Resistance Management Calculator

This calculator scores how much resistance-development risk your season's pesticide rotation plan is carrying, built from five multiplied factors rather than a single number. Selection pressure is just your stated control efficacy as a fraction — a more effective product kills more susceptibles and leaves a larger share of any resistant survivors to breed, so higher efficacy actually raises resistance risk, not lowers it. Generation-time factor uses a 30-day baseline: pests with faster generation cycles than 30 days multiply that factor above 1, since more generations per season means resistance genes propagate faster under the same selection pressure. Refuge factor rewards leaving untreated area for susceptible insects to persist and interbreed with survivors — 20%+ refuge cuts risk to 0.6× baseline, while under 10% leaves the full 1.0× penalty in place.

The consecutive-application penalty is where the two-in-a-row rule lives: using the same mode-of-action (MOA) group more than twice consecutively adds a 30%-per-extra-application penalty on top of the baseline, reflecting guidance from the Insecticide Resistance Action Committee (IRAC) that back-to-back applications of one MOA group are the single fastest path to field-level resistance. A diversity bonus further rewards rotating through three or more MOA groups per season. All five factors multiply together into a 0-100 risk score, bucketed into four risk categories, and the "seasons to resistance concern" figure is a rough inverse-of-risk estimate — useful for comparing rotation plans against each other, not a predictive timeline for any specific pest population's actual biology.