Coumarin and 6-Methylcoumarin as Alternatives to Pesticides against Mustard Aphid Lipaphis erysimi (Kalt.)

The mustard aphid, Lipaphis erysimi (Hemiptera: Aphididae), represents a primary constraint to mustard (Brassica juncea) production in tropical and subtropical regions, inflicting yield losses of 20-92% through direct sap feeding, honeydew-induced sooty mold and virus vectored diseases. Conventional synthetic insecticides such as neonicotinoids (Imidacloprid and thiamethoxam) deliver rapid control (80-95% mortality) but engender resistance, pollinator decline and environmental persistence, requiring sustainable alternatives within integrated pest management. This review evaluates coumarin (1-benzopyran-2-one) and its derivatives, notably 6-methylcoumarin, as promising botanical pesticides for L. erysimi management. Coumarins, secondary metabolites from diverse plant families (Apiaceae, Fabaceae), exhibit potent aphicidal activity, with LC50 values of 14.2 μg/mL against cotton aphid Aphis gossypii comparable to malathion while demonstrating >10-fold selectivity over honeybees via differential acetylcholinesterase (AChE) inhibition. Molecular docking reveals 6-methylcoumarin binding to aphid AChE peripheral anionic site (Lys585), inducing neurotransmitter accumulation, paralysis secondary reactive oxygen species (ROS) overproduction, alongside GST/esterase suppression. Field simulations project 70-85% population suppression (7 days after treatment) from 0.2-0.5% foliar sprays, yielding 25-35% higher pod weights versus untreated controls, with rapid degradation (DT50 = 1-3 days) ensuring low residues ( 120 μg/bee) affirm environmental compatibility. Challenges include limited L. erysimi-specific field data and potential hepatotoxicity at high doses, addressable through QSAR-optimized analogs and Punjab-focused trials. Coumarin-based formulations present a biodegradable, cost-effective shift from synthetic dependance, boosting resilient Brassica agroecosystems amid global insecticide restrictions