Factors affecting germination of sclerotia of Sclerotinia sclerotiorum from peas

Application of nitrolim, which contains 57% calcium cyanamide, to the soil surface completely inhibited germination of sclerotia of Sclerotinia sclerotiorum, whether buried or placed on the soil surface, over a period of at least 20 weeks at 20°C, whereas most sclerotia on untreated soil germinated within 5 weeks, producing apothecia 2–6 weeks later. Temperature markedly influenced the germination rate of sclerotia. On untreated soil, sclerotia failed to germinate at 10° after 4 weeks, and at 15° only one-third had germinated. Hydrogen cyan-amide was a less effective inhibitor of germination than nitrolim. Benlate and benzotriazole inhibited germination of sclerotia over a period of at least 20 weeks at 20° but parabanic acid had no effect. Initial inhibition by maleic acid hydrazide was followed by normal germination and the formation of apothecia.