Taxas de aplicação e adjuvantes no controle da lagarta do cartucho no milho empregando drone de pulverização

Abstract

Drones have proven to be essential tools, widely used for spraying annual and perennial crops across various contexts in Brazilian agriculture. Operational efficiency is a key factor in agricultural operations, guiding decision-making and often impacting the quality of chemical applications and pesticide performance. This study aimed to investigate how reducing the application rate (120, 30, and 10 L ha⁻¹) influences the control of the fall armyworm (Spodoptera frugiperda) and how the use of different adjuvants (Aureo®, Ochima®, and Silwet L77®) affects the performance of applications using remotely piloted aircraft (RPAs). To this end, two field experiments were conducted during the 2024 off-season to analyze the interaction between these factors and their influence on the efficacy of the systemic insecticide tetraniliprole (Vayego®) for fall armyworm control and on crop yield. Additionally, laboratory analyses were performed to measure the surface tension and contact angle of droplets formed from the spray solutions. Samples were also collected from the whorls of treated plants to quantify the amount of active ingredient present in the target area. Fall armyworm control using drones showed significant differences beginning three days after the first application in terms of the percentage of infested plants, which ultimately impacted yield. After the second application, no significant differences in efficacy were observed among the treatments. Laboratory analyses revealed significant interaction between the evaluated factors, confirming the presence of surfactants in the commercial product formulation. No significant differences were observed between the adjuvants Aureo® and Ochima®, either when compared to each other or to the commercial product, provided that the critical micellar concentration (CMC) was reached. However, the surfactant properties were reduced as the spray volume increased. Silwet L77® exhibited greater surface activity, resulting in a lower droplet contact angle on the standard surface. Oil-based adjuvants showed intermediate surface tension and contact angle values, with combinations that led to higher absorption of the active ingredient. An application rate of 10 L ha⁻¹ resulted in higher concentrations of insecticide in the plant whorl, except for the treatment with Silwet L77®. No performance improvement was observed when increasing the application rate from 30 to 120 L ha⁻¹. These findings suggest that RPAs have strong potential as an effective method for insecticide application to control S. frugiperda and potentially other maize pests. Furthermore, the choice of adjuvant directly influences molecule absorption and control efficacy, highlighting the need for precise adjustments in drone-based applications.