Non-target effects of fungicides on creeping bentgrass (Agrostis palustris Huds.)

Zachary James Reicher, Purdue University

Abstract

Though many fungicide applications are made on a golf course in a year, little consideration is given to possible non-target effects of fungicides on turfgrasses. Since non-target effects are usually subtle and inconsistent, these effects must be better understood to use fungicides safely and effectively. The objective of this research was to determine the effect of four fungicides on creeping bentgrass (Agrostis palustris Huds.) growth and performance. Our hypothesis was that fungicides applied repeatedly and/or at high rates would negatively affect creeping bentgrass growth and/or water soluble carbohydrate (WSC) status. Fungicides used were benomyl (methyl-1-(butylcarbamoyl)-2-benzimidazolecarbamate), chlorothalonil (tetrachloroisophthalonitrile), iprodione(3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidinecarboximide), and propiconazole (1-(2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl)-1H-1,2,4-triazole). Single applications of fungicides at recommended rates had no negative side effects at any time during the studies. All applications of propiconazole consistently caused creeping bentgrass to turn dark green in all studies. Benomyl applied once at 1X, 3X, and 9X the recommended rate increased shoot growth in the greenhouse. Chlorothalonil, iprodione, and propiconazole reduced plant weights and iprodione and propiconazole 3X reduced WSC in the greenhouse. Repeated applications of propiconazole increased root-to-shoot ratios in the growth chamber. Nine applications of benomyl, chlorothalonil, and propiconazole over a four week period decreased growth whereas, nine applications of benomyl, iprodione, and propiconazole decreased WSC concentrations in the growth chamber. In a field study, 16 applications of fungicides in each of three years had few significant effects on a creeping bentgrass putting green. Fungicide treatments slightly improved rooting in the last year of the study. Propiconazole consistently decreased visual quality but improved color and increased shoot growth. Propiconazole increased snow mold incidence one spring. Three years of chlorothalonil or benomyl applications reduced earthworm populations. If turf is managed properly and fungicides are applied judiciously and at recommended rates, there are few negative non-target effects of fungicides on creeping bentgrass growth and performance.

Degree

Ph.D.

Advisors

Throssell, Purdue University.

Subject Area

Agronomy

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