D3033: Insecticide efficacy and residuality on alfalfa plants and fall armyworm larval stage

Fall armyworm (FAW), Spodoptera frugiperda, is one of the most important pests in agriculture due to its capacity to feed on a wide range of crops, including maize, rice, sorghum, cotton, and vegetables. Native to tropical regions of the Americas, FAW has expanded its range, threatening cropping systems worldwide. Its ability to migrate long distances or move through wind streams can result in sudden outbreaks, causing devastating crop damage. In 2021, an outbreak of FAW in alfalfa and forage crops highlighted the lack of information on effective control strategies for this pest in alfalfa systems. This study evaluated the residual efficacy of seven insecticides commonly used in alfalfa crops, representing different IRAC classes. Third-instar FAW larvae were exposed to treated alfalfa leaves collected at 0, 3, 7, 14 and 21 days after insecticide application. Mortality was assessed at 12 and 36 hours post-exposure, along with feeding cessation and growth inhibition. The results aim to identify the most effective insecticide molecules and optimal application schedules for controlling FAW in alfalfa. This study provides critical insights for growers, contributing to improved pest management strategies and reducing the environmental impact of insecticide use.