Induced emissions of apple fruit volatiles by the codling moth: changing patterns with different time periods after infestation and different larval instars

The changes in the emission of volatiles from mature apple fruits in respon se to larval feeding by the codling moth (Cydia pamonella) under laboratory conditions are reported. A time course experiment investigated the emissio n of volatiles throughout the period of larval development following infest ation. The volatiles consisted mainly of eaters, a few aldehydes, and the t erpene alpha -farnesene. Infested apples emitted the same compounds as heal thy apples. The quantities of volatiles released were much higher for infes ted as compared to healthy fruits for an initial three day period. Followin g this period there was a decrease in volatile emissions (days 6-9), eventu ally declining back to the levels emitted from healthy apples or below by 9 -21 days after infestation. In a separate experiment, the volatile emission s from healthy and artificially damaged fruits were compared to those from herbivore damaged fruits for each of the five larval instars of C. pomonell a. The results from the discriminant analysis indicate that the most effect ive induction of volatiles occurred when fruits were infested with first in star larvae. Induction by first instar larvae was generally higher than aft er infestation by later instars. and for must compounds it also exceeded th e emission from artificially damaged fruits. (C) 2001 Elsevier Science Ltd. All lights reserved.