Particle drift potential of mesotrione and rimsulfuron plus thifensulfuron-methyl tank mixture in a low-speed wind tunnel

Particle drift happens during herbicide application when droplets travel outside the intended site. Different nozzles produce various range of droplets, so they play a very important role in coverage and drift occasions. When nozzles produce small droplets, the potential for off-target movement is very high. Another important factor determining particle drift is the distance between crops. Wind velocity gives the energy to herbicide particles to move away from the target place. Therefore, a drift simulation of herbicide (mesotrione and rimsulfuron plus thifensulfuron-methyl mixture) was done in a wind tunnel, using different nozzles Extended Range (XR) and Turbo TeeJet Induction (TTI). The wind speed was set at 4.4 m/s, representing the least favourable conditions where applications are possible. In the wind tunnel, eight crops (cantaloupe, cotton, green bean, pumpkin, soybean, sunflower, wheat, and watermelon) were positioned at 4, 6, 9, and 12 m downwind distances from the nozzle, and drift was simulated. Following treatments, plants were returned to a greenhouse for 28 days, and biomass reduction was recorded. Artificial collectors (Mylar cards) and water sensitive cards were positioned alongside plants. According to obtained results, spraying with XR nozzle influences higher injuries than TTI nozzle. Tracer deposition was higher at all distances when XR nozzle was used. Accordingly, droplet numbers, covered area, Volume Median Diameter (VMD), and deposition were higher on water sensitive cards when spraying were done using XR nozzle. As a consequence, higher biomass reduction occurred using the XR nozzle. The most sensitive crops were cantaloupe, pumpkin and sunflower, while the most tolerant were soybean and wheat.