Optimization and field-testing of synthetic sex attractants for two psyllid pests of pears (Hemiptera: Psyllidae)

Abstract

OBJECTIVES OVERVIEW Improve field activity of pheromone Evaluation of the seasonality of psylla reproduction Evaluate the seasonality of female attractiveness (pheromone production) Evaluate seasonality of male response to synthetic pheromone components Develop practical use for pheromone Test psylla trapping by synthetic pheromone impregnated in rubber septa (provided by J. Millar, cooperator in USA). Test a sprayable formulation of pheromone developed by D. Horton (USA cooperator) SIGNIFICANT FINDINGS No consistent seasonality in female attractiveness was observed. Female attractiveness was observed in winter forms in the end December and in May-June in summer forms. C. bidenshas a very distinct but short period of low mating rate, that is associated with low ovarian development. This short period of low ovarian development and low mating rate cannot be considered as a reproductive diapause. Ovarian development is inhibited by short day photoperiod especially in presence of low temperatures. Male attraction to individual synthetic putative pheromone components is not strong and fluctuates seasonally. While 7MeC27was attractive to males of the winter form, it was not attractive to the summer forms in the beginning of the summer. These data are in accordance with differences in cuticular profiles of winter and summer attractive females vs non attractive ones. Cuticular profile of females shows significant seasonality and difference according to their attractiveness to males especially in summer time. Differences between attractive and non-attractive females is based on several compounds . Female attraciveness in summer and winter is apparently based on a different combination of chemical cues, but 7meC27 is one of the common components to both mixtures. These two last findings are likely to be the main reason for our failure to have consistent success in trapping C. bidensin the field. It seems that a sprayable formulation of pheromone on the pear is better way of pheromone application to attract psyllid then the impregnated rubber septa, but additional trials are needed.