Efficacy of elicitors and conventional insecticides against insect pests on common bean (Phaseolus vulgaris L.) crop

The common bean (Phaseolus vulgaris L.) is a vital crop for food security and export in Egypt, yet its productivity is heavily constrained by infestations of aphids (Aphis craccivora) and leaf miners (Liriomyza trifolii). This study investigated the comparative efficacy of three plant defense elicitors—salicylic acid (SA), chitosan (CH), and pyroligneous acid (PA)—and three conventional insecticides—chlorpyrifos, imidacloprid, and emamectin benzoate—applied individually and in combination under laboratory and field conditions during the 2022 and 2023 growing seasons.Laboratory assays using the leaf-dip method were performed to determine LC₅₀ and LC₉₀ values, while field experiments were arranged in a randomized complete block design (RCBD) with 11 treatments and one untreated control, replicated three times. Treatments were evaluated for their impact on pest suppression, sublethal effects (aphid fecundity and leaf miner tunnel length), and crop performance (biological, seed, and straw yields).Results demonstrated that combinations, especially chlorpyrifos + SA, imidacloprid + SA, and emamectin + SA, achieved the lowest LC₅₀ values and produced the highest pest suppression. Under field conditions, pest reduction reached 77.2%, with emamectin + SA and chlorpyrifos + SA being most effective. These treatments significantly reduced aphid reproduction and tunneling activity of leaf miners. Yield improvements were also observed, with seed yields reaching 6.15 kg per 21 m² plot (≈1230 kg/feddan).In conclusion, integrating systemic insecticides with biochemical elicitors enhanced pest control efficacy, minimized chemical reliance, and improved crop productivity. This approach offers a sustainable and resilient integrated pest management (IPM) framework suitable for Egyptian legume cultivation systems.