Bt on brassicas
Bt was placed on broccoli and cauliflower where caterpillars were feeding, including tight crowns and folds that were difficult to inspect by hand.
Bt targets feeding caterpillars and works only when they ingest treated material, so placement and reapplication after rain mattered.
Feeding pressure dropped after treatment, though a heavy later return showed that Bt is a monitored tool, not a one-time shield.