EPIDEMIOLOGY AND CONTROL OF ASCOCHYTA PINODES ON FIELD PEAS IN CANADA

Blight, caused by Mycosphaerella pinodes, is now epiphytotic and Ascochyta pinodes is the principal pathogen found in Canadian field pea seed. Ascochyta pisi, cause of leaf and pod spot of peas and formerly the principal seed-borne pathogen, is now seldom found. Reasons for this situation are discussed. Although infection by A. pinodes, from the seed to seedling stage, took place over a temperature range of 10 to 30[degree]C, the optimum range for infection was 15 to 18[degree]C. The symptoms produced at the different temperatures are described. Thiram 75, Orthocide 75, Panogen 15 and Spergon as seed treatments were effective in controlling the organism in sand, sandy loam and sterilized sandy loam. Thiram 75 and Orthocide 75 were equal in effectiveness and significantly better than Panogen 15 or Spergon.