The Treatment Window Approach for Managing Diamondback Moth (Lepidoptera: Plutellidae) in Brassica Crops in Florida

摘要

The diamondback moth (DBM), Plutella xylostella (L.), is one of the most damaging pests of Brassica crops worldwide and is notorious for developing insecticide resistance. DBM has been a pest in Florida since 1883 and is now found in all cabbage producing areas of North America. In Spring 2016, growers reported uncontrollable DBM populations across the state. This widespread failure of chemical control suggests resistance development. It is customary in resistance management to avoid applying the same mode of action to successive generations of the same pest. The "treatment window" approach uses the average life cycle of pests to determine the time span in which modes of action should be alternated. A four-week treatment window may be used to designinsecticide rotations for DBM management. A fundamental question in chemical control of DBM is optimal placement of diamide and biorational insecticides in the rotation because these materials interfere least with the activity of parasitic wasps that attack DBM larvae and pupae. Three eight-week rotations were compared to an untreated control for management of DBM and other larvae attacking cabbage and collards. The trial compares application of the systemic diamide Coragen with Bacillus thuringiensisand the insect growth regulators Rimon and Dimilin. Insecticide rotations were evaluated based on suppression of the DBM and other Lepidoptera, enhancement of parasitism, and yield. Results will contribute to improved management of DBM and other caterpillars attacking Brassica crops in Florida.