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Compatibilities of Conventional Turfgrass Pesticides with Biological Disease Control Strategies 1998

Project Leaders: Eric Nelson, Cheryl Craft


1. Determine the direct toxicity of selected herbicides, insecticides, and fungicides to various 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 various microbial inoculants and compost amendments for the suppression of Pythium damping-off and root rot caused by Pythium graminicola, brown patch caused by Rhizoctonia solani, and dollar spot caused by Sclerotinia homoeocarpa.

3. Evaluate the efficacy of selected compost amendments and microbial inoculants when oversprayed with selected chemical pesticides.


This project was designed to examine the impact of pesticide applications on the efficacy of commercial microbial inoculants used to suppress turfgrass diseases. Results from the study revealed a number of important findings. First, and somewhat surprising, was the fact that a number of pesticides commonly used in golf turf management had significant toxicity to nontarget pathogens. This is best exemplified by the activity of Daconil against P. graminicola, Trimec and Merit against S. homoeocarpa, and Subdue Maxx against R. solani. These findings complicate the interpretation of bioassay results and complicate interpretations of field results when such pesticides are used in combination with biological agents. Second, our results clearly showed that a number of pesticides used in combination with inoculants could dramatically effect their suppressive qualities toward various diseases. This is best illustrated by the impact of Bayleton and Proxol on the suppression of P. graminicola by E. cloacae. Finally, our results showed that some commercially available microbial inoculants were suppressive to Brown patch and Anthracnose diseases.