Pesticide decay in turf: a review of processes and experimental data

Decay rates are central parameters in modeling pesticide fate and transport in the environment. Pesticide decay is usually modeled as a first-order process, and variations in half-life can have significant impacts on model predictions. Decay rates for the foliage and thatch components of turf are scarce, and most simulation efforts must resort to values based on pesticide behavior in soil. This paper describes the main dissipation processes affecting pesticides applied to turf and compares aerobic soil decay rates from the USDA-Agricultural Research Service Pesticide Properties Database (ARS PPD; USDA-ARS, 2006) and from The Pesticide Manual (Tomlin, 2003) to dissipation values in turf found in the literature for 18 pesticides currently registered for turf. Median half-lives were 39.5 d for the ARS values, 35.8 d for Tomlin's values, and 5.7 d for the turf-specific values. The turf dissipation half-lives are considered to be representative of the microbial decay processes occurring in the foliage and thatch layers of well established turf, where the majority of the pesticide is intercepted and retained.