Susceptibility of grapevine pruning wounds and symptom development in response to infection by Phaeoacremonium aleophilum and Phaeomoniella chlamydospora

Fresh to 10-month-old pruning wounds on grapevine cvs. Thompson Seedless and Cabernet Sauvignon were inoculated with Phaeoacremonium aleophilum or Phaeomoniella chlamydospora at approximately 1 X 10(6) spores/ml. Successful infection was determined by isolation of the pathogen from necrotic margins of cankers or from vascular discoloration assessed 4 months after each inoculation date. Disease incidence decreased as the length of time between pruning and inoculation increased; however, wounds remained susceptible for up to 4 months. Vascular discoloration was significantly less extensive in the noninoculated control than in inoculated spurs. Reduction of shoot length in both cultivars varied depending on pruning wound age at the time of inoculation. In a separate study, inoculation of fresh pruning wounds of Cabernet Sauvignon resulted in successful infection regardless of the time of pruning from February to December.