P-099 - The effect of flight parameters on unmanned aerial vehicle fungicide spray coverage, deposition, and disease control.

A trial was established in Princeton, KY in 2024 to examine the effects of flight speed and height above crop canopy on spray coverage, spray deposition, and disease control in corn. A fungicide mixture of prothioconazole + trifloxystrobin + fluopyram (0.58 L/ha), non-ionic surfactant (0.25% v/v), 1,3,8-pyrenetetrasulfonic acid (PTSA; 600 ppm), and acid blue 009 (1% v/v) was applied to corn at tasseling/silking (VT/R1) using a DJI T10 sprayer. Fungicide treatment was applied at a flight speed of 4.3 or 5.8 m/s at 2.3 or 3 m height above canopy. Spray coverage was determined as the percentage of spray card (7.62 x 43.18 cm) area covered by blue dye, analyzed with a Swath Gobbler (Application Insight, LLC). Spray deposition data was collected and converted to the concentration (µL/cm²) of spray solution recovered from 12 leaves per plot. Disease severity was rated as the percentage of ear leaf covered by foliar diseases at dough (R4). All data were analyzed in SAS 9.4 using PROC GLIMMIX.  Flight speed had a significant effect on fungicide coverage (P = 0.0127), with plots sprayed at 4.3 m/s from a height of 2.3 m exhibiting significantly higher (P = < 0.001) coverage compared to all other treatments. There was no significant effect of flight speed or height on spray deposition. Gray leaf spot was significantly higher (P = 0.0195) in plots sprayed at 5.8 m/s from a height of 3 meters, but there were no significant differences in disease severity among the other foliar diseases rated.