Pests
Using Bt for cabbage worms
Bt (Bacillus thuringiensis) is a naturally occurring soil bacterium. It only affects caterpillars — bees, ladybugs, people, and pets are unaffected. It's the most reliable fix for cabbage worms on broccoli, cabbage, and cauliflower.
Steps
- Look for a spray labeled 'Bt kurstaki' or 'Bt var. kurstaki' at a garden center.
- Mix per the label — usually 1–2 teaspoons per quart of water.
- Spray in the evening or on a cloudy day; sunlight breaks Bt down.
- Coat both sides of the leaves — caterpillars have to eat it for it to work.
- Reapply every 7–10 days, and always after rain, until you stop seeing damage.
Helpful tip
Bt takes 1–2 days to kill caterpillars — they stop feeding almost immediately, but you'll still see them on the plant for a bit.