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Impacts of Conventional Turfgrass Pesticides on the Efficacy of Composted Amendments Used for the Biological Control of Turfgrass Diseases 1997

Project Leaders: Eric B. Nelson , Cheryl M. Craft

Objectives:

1. Determine the in vitro toxicities of herbicides, insecticides, and fungicides to selected turfgrass pathogens so that laboratory and field results may be properly interpreted.

2. Examine, in laboratory studies, the impacts of high label rates of various chemical pesticides on the efficacy of compost-amended topdressings for the suppression of Pythium damping-off and root rot caused by Pythium graminicola and other appropriate diseases.

3. Evaluate, under field conditions, the efficacy of selected compost amendments when combined with chemical pesticides.

Results:

Although none of the pesticides tested reduced or enhanced the suppression of Dollar Spot or Brown Patch by compost amendments, the pesticides themselves had dramatic effects on disease development. Each of the insecticides and herbicides tested significantly enhanced Brown Patch disease. The fungicide Heritage effectively controlled the disease. Effects on Dollar Spot disease were the opposite: the herbicide Pre-M and the insecticide Dursban significantly suppressed the disease, whereas Heritage significantly enhanced diseases severity. (The other pesticides tested had no effect on Dollar Spot severity.)