Influences of insecticides and herbicides on the growth of the biocontrol fungus Coniothyrium minitans Campbell

The colony-diameter methods recommended by FAO were used to evaluate the toxicity of eight insecticides, four her bicides, three plant-growth regulators and one antibiotic to Coniothyrium minitans Campbell. Results show that among insecticides, cypermethrin, abamectin, chlorpyrfos and dichlorovos are most toxic to the biocontrol agent (EC₅₀＞MRAR, Maximal recommended application rate), followed by phoxim and omethoate, however, imidacloprid and methomyl hardly have inhibitory effects. All herbicides tested can strongly inhibit mycelial growth and their EC₅₀ values are significantly lower than the MRAR. Under the recommended application rates, all plant-growth regulators tested are safe to the fungus. Although streptomycin sulfate has some inhibiting effects on the growth of C. minitans, its EC₅₀ value is higher than the MRAR. It is suggested that the plant-growth regulators, such as naphthaleneacetic acid, gibberellic acid, brassinolide, and insecticides, such as imidacloprid and methomyl may be safely used in the fields using C. minitans to control sclerotinia disease, but herbicide lactofen, haloxyfop-R-Methyl, paraquat and glyphosate should be restrictedly used.