Most herbicides are sprayed onto fields during application. As the droplets dry, non-volatile lipophilic herbicides spread into the epicuticular waxes present on the leaves and any fruit or vegetables present. Herbicides accumulate in these wax layers before migration to the active biological site, but the herbicides accumulated in or adsorbed on the epicuticular wax are subjected to solar light and may undergo photochemical transformation while in/on this layer. In our study of the photolysis of dicamba on corn and soybean plants, we removed the epicuticular wax from plant leaves to study the waxes separately. Plants were grown in the Gustavus Adolphus College greenhouse. Adjuvants in commercial herbicide mixtures, namely surfactants such as ethoxylated isodecyl ether, cause dicamba to spread more fully across the surface of epicuticular waxes and may increase the rate of reaction. To establish the role adjuvants play in the photochemical degradation of dicamba on epicuticular waxes, side-by-side experiments with dicamba-only solutions and dicamba solutions with adjuvants were conducted. HPLC and LC-MS were used to record photolysis rate constants and identify photoproducts. For comparison and as controls, experiments were also conducted on glass petri dishes and in aqueous solution. Pesticide reactivity is rarely examined on plant surfaces. This study examines the importance of photochemical reactions on crops after pesticide application, and could impact how researchers and regulators adjust lab conditions to better replicate field conditions.<br/>

Photochemical degradation of the herbicide dicamba on heterogeneous surfaces

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.