Control of Eriosoma lanigerum with a microbial insecticide based on Beauveria bassiana strain ATCC74040

Abstract: The effectiveness of repeated applications of Beauveria bassiana strain ATCC 74040 (Naturalis®) against spring infestations of the woolly apple aphid, Eriosoma lanigerum, on apple was evaluated in three trials conducted over several years (2019-2021) in Northern Italy. An additional trial, carried out in 2021, aimed at verifying the efficacy of the entomopathogenic fungus against re-infestations in late summer-autumn. The percentage of infested shoots, the number of active colonies per shoot and the size of the active colonies on shoots were assessed. At the different tested rates (1, 2 and 3 l/ha) and time intervals between subsequent applications (1 or 2 weeks), the microorganism gave efficacy values in reducing spring infestations in case of medium-low pest pressure ranging from 56 to 97 %, statistically comparable to those of the reference strategy (61-100 %), while with very high pest pressure (trial conducted in 2021 on Fuji covered with hail net), its effectiveness was lower (23-54 % vs. 57-74 %). The effectiveness of the entomopathogen in reducing re-infestations in autumn, instead, was slightly higher than that of the synthetic reference insecticide (25-71 % vs. 22-46 %). The microbial insecticide constitutes an additional valuable tool to be included in the strategies for the control of this dangerous pest.