Protection of budding wounds in apple nursery trees from European canker

Abstract

The fungus Neonectria ditissima can cause European canker in apple nursery trees. In this study, ten treatments of 'EMLA 9' rootstocks budded with 'Royal Gala' were examined, 5 and 15 months after budding and inoculation with conidia of N. ditissima (2×105 conidia/ml). Treatments included combinations of five budding tapes, two budding methods and three fungicidal treatments. Fifteen months after inoculation, all T-budded trees had died. Chipbudded trees inoculated after tying with either Flexiband type C or plastic pre-cut strips displayed significantly more canker (21% and 22%, respectively) than those tied with Buddy tape (11%, P<0.001). Of the uninoculated trees, 9% displayed canker symptoms, because either the budding wounds were infected by natural inoculum, or the infection was present in the scion or rootstock before budding. Treating buds with tebuconazole/carbendazim reduced canker symptoms significantly (2%, P<0.001). Calcium hydroxide also reduced canker symptoms (5%). Pyraclostrobin/boscalid did not reduce canker incidence.