Operationalizing insect resistance management for commercialized Bt crops: an evidence-to-action framework for post-market stewardship.

Commercialized Bacillus thuringiensis (Bt) crops require post-market stewardship that translates heterogeneous resistance signals into defensible action. Although previous syntheses have defined field-evolved and practical resistance and summarized global patterns, developers, regulators, and stewardship programs still need an operational structure for distinguishing weak anomalies from evidence warranting confirmation, mitigation, deployment revision, or replacement of compromised components. We synthesize evidence and stewardship experience from Bt maize and Bt cotton into an evidence-to-action framework linking preventive IRM implementation, resistance monitoring, evidence-state assignment, actionability assessment, and proportionate response. The framework classifies outcomes into four states: baseline susceptibility, early-warning signal, confirmed field-evolved resistance, and practical resistance. For each state, we define its operational meaning, minimum verification requirements, and proportionate actions. Representative pest - crop - toxin systems illustrate how field performance, bioassays, mechanistic evidence, deployment history, and refuge context can support earlier, more transparent, and evidence-proportionate stewardship decisions.