PETAL BLIGHT, A NEW DISEASE OF THE CANNA ’PFITZER’S DWARF’

A severe petal blight was found affecting the canna ’Pfitzers Dwarf’ at Ottawa in 1959. The principal cause proved to be a pathogenic strain of an Alternarai of the tenuis type. Petal infection readily occurred from 5° to 30 °C. but lesions developed most rapidly at 25 °C The fungus also infected wounded leaves of canna, but it caused little decay. Myrothecium verrucaria (Alb. & Schw.) Ditmar ex Fr., isolated once from a diseased petal, could infect petals but it caused less rapid decay than the Alternaria.