Utilizing Action Thresholds in Small-Plot Insecticide Evaluations Against Cabbage-Feeding, Lepidopterous Larvae1

Insecticide efficacy against diamondback moth, Plutella xylostella (L.), imported cabbageworm, Pieris rapae (L.), and cabbage looper, Trichoplusia ni (Hübner), on cabbage was investigated, using a threshold of 0.5 total larva per plant as a basis for comparison. Materials were evaluated on the basis of control achieved, frequency of application necessary for control, and crop marketability. Results indicate that evaluating materials on this basis is useful in determining how they may best be incorporated in a scouting decision-making system.