Foliar Fungicides Reduce Short Term Non‐Target Soil Microbial Activity and Community Structure

Abstract

Pesticides are essential in modern agricultural practices and are used frequently for the protection of crops. Fungicides are a group of pesticides that inhibit the establishment of fungal pathogens. Our systematic knowledge of the different affects fungicides have on non‐target organisms, unfortunately, is inadequate. It is difficult to determine the range of organisms affected by fungicides because of the variability and sensitivity of both eukaryotes and prokaryotes. A laboratory study was initiated to assess non‐target effects of fungicides on soil microbes. This study examined the effect of the common fungicides Tilt and Trivapro at different concentrations and incubation periods for their non‐target effects on soil microbial communities and selected activities. Three rates, 0X, 1X (0.0058 μL/cm2) and 2X (0.0116 μL/cm2) of each fungicide were applied to 100 g of Bastrop soil, common to the Blackland Prairie of Central Texas. Significantly lower CO2 was respired from amended soils compared to the control. Additionally, nitrate mineralization concentration decreased over the 30‐day trial period compared to the control. Low carbon mineralization and nitrogen mineralization rates are both attributed to a decrease in soil microbial activity. Plate counts indicate fungi (PDA) and bacteria (TSA) showed variability at two sampling dates indicating that treatment effects could not be determined solely on population counts. Our results suggest these fungicides at 1X and 2X rates have significant effects on non‐target organismal activity and community structure. Future studies will examine field applications and reassess results.Support or Funding InformationUSDA Agricultural Research Service CRIS #3098‐13610‐008‐00D