Impact and selectivity of insecticides on groundnut predators

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.

Comparative Studies of Lepidopteran Pest Incidence on JL 24 and DH 256 Varieties of Groundnut

This experiment compares the incidence of lepidopteran pests under protected and unprotected groundnut cultivation at AICRP on Groundnut, MARS, Dharwad, Karnataka in the kharif season of 2021–2022. In order to protect the protected plot from pests, protection measures were implemented at 50 DAS using flubendiamide 20 WG @ 0.5g/l for leaf-eating caterpillars. Based on the crop's phenology, observations were made. Spodoptera litura, Thysanoplusia orichalcea, Helicoverpa armigera, and Maruca vitrata, were deemed to be the main pests, with the remaining pests being of less significance based on their population density and type of damage. When comparing unprotected JL-24 and DH-256 crop plots to protected plots, the majority of major and minor pests were infested during the vegetative to maturity stage, with maximum infestation occurring during the pod formation and pod filling stages of the crop. In comparison to unprotected plots, protected plots had the highest pod and haulm yields.

Integrated Approach for Screening Groundnut Genotypes and Unveiling Morphological and Biochemical Factors Associated with Resistance to Thrips, Scirtothrips dorsalis Hood

Thrips is an important sucking insect pest and are the major problem in the groundnut. The pressure from thrips is higher in the summer. One species of thrips i.e., Scirtothrips dorsalis Hood was reported in the present investigation. To minimize crop losses, it is important to efficiently manage thrips, Scirtothrips dorsalis Hood. Finding the source of resistance is one strategy to reduce yield losses. In the summers of 2020 and 2021, forty-four groundnut varieties were screened in the field to determine their resistance to thrips occurrence. Nineteen genotypes were chosen for additional research, including host preference and oviposition preference tests in greenhouse conditions and host plant resistance studies, based on preliminary screening studies conducted at the field level in 2020 and 2021. None of the genotypes were totally free from thrips damage. Nonetheless, three genotypes (Dh-256, RST-1-2020-12, and INS-1-2020-11) were classified as resistant. Ten genotypes were very vulnerable, 14 were susceptible, and 17 were somewhat resistant. The biochemical and morphological examination results showed that resistance against thrips was conferred by increased levels of phenols, tannins, trichome density, and leaf colour