Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/12/2001
Publication Date: 4/1/2002
Citation: Wu, L., Liu, G., Yates, M.V., Green, R.L., Pacheco, P., Gan, J., Yates, S.R. 2002. Environmental fate of metalaxyl and chlorothalonil applied to a bentgrass putting green under southern California climatic conditions. Pest Management Science. 58(4):335-342. Interpretive Summary: Golf course putting greens receive frequent pesticide applications to maintain a high-quality grass surface. Pesticide use has the potential to adversely impact environmental and human health. This research on pesticide fate in turf systems is important to better understand the movement and dissipation of two commonly used fungicides, metalaxyl and chlorothalonil, in a bentgrass. The test plot (i.e., putting green) was maintained under customary field management practices at the University of California-Riverside Turf Research Facility during 1996 and 1997. Two fungicides were chosen due to differences in their chemical properties that affect movement and dissipation. The results showed that cumulative emissions were less than 0.1 percent, losses due to clipping removal were less than 0.13 percent, and leaching losses were less than 0.71 percent. Both fungicides were found predominately in the upper 10 cm of soil, due to high soil organic carbon contents. The dissipation half life was 1.4 d and 4.9 d, respectively, for metalaxyl and chlorothalonil. This study demonstrated that offsite transport was minimal under normal turf management practices.
Technical Abstract: Putting greens usually receive high inputs of fertilizers and pesticides to meet the high demand for visual quality and to overcome the stress from close mowing and traffic. In this study, two commonly used fungicides, metalaxyl (methyl N-(methoxyacetyl)-N-(2,6-xylyl)DL-alaninate) and chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile), were evaluated for their partitioning and persistence in a bentgrass (Agrostis palustris Huds) putting green under Southern California climatic conditions. The putting green site was constructed according to the US Golf Association (USGA) specifications. Lysimeter assemblies installed at the center of each plot were used to monitor the leachate, flux chambers were used to measure volatilization, clippings were collected to determine the residues on grass, and soil cores were sampled to determine residues in the soil profile. Results showed that cumulative volatilization loss accounted for 0.10 and 0.02 percent, clipping removal 0.11 and 0.13 percent, and cumulative leaching 0.71 and 0.002 percent of the applied metalaxyl and chlorothalonil, respectively. The two fungicides were mainly found in the top 10 cm of the soil profile due to the high organic carbon content in the thatch and mat layers. The dissipation half-life was 1.4 days for metalaxyl and 4.9 days for chlorothalonil on grass, short than those found in agricultural fields. This study showed that, under normal turf management practices, the offsite transport of the parent fungicides was minimal. Future research should focus on investigating the fate and mobility of the metabolites of the fungicides.