| Sclerotinia blight of peanut (Arachis hypogaea L.), caused by Sclerotinia minor (Jagger) Kohn, is an important disease in North Carolina and Virginia. Sclerotia are the main overwintering propagules of S. minor and serve as the primary source of inoculum for Sclerotinia blight. The effectiveness of the fungal mycoparasite Coniothyrium minitans, which is capable of colonizing sclerotia of Sclerotinia spp., was evaluated in a 5-year field study and in eight short-term field studies in northeastern North Carolina. Control of Sclerotinia blight was highest when C. minitans was applied for 3 consecutive years.;The integration of C. minitans with current peanut management practices is needed for successful biological control of Sclerotinia blight. Laboratory experiments evaluated the effects of nine pesticides commonly used in peanut production on mycelial growth, conidia germination, and mycoparasitic activity of C. minitans on sclerotia of S. minor. The commercial formulations of the fungicides azoxystrobin, chlorothalonil, fluazinam, pyraclostrobin, and tebuconazole, and the herbicide flumioxazin reduced mycelial growth and conidia germination of C. minitans. Eight of nine pesticides, azoxystrobin, chlorothalonil, fluazinam, pyraclostrobin, tebuconazole, diclosulam, flumioxazin, and pendimethalin applied to soil plates reduced but did not inhibit the mycoparasitic activity of C. minitans on sclerotia of S. minor. Temperature and moisture effects on mycoparasitism were also evaluated to determine optimum conditions for infection of sclerotia of S. minor by C. minitans. Optimum temperatures for infection of sclerotia of S. minor by C. minitans ranged from 14 to 22° C and soil moisture -0.33 to -1 kPa x 102. These results indicate that C. minitans should remain active throughout most of the year in North Carolina, except during the hot summer months of June, July and August. (Abstract shortened by UMI.)... |
