A Systematic Review of Ethnobotanical and Traditional Knowledge on Plant Extracts Reported to Repel Wild Boars

Abstract

The Indian Wild Boar (Sus scrofa cristatus) has become one of the most economically damaging vertebrate agricultural pests in South Asia. Farmer surveys in Himachal Pradesh report yield losses of 60-80% in badly affected fields, while national estimates place average multi-crop damage at 15-20% across maize, jowar, rice, Brassica spp. and vegetables, with the species consistently ranked among the top crop-raiding animals in household-perception studies. Because wild boar retain an IUCN “Least Concern” status and are currently listed under Schedule II of the Wildlife (Protection) Act, 1972 (as restructured by the 2022 amendment; formerly Schedule III under the original six-schedule framework), lethal control remains legally constrained, which positions non-lethal, farmer-adoptable repellents as the primary management pathway for smallholders who cannot afford solar or electric fencing (₹10,000-₹3,00,000 per acre). Wild boar relies predominantly on an exceptionally developed olfactory system (over 1,300 olfactory receptor genes, active from the prenatal stage) and possess comparatively weak, dichromatic vision, a combination that supplies a physiological rationale for odour- and taste-based botanical deterrents such as capsaicinoids and organosulfur compounds. However, the field evidence for such repellents is markedly inconsistent. This review synthesises the background of the conflict – including India’s 2025 policy shift adding wild-animal crop loss as a Pradhan Mantri Fasal Bima Yojana (PMFBY) add-on cover, and Kerala’s unresolved vermin-declaration dispute – alongside the sensory and behavioural biology that governs repellent design, and the primary field literature on ethnobotanical and botanical repellent efficacy. The review concludes that ethnobotanical repellents hold genuine but presently unproven promise for Indian smallholder agriculture, contingent on the development of controlled-release delivery systems, standardised efficacy protocols, and their integration within a broader Integrated Pest Management (IPM) framework rather than deployment as a stand-alone solution.