Department of Plant Pathology

There are no therapeutic treatments for canker diseases of grapevine. These diseases can be prevented, however, by protecting dormant pruning wounds from airborne inoculum. A single fungicide application after pruning reduced canker incidence in 159/160 cases and canker severity in 16/16 cases. Thiophanate-methyl was most effective against Lasiodiplodia theobromae and myclobutanil was effective against Eutypa lata. Both fungicides were effective against Phaeoacremonium aleophilum and Phaeomoniella chlamydospora. Pruning wounds were found to be most susceptible to canker pathogens in December and least susceptible in March, and late or double pruning was shown to augment fungicide effectiveness in reducing canker disease incidence. Pruning wound susceptibility to canker pathogens was found to decrease significantly three weeks after pruning. The practical implications of these results are discussed.