Paper wasps for cabbage worms
In a 2024 Iowa State trial, native Polistes metricus colonies moved into a hoop house removed every imported cabbageworm, cabbage looper and diamondback moth caterpillar placed on broccoli, and leaf damage fell. Paper wasps hunt by sight and return to patches where they have found caterpillars before. The trial was short and screened, so treat nearby nests as a bonus alongside hand-picking and Bt, not a replacement.
Before you act
Slender wasps with a thin waist and dangling legs, nesting in open, umbrella-shaped paper combs under eaves. They hunt caterpillars to feed their larvae, and they can sting. A nest away from doors and paths is usually worth leaving. How to recognise it, what it is confused with and how to keep it around are on the full Paper wasps profile.
Other controls for cabbage worms
- Bacillus thuringiensis kurstakiMicrobial insecticide · Label rate — Thuricide 1–3 tsp per gallon for imported cabbageworm on broccoli, Brussels sprouts, cabbage, cauliflower, collards and kale; DiPel DF 0.5–2 lb per acre
- Braconid waspsWild parasitoid · Nothing to release — leave parasitised caterpillars and cocoon clusters on the plant
- Trichogramma spp.Egg parasitoid wasp · One card of about 100,000 T. brassicae per acre per week, for about 4 weeks or through the crop (UMass); 1–2 /ft² in gardens
- Tachinid fliesWild parasitoid · wild, attract it