Syrphid releasing vs Eriosoma lanigerum: preliminary results

In the last few years, one of the most worrying pests for apple production in the Southern Alps is woolly apple aphid (WAA), Eriosoma lanigerum Hausmann. It causes hypertrophy and tissue ruptures in roots and shoots of apple trees. This can reduce sap flow, vigour, tree productivity and fruit quality. Since the challenge facing agriculture in the coming years is to produce a good yield of healthy food using improved environmentally friendly practices, enhancing biological pest control is crucial. A great control of the WAA population is made by the parasitoid Aphelinus mali Haldeman but only for a short period of the season. Syrphidae is known to have high predatory potential on the population of aphids in orchards, i.e., Ephisyrphus balteatus De Geer is one of the most effective biocontrol agents against aphids in apple orchards. For these reasons, the ability of Syrphidae in controlling the population of WAA in apple orchards of Trentino (North Italy) was evaluated during the season 2023. The trial was carried out in three potentially high-infested orchards: two orchards were treated with beneficial insects, and one was non-treated (control). The orchards were organic managed, cultivated with Golden Delicious variety on M9 rootstock. In the treated orchards, pupae of E. balteatus and Sphaerophoria ruepellii Wiedemann of the Koppert B.V. company were released in March. WAA migration on trees and A. mali population were monitored on sticky traps during the season. WAA infestation was assessed by visual observations of 50 marked shoots in each orchard from April to August, as well as the presence of predators. Preliminary results of one-year trial showed that Syrphidae release alone was not successful in reducing WAA infestation, but a positive effect could be observed as after one month from the release, Syrphidae abundance on WAA colonies was much higher in the treated orchards