Management of Insect Pests on Cole Crops with Low-Risk Pesticides
Cole crops such as head cabbage, Chinese (Napa) cabbage, and mustard cabbage are grown throughout the year in Hawaii. These crops are grown sequentially in adjacent fields on farms that are clustered on three major islands, Hawaii, Maui and Oahu. Insect pests and diseases occur throughout the year and pesticides are required to meet market grade standards. The biopesticides, Spinosad and Bacillus thuringiensis, are commonly used for control of caterpillars but growers continue to rely heavily on organophosphates, carbamates and pyrethroid insecticides. The project demonstrates to growers that registered and soon to be registered low risk pesticides can be used in conjunction with naturally occurring biological control organisms to manage common pests on cole crops. The project also demonstrated an effective pesticide resistance management program by rotating low risk pesticides.
Project goals and objectives
1) Demonstrate to growers that registered and soon to be registered low risk pesticides can be used in conjunction with naturally occurring biological control organisms to manage common pests on cole crops.
2) Demonstrate an effective pesticide resistance management program by rotating low risk pesticides.
The predominate caterpillar species infesting the cole crop in all three field tests was the diamondback moth, Plutella xylostella. A rotation of two insecticides - spinosad (Success, Dow AgroSciences) and emamectin benzoate (Proclaim, Novartis) was planned as the Low Risk Pesticide treatment for caterpillars. However, approval for the latter insecticide by EPA was delayed so only spinosad was used as the LRP treatment. Consequently, pesticide resistance management was eliminated as an objective. The standard practice of all cooperating growers was a rotation program of Bacillus thuringiensis and spinosad. However, the field demonstrations showed growers they could improve on their standard practices. The trials showed that a combination of a Low Risk Pesticide and regular pest monitoring using action thresholds (0.5 larva/plant) could result in equal or greater marketable yields at lower cost. For example, in one of the general practices fields, a total of seven pesticide applications were made but only four applications were made in the comparable low risk pesticide field.