Can biological products control Neonectria ditissima picking wound and leaf scar infections in apples?

Abstract

Neonectria ditissima is the causal agent of European canker in apple, and conidia infect wounds in apple trees. Several commercially available chemical fungicides and biological products (BPs) were tested for wound protection activity in three field experiments (2014-17). Freshly made wounds (rasp, picking, leaf and/or bud scar) were sprayed with the products at label rates. Wounds were challenge-inoculated with N. ditissima conidia after 24 hours and monitored monthly for lesion development. Only captan and copper oxide consistently protected wounds from infection and disease development in each experiment. The BPs tested in this study did not provide adequate wound protection when challenge-inoculated with N. ditissima at high concentration (>1000 spores/wound) so are not recommended for wound protection during harvest and leaf fall when disease pressure is high.