Explanation of the failure of a commercial scale application of benomyl to protect pruned apricot trees against Eutypa dieback disease

Abstract

Application of 0.56 kg benomyl per ha by turbomist sprayer to pruned apricot trees resulted in a slight reduction (P<0.05) in their susceptibility to infection from Eutypa armeniacae ascospores introduced on day 0, but no significant reduction occurred when spores were introduced three or more days later. A majority of the pruned sites yielded less than 3 µg per cm2 of extractable MBC 1 hour after spraying. This finding explains the discrepancy between the high level of protection obtained when the sapwood is saturated by a liberal application of benomyl to each pruned site and the lack of protection in other experiments where the chemical was applied to entire trees by conventional commercial spraying methods.