals. Several factors, such as insect age, ovarian maturation (diapause status), presence of host plant, mating status, and circadian rhythm could affect pheromone production and perception. Virgin summerform males showed a preference for 8-10 day old virgin females (76%) versus 2-4 day old virgin females (24%). The presence of the host plant with winterform females was addressed and showed that males are attracted by females even in the absence of the host plant. Collection of volatile chemical attractants emitted by pear psylla females is underway.