Use of sex pheromones and plant volatile compounds for environmentally safe pest control in pome fruit orchards

The objective is to develop new control methods against insects infesting fruits. The strategy is to alter the insects' behaviour by using their own chemical communication system. The methods should be efficient as well as environmentally safe.

Background. New legislation limits the use of chemical insecticides in both the European Union and in the US. The number of insecticides for control of the codling moth (Cydia pomonella) and other pests on fruits is now limited. At the same time, the resistance of insects to the insecticides in use increases. The development of new control methods is necessary for both successful fruit production and for environmental reasons.

Pheromones. Mating disruption or confusion is today a commercially available biological control strategy. Synthetic mimics of the female sex pheromone are released in the orchard making it difficult for the males to find the females, because the female odour is present everywhere. One of the goals is to make the disruption method more efficient against the codling moth. This work is accomplished by identifying new pheromone components and by investigating their importance in behavioural tests and in large-scale suppression experiments. Alternative methods to use pheromones for population control are mass trapping and attract & kill. In the latter method the males are attracted to pheromone baits combined with a poison. The poison might be a chemical insecticide or an insect pathogen that kills the attracted males. This method requires much less toxic substance than conventional spraying and, in addition, the poison can be removed after the season.

Plant volatiles. One drawback by using pheromones is that only males are affected and that mated females can immigrate from surrounding untreated areas and oviposit in the pheromone-treated orchard. The codling moth and some closely related species oviposit on or near the fruits of a few closely related plant species. The egg laying is to a large extent determined by plant volatiles. Chemical analysis of volatile substances from apple, combined with the antennal response of females on these compounds show that a few key compounds are essential for the female behaviour.

Application. A combination of mating disruption of males with catch of ovipositing females can become a very efficient control strategy, and a sustainable alternative to chemical insecticides.

Place of research: Chemical ecology, Department of plant sciences (in Swedish), Swedish University of Agricultural Sciences, Alnarp

Participating scientists: Peter Witzgall (project leader), Lena Ansebo, Marie Bengtsson, Anna-Carin Bäckman, Miryan Coracini, Jan Löfqvist†, Per Nilsson, Marco Tasin

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