Dislodgeable Foliar Residue (DFR) is a frequently used environmental measurement for estimating reentry worker exposures in agricultural settings. It is defined as the pesticide residue that can be removed from both sides of the treated leaf surfaces using an aqueous surfactant. This portion of the leaf residue is assumed to be available for transfer to agricultural workers contacting the foliage. But measured DFR is not always available for certain active ingredients (AI). When data are entirely lacking, regulators may use a default of 25% of the application rate as a surrogate for the pesticide residue available on the day of the application (initial DFR). Additionally, when DFR dissipation data are not available, regulators may assume a default dissipation of 10% per day. Different leaf textures such as hairy, smooth, and waxy may impact the deposition of AI on foliage, the extent to which it is dislodgeable, and also affect the DFR dissipation. Using data collected in California, we compared the initial measured DFRs with the default 25% DFRs for various crops grouped in each of the leaf texture categories. We also compared dissipation from linear regressions of log-transformed DFR measured on multiple days with the 10% daily dissipation default. These comparisons indicated that the initial DFRs may be affected by leaf texture for many AIs, but did not appear to support a dependence of dissipation rates on leaf texture.

Impact of leaf texture on dislodgeable foliar residue on various crops in California

248th National Meeting (2014)

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