Characterization and Chemistry of Sexual Communication in Two Psyllid Pests of Pears (Homoptera: Psyllidae)

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Pear-feeding psyllids in the genus Cacopsylla (Hemiptera: Psyllidae) are among the most important arthropod pests of pears worldwide. These pests are exceedingly difficult to control, and new management tools are needed. Sex attractantpheromones have been used in IPM programs for pests of pome fruits (especially Lepidoptera), but not as yet for pest Hemiptera. Results of the current project showed that males of two psyllid pests of pears, Cacopsylla bidens (Israel) and Cacopsylla pyricola (North America), use volatile or semi-volatile compounds to locate female psyllids for mating. For both species, the attractants can be collected from the cuticle of females by washing live female psyllids with an appropriate solvent. Analysis of these washes by gas chromatography – mass spectrometry led to the following discoveries: Psyllid cuticles contain a mix of hydrocarbons, straight chain and branched alkanes, and long chain aldehydes The two species have different chemical profiles Chemical profiles change seasonally and with reproductive status Chemical profiles differ between male and reproductive female psyllids Several specific compounds found to be more abundant in attractive females than males were identified and synthesized. Behavioral assays (olfactometer) were then used to determine whether these compounds were attractive to males. Two compounds showed promise as attractants for male psyllids: 7-methylheptacosane (C. bidens) and 13-methylheptacosane (C. pyricola and C. bidens). These are the first sex attractantpheromones identified for any psyllid species. Field tests showed that the chemicals could be used to attract males under orchard conditions, but that effectiveness in the field appeared to be seasonally variable. Future research plans include: (a) test mixtures of compounds; (b) explore seasonality in field response to compounds; (c) determine whether chirality of the two compounds affects their attractiveness; and (d) compare different types of traps and release devices to optimize lure performance.