Codling moth (Cydia pomonella L.) egg-laying behaviour on two Malus sp. preferred and non preferred for egg-laying and leaf surface metabolite signals

Abstract: Cydia pomonella (C. pomonella) is the main pest of Malus domestica (M. d.). Malus floribunda (M. f.) which is used in orchards to cross pollinate trees, shows no C. pomonella damage. We observed on single trees without any alternative that 60% of females may lay eggs on M. d. (41 eggs) vs. 0% on M. f. After collecting and analyzing, by gas chromatography, leaf surface metabolites, we were able to test the known active metabolite pattern on females to confirm the tree observations. Acceptance and egg-laying was reduced by the M. f. metabolite pattern. The gravid female behavior was observed on trees in no-choice controlled conditions. On both Malus. sp. females preferred to land on the upper side of corymb leaves and on the fruits. Then females generally remained on the site where they had landed. The behavioural difference to both Malus sp. was observed at the stage of ovipositor scanning, which was linked to egg-laying. Scanning was dramatically reduced on M. f. and the locomotion speed was lower. Host and non-host characters belonged to the egg-laying stage and non volatile metabolites.