Net enclosures disrupt codling moth dispersal not establishment

Abstract

Apple growers have pursued the use of exclusion netting to reduce pesticide inputs and maintain control of codling moth. It is uncertain if these nets provide a physical or behavioural behaviour, and if they prevent codling moth establishment. To address this, we conducted field trials testing the ability of commercial netting to exclude codling moth using small (3 trees) and large (48 trees) cages. Experiments were conducted to evaluate both the permeability by releasing marked sterile moths either inside or outside the small cages, and the establishment of wild codling moth in the large cages. Results from the small cage study showed that netting reduced codling moth movement out of the netted plots, but virtually prevented codling moth dispersal into the plots. Codling moth capture inside the large cage plots was significantly less than in uncaged plots, but no differences were found in codling moth damage at harvest. These results indicate that the netting is physically permeable to codling moth adults; however, it acts as a behavioural barrier to moth immigration. These outcomes agree with existing literature that net enclosures can provide a non-insecticidal tool to improve codling moth management, although it may not be a stand-alone technique.