Insecticidal activity of Cashew Nut Shell Liquid (CNSL) against pulse beetle (Callosobruchus maculatus) in green gram (Vigna radiata) seeds

Stored pulses are highly vulnerable to infestation by pulse beetles, particularly Callosobruchus maculatus, leading to significant postharvest losses. The insecticidal potential of Cashew Nut Shell Liquid (CNSL) against C. maculatus was evaluated using time-based toxicity assessments. CNSL was extracted using acetone and chemically profiled through Gas Chromatography-Mass Spectrometry (GC-MS). Major constituents included cardanol, gallic acid, oleic acid and 2-deoxy-D-glucose, compounds known for their neurotoxic, oxidative and metabolic-disrupting properties. Adult beetles were exposed to CNSL treated green gram seeds and mortality was recorded at 24, 48, 72, 96 and 120 hr post-treatment. Results revealed a strong time-dependent toxicity of CNSL, with LC₅₀ decreasing from 12.56 g/kg at 24 hr to just 0.62 g/kg at 120 hr. The regression models showed high reliability (X² = 0.966 - 1.000), confirming the dose-response relationship. Thus, the study demonstrates that CNSL is an effective botanical insecticide with increasing efficacy over time. Its multi-target mode of action and low-dose effectiveness highlight its potential as a sustainable solution for managing pulse beetles in pulse storage system.