Codling moth uses yeast to digest fruit

Codling moth (Cydia pomonella) is a major pest insect of apples worldwide; the larvae mine and destroy the fruit.

Chemical ecologists at SLU (the Swedish University of Agricultural Sciences),yeast molecular biologists at Lund University and entomologists from USDA (United States Department of Agriculture) have now shown that the larvae associate with a yeast (Metschnikowia), and that this yeast is an essential part of the larval diet.

Yeast also protects the larval galleries against fungal infestations, which increases larval survival.

Female codling moths are attracted to a blend of odours from yeast and apple for egg-laying. This reflects the evolution of odour communication between insects, plants and microorganisms.

The phylogenetically ancient part of the insect olfactory system, which originated during marine life, is dedicated to microbial cues. The transition to terrestrial life made it necessary for the insects to also develop sensors for green plant odours.

Attraction to a combination of microbial odours and green plant odours facilitates host plant switches and evolution in plant feeding insects.