Dissipation of Foliar Bifenthrin Residues after Application to a Tall Fescue Lawn and Implications for Human Exposure

Abstract

Dislodgeable foliar residues (DFR) can be a primary route for human exposure after pesticide application to turfgrass areas. Consequently, a significant portion of applied pesticide may be available for human exposure via dislodgeable residues. In this study, DFR were determined over a 15‐d period after 6 Oct. 2006 application of the insecticide bifenthrin {2‐methylbiphenyl‐3‐ylmethyl (1RS,3RS)‐3‐[(Z)‐2‐chloro‐3,3,3‐trifluoroprop‐1‐enyl]‐2,2‐dimethylcyclopropanecarboxylate} to a mature stand of ‘Confederate’ tall fescue (Festuca arundinacea Schreb). Foliar residues were determined by wiping treated turfgrass with a distilled‐water‐dampened cheesecloth and analyzing samples using gas chromatography–mass spectrometry. Approximately 35% of the total applied bifenthrin (213,000 ng dm−2) was available to be dislodged over 15 d with 34% DFR loss occurring immediately after application. Residue loss measured 3 and 8 h after treatment contributed an additional 0.5% of the total applied bifenthrin dislodged from the foliar surface. Maximum bifenthrin DFR detected immediately after application resulted in a maximum estimated hazard quotient of 1.1 × 103 for the 15‐d study, indicating possible human toxicological implications. Residue levels detected 2, 5, 7, 11 and 15 d after application measured <1% of total applied bifenthrin, indicating minimal human health risk when applied at the labeled rate.