INFLUENCE OF HERBICIDES ON THE CARPOGENIC GERMINATION OF SCLEROTINIA-SCLEROTIORUM SCLEROTIA

We investigated the influence on carpogenic germination of Sclerotinia sclerotiorum sclerotia of thirty-one registered herbicides commonly used in production of cereals, oilseeds, pulse, potato, and sugarbeets in southern Alberta, and of two unregistered herbicides. Compared to the untreated controls, none of the herbicides showed any stimulatory or inhibitory influence on the carpogenic germination of sclerotia, when incorporated in soil at the recommended field rates. These herbicides had little influence on the differentiation and development of apothecia-except for the triazine herbicides simazine and atrazine, which induced formation of secondary stipes on the primary stipes. Simazine caused the formation of cockscomb-like apothecia containing very few asci and ascospores, and atrazine caused balls of mycelia without asci to form on the tips of stipes. Abnormal apothecial morphogenesis was induced by simazine and atrazine at 25% to 50% of the recommended field rate (1500 g/ha).