Susceptibility of evergreen azalea cultivars to anthracnose caused by Colletotrichum acutatum

Abstract

Colletotrichum acutatum is the causal agent of anthracnose on azalea (Rhododendron azalea). This disease was observed in Fall 2002 on 'Palestrina' azalea in Italy. Severe outbreaks of this disease were recently observed on several cultivars of azalea grown in nurseries located in the Verbano-Cusio-Ossola Province in the Piedmont region of northern Italy. Information on susceptibility to C. acutatum among azalea cultivars currently grown in Italy was unavailable. Artificial inoculations were performed to evaluate the susceptibility of 70 evergreen azalea cultivars produced in the Lake Maggiore area. Sixty of the cultivars evaluated failed to develop disease symptoms and were considered resistant to C. acutatum. Symptomatic cultivars were placed into three susceptibility classes. The cultivars Addy Wery, Fior di Pesco Cavadini, Geisha Orangerot, Kermesina, Orion, Palestrina, and Snow developed severe anthracnose symptoms. The cultivars Conversation Piece, Eikan, and Martha Hitchcock showed moderate susceptibility.