Volatilization of 14C-Labelled Fenpropimorph after Application to Plants and Soil under Simulated Outdoor Conditions

Abstract

The volatility of fenpropimorph was investigated in a laboratory chamber constructed for studying the volatilization of “4C-labelled pesticides from plant and soil surfaces. Summer barley was cultivated on experimental platforms (0.5 m²) filled with soil and treated in an application chamber with ¹⁴C-labelled fenpropimorph formulation (Corbel^R) at the beginning of ear emergence. After application, the platform was transferred into the volatilization chamber where a 96 h outdoor weather scenario was simulated. The results of three experiments demonstrated that up to 60% of the initial total radioactivity could be released from the plant-soil system within 96 h, most of it being the unchanged ¹⁴C-fenpropimorph which undergoes a fast oxidative (degradation by solar irridation in the atmoshpere. Furthermore, ¹⁴CO, was detected in quantities of 1.1 to 1.8%. After plant extraction, however, mainly polar metabolites, such as fenpropimorh acid, were found four days alter application by Radio-HPLC-analysis. In order to evaluate the volatilization behaviour of fenpropimorph sprayed to bare soils, three additional experiments were carried out showing a volatilization rate of 11.4% at most, much lower than those of plant surfaces.