Abstract:

The aims are to clarify the effect of the new fungicide boscalid on the biological activity of Sclerotinia sclerotiorum, and provide a scientific basis for its promotion and application. In this research, we used the hyphae, spores and sclerotia as test samples. Bioassay method was used to confirm the effect of boscalid on mycelial growth, spore germination and sclerotia formation of Sclerotinia sclerotiorum. The results showed that the mycelial growth rate of Sclerotinia sclerotiorum treated with boscalid was inhibited; the EC₅₀ was 0.2152 μg/mL. With the increase of germicide concentration, the mycelial growth of Sclerotinia sclerotiorum decreased significantly. When the concentration was 16.667μg/mL, the inhibition rate of sclerotia formation of Sclerotinia sclerotiorum reached 84.62%, and the inhibition rate of total dry weight of sclerotia formation of Sclerotinia sclerotiorum reached 61.07%. The result of spore germination test showed that the germination of ascospores was inhibited after being treated with boscalid, and the EC₅₀ was 0.056 μg/mL. The inhibition rate of spore germ tube elongation reached 78.15% at the concentration of 0.267 μg/mL. The boscalid not only inhibits the mycelial growth of Sclerotinia sclerotiorum, but also reduces the invasion of ascospores, and prevents the germ cells formed by the germination of ascospores from infecting the plant tissues continuously, which effectively reduces the residual amount of sclerotia in field soil. It has a very broad prospect for the prevention and treatment of sunflower sclerotinia, and can be used as a rotation agent for controlling sunflower sclerotinia in field.

Key words: Sclerotinia Rot of Sunflower, Boscalid, Sclerotinia Sclerotiorum, Hyphal Growth, Spore Germination