THE EFFECT OF CHEMICAL PESTICIDES ON THE INFECTION OF SCLEROTIA OF SCLEROTINIA-MINOR BY THE BIOCONTROL AGENT SPORIDESMIUM-SCLEROTIVORUM

Pesticides were evaluated in vitro and in soil for toxicity to Sporidesmium sclerotivorum. Of the 46 pesticides evaluated in vitro, five fungicides (benomyl, captafol, chlorothalonil, thiabendazole, and thiophanate-methyl) and one herbicide (naptalam + dinoseb) were highly toxic to the biocontrol agent at 1-mu-g/ml in poison agar assays. Only three fungicides (anilazine, pentachloronitrobenzene, and thiram) were moderately toxic at 10-mu-g/ml. The remaining 37 pesticides were either slightly toxic (100-mu-g/ml) or less. In soil, chlorothalonil was the most toxic pesticide. This fungicide prevented the infection of sclerotia of Sclerotinia minor in soil by S. sclerotivorum at 10-mu-g/g of soil. Five fungicides were further evaluated in soil columns. None of the fungicides were toxic to the biocontrol agent in soil at concentrations likely to be encountered in the field. Apparently, pesticides can be used in conjunction with S. sclerotivorum in an integrated approach to disease control.