Phototransformation of Bifenthrin and Methoxyfenozide Residues on Pistachio (Pistacia vera) Hulls and Model Surfaces
AuthorBenedetti, Philip R.
Civil and Environmental Engineering
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Phototransformation of two pesticides, bifenthrin and methoxyfenozide, were studied on the surfaces of pistachio nut hulls and other model surfaces after application using a laboratory spray chamber. The experiments were carried out using pistachio nut hulls, glass microscope slides, glass pistachios, glass microfiber filters, and cellulose filter papers. The pure compounds were investigated under simulated sunlight using a xenon arc lamp (λ > 300 nm). At the recommended agricultural application rates, both pesticides transformed more rapidly on all of the surfaces tested than previous studies using natural sunlight have shown on soil or in solution. The primary factors influencing transformation rates were shown to be macroscale surface geometry. Expected field half-lives obtained on pistachio surfaces for bifenthrin and methoxyfenozide were 18 and 30 days, respectively, and were shown to be in agreement with previous studies demonstrating residual activity for navel orangeworm control. This work highlights the importance of evaluating the photoreactivity of pesticides under conditions that are most similar to the environment of their application.