Efeitos letais e subletais do isocicloseram sobre Myzus persicae e seu predador natural Allograpta exotica

Abstract

Insect pests, including the green peach aphid Myzus persicae, cause significant damage to various crops, and the use of insecticides is a common method for their control. Hoverfly larvae are natural predators of aphids and other plant-sucking insects and play a critical role in regulating pest populations in agricultural systems. However, the use of insecticides can have lethal and sublethal effects on these beneficial insects, potentially affecting their biological traits and their effectiveness in aphid control. This study aimed to evaluate the lethal and sublethal effects of isocycloseram on the longevity and reproductive traits of M. persicae and its natural predator Allograpta exotica, focusing on the following biological traits such as longevity, fecundity, pupal weight, developmental time, and predation rate. The study was carried out at the Molecular Entomology and Ecotoxicology Laboratory (MEET) at the Federal University of Lavras. The rearing of M. persicae was maintained under controlled conditions at 20 ± 2 °C, 70 ± 10% relative humidity, and a 16-hour photoperiod, whereas A. exotica was kept in a climatic chamber at 25 ± 2 °C, 50 ± 7% relative humidity, and photoperiod of 12:12 h. Toxicological bioassays consisted of exposing adult M. persicae and A. exotica larvae to seven concentrations to determine the LC 50 and LC 90 values. Mortality caused by isocycloseram was assessed after 48 hours, and the dose-response curve was determined. Subsequently, the sublethal effects on adult M. persicae and A. exotica larvae were evaluated. Fifty repetitions for 5 replicates of adults M. persicae and fifty repetitions for 3 replicates of second instar larvae of A. exotica were exposed to sublethal concentrations (LC 1 , LC 5 , LC 10 , LC 25 ) and to the control. The longevity and fecundity of M. persicae were recorded daily until death. The evaluation of A. exotica larvae began at the second instar and continued until the death of the newly emerged adults. Each larva was offered 20 adult aphids per day, to assess its development time and predatory capacity, and the biological traits of adults emerging from sublethal exposed larvae. The results showed significant differences among all evaluated parameters. However, according to our findings, the use of isocycloseram in Integrated Pest Management (IPM) programs requires further research to ensure the safety of natural enemies.