Incidence of apple fruit and leaf surface metabolites on Cydia pomonella oviposition

Water soluble metabolites identified from surfaces of apple tree fruit and leaf stimulate oviposition in Cydia pomonella L. The effects of two artificial blends of primary metabolites representing fruit and leaf surfaces, respectively, and of components within the blends were examined on egg‐laying after two time periods: 3 min and 25 min of darkness. An artificial mixture of six metabolites, viz., three sugar alcohols (sorbitol, quebrachitol, and m yo ‐inositol) and three sugars (glucose, fructose, and sucrose) did stimulate egg‐laying. Fructose, sorbitol, and myo ‐inositol are important components of the stimulatory blend. Contact durations may induce variations in egg‐laying responses. After 3 min of darkness, there were no differences in numbers of females laying eggs nor in the numbers of eggs laid on cloths treated with the complete blends and the controls. There were, however, clear effects of groups of compounds and of individual compounds. Reduced blends without sugars and sugar alcohols were in many cases significantly less stimulatory than the complete blends and the controls. After 25 min of darkness, the proportions of females laying eggs as well as the numbers of eggs were higher after treatment with the complete blends than on the controls. The proportions of females laying eggs on cloths treated with the reduced blends were rather similar to the controls, whereas there were still significant effects on the numbers of eggs laid after treatment with reduced blends derived from fruits but not from leaves.