Studies on the survival of Mycosphaerella pinodes and Ascochyta pisi

SUMMARY Laboratory and field experiments on two pea‐pod and leaf‐spot pathogens, Mycosphaerella pinodes and Ascochyta pisi, have indicated that the former species may survive overwinter in soil whether introduced as pycnidiospores, mycelium, chlamydospores or sclerotia. The survival of pycnidiospores appears to be due at least in part to their transformation into chlamydospores in the soil. A. pisi was much less successful in soil; the mycelium inoculum survived, somewhat sporadically, and spore viability was reduced, while the total number of spores declined markedly. Investigations on the competitive saprophytic ability of these pathogens showed that by the agar plate method M. pinodes could be classed as a moderately successful saprophyte, though the Butler and Park methods indicated only intermediate and poor success respectively. A. pisi was adjudged a poor saprophyte by all three methods. Saprophytic growth and survival in soil of both fungi was generally better at 2 °C than at 15 °C.