STUDIES OF THE DISTRIBUTION, DRIFT, AND VOLATILIZATION OF DIAZINON RESULTING FROM SPRAY APPLICATION TO A DORMANT PEACH ORCHARD

An experiment was conducted to determine the spray distribution, spray drift, and volatilization of diazinon applied in the conventional manner with an air-blast sprayer to a dormant peach orchard. Copper hydroxide and a dormant oil were applied along with the diazinon. Soil samples and tree rinse samples were used to determine the distribution in the orchard. Airborne losses were calculated by the integrated horizontal flux method from measurements of wind speed and pesticide concentration profiles obtained during and for several days following application. Diazinon was not distributed evenly between the trees and the soil in the orchard according to their relative areas. Most of the diazinon accounted for was found to be on the soil. The residue on the soil dissipated with a 19 day half life. Application drift losses were small compared to long-term volatilization losses, and we conclude that most of the diazinon in California's Central Valley atmosphere during the dormant spray season results from volatilization. This result has important implications for designing strategies for controlling inadvertent contamination of other crops and the environment.