Lesson 4
Caterpillars
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The cabbage white butterfly's caterpillars can strip a kale plant in 48 hours. Tomato hornworm and cutworm cause similar drama. The good news: caterpillars are slow, visible, and easy to remove by hand.
Caterpillar control toolkit
- 1Fine insect mesh from sowing time over brassicas — physical exclusion is the best defence.
- 2Hand-pick adults at dusk; squash eggs weekly during summer.
- 3Bacillus thuringiensis (Bt) — a targeted bacterial spray that only affects caterpillars; safe for pollinators.
- 4Encourage birds — a bird bath and a single perch nearby brings sparrows and tits that eat caterpillars all day.
Identify before you treat
- Cabbage white — yellow eggs in clusters, pale green caterpillars on brassicas. Crush eggs weekly.
- Tomato hornworm — large green caterpillar with a 'horn'. Hand-pick; check daily.
- Cutworm — fat brown grub that severs young seedlings at soil level. Place a cardboard collar around stems.
- Codling moth — pinkish grub inside apples. Pheromone traps in spring.