Post‐application irrigation timing affects dislodgeable azoxystrobin foliar residue

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AbstractAzoxystrobin is a systemic broad‐spectrum fungicide used extensively in turfgrass. Previous research has shown post‐application irrigation can reduce dislodgeable pesticide residues from turf; however, this management practice has not been evaluated to determine its effect on dislodgeable azoxystrobin residue or if altering post‐application irrigation timing (PAIT) can influence dislodgeable azoxystrobin. Field research was completed to assess the effect of PAIT, sample collection timing within a day and over days on dislodgeable azoxystrobin residue from perennial ryegrass (Lolium perenne L.). Research was completed in Raleigh, NC, to quantify dislodgeable azoxystrobin (0.54 lb a.i. acre–1) from perennial ryegrass foliage prior to and following PAIT (0.25 inch H2O) immediate, 4, or 144 hours after treatment (HAT). Sample collections occurred 1, 2, 3, 6, 12 or 24 days after treatment (DAT) at 7:00 a.m. or 2:00 p.m. EST. From 1 to 6 DAT, treatments irrigated immediately reduced dislodgeable azoxystrobin foliar residue (<0.1–6.8% of applied) more than those irrigated 4 HAT (0.4–10.3%); which were both less than withholding irrigation 144 HAT (1.3–15.5%). Across PAIT more azoxystrobin was dislodged in the morning (1.0–12.7% of applied) compared to the afternoon (0.2–9.0%) from 1 through 6 DAT. This research will enhance turfgrass management practices intended to limit human pesticide exposure and provide information pertaining to azoxystrobin dissipation kinetics in turfgrass systems.