Cabbage white caterpillar

What you see

Two species. The large white lays clusters of yellow eggs and its caterpillars are hairy, yellow-and-black blotched, feeding in gangs. The small white lays single eggs and its caterpillar is plain velvety green, superbly camouflaged along the midrib.

Damage

Ragged holes chewed between the veins, working outside-in. Piles of dark green pellets in the leaf axils. On cabbage, tunnelling into the heart. Clusters of yellow eggs on leaf undersides.

Lifecycle on this coast

Two or three generations from spring to autumn, sometimes into December on this coast. Overwinters as a chrysalis on walls, fences and sheds - not usually in the soil.

When to act

Check leaf undersides weekly from April. Squash egg clusters on sight - it takes seconds and prevents everything that follows. Act on caterpillars while they are under a centimetre.

Months: April, May, June, July, August, September, October, November

Plants it bothers

Cabbage, Broccoli, Cauliflower, Curly kale, Brussels sprouts, Portuguese kale, Savoy cabbage, Rocket, Romanesco, Cavolo nero

Natural enemies

Parasitic wasp (Cotesia), Blue tit, Ground beetle, Spider, Wasp

Remedies

Insect mesh and fleece barrier, Bacillus thuringiensis (Bt), Encourage predators

The thing people get wrong

If you find a caterpillar covered in small yellow-white cocoons, leave it exactly where it is. Those are Cotesia wasp cocoons - that caterpillar is already dead and about to release dozens of parasitic wasps that will hunt the rest of your bed for free. Killing it is the worst move available.