There have been sightings recently of imported cabbageworms on crucifer (cole) crops. This includes cabbage, broccoli, cauliflower, radish, kale, and turnips. Watch for holes in the leaves to indicate that they are feeding. Also watch for medium sized white butterflies in your garden. This in the adult stage of this pest. If they are present, watch your crucifers closely for evidence of the caterpillars.
|Imported cabbageworm. Photo: Jeffrey Hahn, UMN Extension|
Early detection is important; the sooner you can find imported cabbageworms, the sooner you can take steps to minimize their damage. Be sure to look on both sides of the leaves when inspecting plants. Handpicking can be effective management, especially if your garden is not too large. Bacillus thuringiensis and spinosad are low impact insecticides effective against these caterpillars. Effective, residual insecticides include permethrin and lambda cyhalothrin.
For more information, see Caterpillar pests of cole crops in home gardens.