Control of Anthonomus spp. weevils in IPM pome fruit orchards

Since the withdrawal of broad spectrum insecticides like carbamates and organophosphates and the restricted use of neonicotinoids, weevils have become an increasing problem in pome fruit in Belgium. In particular, the apple blossom weevil Anthonomus pomorum and the pear bud weevil Anthonomus pyri (syn. A. cinctus or A. piri), that used to be secondary pests, have developed into important pests for many apple and pear growers, respectively. Recently, also the pear blossom weevil Anthonomus spilotus was found to be present in several pear orchards in Belgium, causing considerable damage. Here we present an overview of recent monitoring data, field and laboratory trials, executed in the Belgian fruit growing area near Sint-Truiden. Laboratory trials on A. pyri indicated a high direct contact activity as well as a high indirect residual contact activity of the neonicotinoid insecticides thiacloprid and acetamiprid, while the anthranilic diamide insecticide cyantraniliprole reached only good control activity after exposure of the A. pyri weevils to spray residue on leaves. In a field trial, application of thiacloprid and cyantraliprole targeting the active A. pyri weevils in autumn also resulted in very high control efficacies, leaving opportunities for a successful combination of those insecticides with biological control by the parasitoid Scambus pomorum. This opens perspectives for control strategies in line with sustainable integrated pest management (IPM) principles.