Cabbage White Butterfly
Is white with distinct black spots on the wings and is around 40mm across. They lay their eggs on the underside of leaves. The caterpillars hatch from the eggs, then feed on the leaves or fruit. So it’s the caterpillar of the cabbage white butterfly which does the damage. They start eating the outer leaves before moving to the inner heart of the cabbage. It’s a good idea to try and either pick off the caterpillars or spray them when they are still on the outside of the leaf, before they tunnel into the heart.
Symptoms include large holes in outer leaves, and bluey-green bits on the inside of the leaf, or in the heart of the cabbage. This is called “Frass” and is actually the caterpillar poop!
If you spot Cabbage White Butterflies around your garden, protect your plants with insect mesh (like an old net curtain) to prevent the butterflies from laying eggs on your plants.