Temperature Influences Persistence of Chlorothalonil and Iprodione on Creeping Bentgrass Foliage

Fungicides play a critical role in the management of plant diseases, yet the impact of temperature on foliar fungicide persistence remains unclear. The objective of this study was to determine the relative persistence of chlorothalonil and iprodione on creeping bentgrass (Agrostis stolonifera L.) leaf blades at 10, 20, and 30°C during two separate experiments in 2011. A commercially available enzyme-linked immunosorbent assay (ELISA) was used to assess the relative concentration of both fungicides remaining both on and within the leaf tissue. Dissipation of both fungicides was greatest at 30°C and slowest at 10°C, while dissipation at 20°C was intermediate between 10 and 30°C and often not statistically different from either of the temperatures. Iprodione half-life over both trials averaged 51.2 days at 10°C, 7.8 days at 20°C, and 4.0 days at 30°C. Chlorothalonil half-life averaged 9.5 days, 4.3 days, and 4.0 days at 10, 20, and 30°C, respectively. These results indicate that fungicide persistence decreases with increasing temperature, which may help explain why fungicides more commonly fail to provide adequate disease protection during periods of hot temperatures. Accepted for publication 27 June 2015. Published 1 July 2015.