Final Report: April 30, 2021

Principal Investigator: Peter Ako Larbi, University of California Agriculture and Natural Resources, 9240 S Riverbend Ave, Parlier, CA 93648, (559)-646-6577, [email protected]

Cooperator(s): George Zhuang, C.E. Viticulture Farm Advisor, UCCE Fresno County, 550 E. Shaw Ave, Suite 210-B, Fresno, CA 93710, (559)-241-7506, [email protected] Objective(s) and Experiments Conducted to Meet Stated

Objective(s): The project goals and objective are summarized in Figure 1 below. The objective of this study was to generate data from grape airblast applications for validation of a mechanistic model being developed to assess risk from airblast spraying by estimating exposure values. Measurements were made to facilitate the assessment of drift related to key application and meteorological systems.

Our single objective in this project was to conduct airblast spray trials in the field to generate spray drift data that will be used to validate a computer model. The model is intended to be used by regulators for evaluating spray drift risk of airblast spray applications by estimating pesticide exposure values. This work is of significant relevance in the sense that the ability of regulators to evaluate drift exposure values more realistically will minimize the severity of regulations affecting growers. In the project period covering May1, 2020to April30, 2021, we pursued and obtained all funding required to replicate the study in three crops (almond, citrus, and grape) sharing resources. We built sampling structures needed for the field experiment, purchased shared resources, and configured/tested meteorological instruments for the field data collection. We set up the experiment in a commercial ‘Vintage Red’ table grape vineyard in Del Rey, CA from the second half of October 2020through the first week of November. We carried out the field experiment following an EPA-approved protocol to be used in all three crops. Samples collected were analyzed at the UC ANR Agricultural Application Engineering Laboratory to obtain the drift data along with processed weather data. The complete data generated will be made available, along with associated reports, in corporation into the orchard and vineyard airblast spray drift model.

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