Evolutionary Toxicology of Insecticide Resistance in Indian Cereal Ecosystems: A Critical Appraisal of Selection Regimes, Mechanistic Evidence and Management Inference

Abstract

Insecticide resistance in the pest complexes of rice, wheat, maize and stored cereals represents one of the most consequential evolutionary responses to human chemical intervention in South Asian agriculture, yet the evidence supporting resistance management decisions in India remains uneven in both quality and coverage. This review evaluates critically the state of knowledge on the evolutionary toxicology of insecticide resistance in Indian cereal ecosystems, treating resistance as the outcome of quantifiable evolutionary parameters rather than as a descriptive property of pest populations. Literature was identified through open scholarly indexes and metadata registries, supplemented by citation searching, and appraised for design adequacy, mechanistic depth, geographical relevance and evidential alignment with the claims made. Four analytical themes are developed. First, the selection landscape of Indian cereal systems is characterised by near-continuous host availability, short generation times, extensive dispersal and a narrowing set of effective modes of action, a combination that theory predicts should accelerate adaptation. Second, mechanistic understanding of field-evolved resistance in rice planthoppers, stem borers and stored-grain beetles derives predominantly from East Asian, Brazilian and Australian laboratories, so that mechanisms are frequently assumed rather than demonstrated for Indian populations. Third, phosphine resistance in stored cereals constitutes the clearest exception, since an India-specific dihydrolipoamide dehydrogenase variant has been characterised genetically and surveyed at high frequency in southern India. Fourth, the Indian field literature is dominated by short-term efficacy trials and single-season bioassays that cannot estimate allele frequencies, dominance, fitness costs or rates of change, which are precisely the parameters that resistance management strategies require. The principal unresolved questions concern the frequency and geographical structure of resistance alleles in Indian populations, the magnitude and modifiability of fitness costs, and whether recommended rotations achieve genuine heterogeneity of selection at the scale at which pests actually disperse. Resistance management in Indian cereals will remain provisional until longitudinal, genotype-based surveillance replaces episodic phenotypic screening.