Impact and selectivity of insecticides on groundnut predators

Abstract

Predatory arthropods play a crucial role in mitigating the impact of insect pests. However, the use of broad-spectrum insecticides in pest management methods can pose a threat to predator populations. In response to the need for safer and more selective insecticides that spare natural enemies, an effort was made to know the diversity of predatory fauna and effect of seed dressers and foliar spraying insecticides on coccinellids and spiders at the Main Agricultural Research Station in Dharwad, Karnataka, during the summer 2021 and 2022. The treatments included four seed treatments, four seed treatments in combination with foliar spray, two foliar sprays alone, and an untreated control. Predator numbers were recorded at 45 and 65 days after sowing (DAS), selecting 20 plants randomly in all treatments. The results demonstrated that during the summer 2021 and 2022, seed treatment with chlorpyriphos 20EC was identified as safe, exhibiting the highest number of coccinellids (0.55 and 1.33 per plant) and spiders (0.54 and 1.62 per plant), respectively. These results were statistically comparable to other treatments like, seed treatment with imidacloprid 60 FS (0.49 and 1.00 coccinellids per plant) (0.48 and 1.38 spiders per plant), thiamethoxam 30 FS (0.45 and 0.95 coccinellids per plant) (0.44 and 1.22 spiders per plant) during 2021 and 2022 summer, respectively, ranking just below the untreated control. A significant difference in the population of coccinellids and spiders was observed among all the treatments, with seed-treated plants recording the highest predatory populations compared to foliar-sprayed plants. Consequently, the study concludes that seed treatment chemicals prove to be safer for predators while still effectively providing necessary pest control. This highlights the potential of integrating such seed treatment methods into pest management strategies to enhance overall efficacy while minimizing adverse effects on beneficial predator populations.

Keywords

• Coccinellids
• Foliar spray
• Seed treatment
• Spiders
• Summer