Nontarget Activity of Chlorpyrifos and Hydrolysis Products on Sclerotium rolfsii. A. S. Csinos, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793. Plant Dis. 69:254-256. Accepted for publication 23 September 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-254.

The insecticide chlorpyrifos (technical), two formulations (15G and 4EC); two hydrolysis products (3,5,6-trichloro-2-pyridinol and 2-methoxy 3,5,6-trichloropyridine); the stabilizer (γ-butyrolactone); and the clay carrier were evaluated and compared with PCNB 10G for their activities in reducing radial growth, sclerotial initials formation, and germination of mature sclerotia of Sclerotium rolfsii. The hydrolysis product 3,5,6-trichloro-2-pyridinol, the most active chlorpyrifos-related material tested, reduced radial growth at concentrations of ≥1 μg/ml, sclerotium formation at 1–25 μg/ml, and sclerotial initials formation and sclerotial germination at 1–10 μg/ml. At a concentration of 25 μg/ml, 3,5,6-trichloro-2-pyridinol equaled PCNB in its antifungal activity. The chlorpyrifos technical and 15G and 4EC formulations were less active than 3,5,6-trichloro-2-pyridinol (listed in increasing order of activity). The other materials were not active. Implications of antifungal activity of an insecticide and dynamics of hydrolysis in soil are discussed.