Cabbage White Butterfly
Pieris rapae
The cabbage white butterfly's green caterpillars chew ragged holes in brassica leaves and can skeletonise seedlings if left unchecked.
The cabbage white butterfly is a common visitor to home vegetable gardens right across Australia, wherever brassica crops such as cabbage, broccoli, cauliflower, kale, rocket and bok choy are grown. The adult butterfly does no direct damage; it's the caterpillar stage that causes the feeding injury gardeners notice.
The adult is a medium-sized white butterfly with a wingspan of around 4–5cm. Males have one or two black spots on each forewing, females usually have two, and all have a dark smudge along the wing tip. They fly slowly and low over garden beds during the day, especially in warmer months, pausing to lay single, pale yellow, bullet-shaped eggs on the undersides of brassica leaves. The caterpillar (larva) that hatches is velvety green with faint yellow stripes running along its back and sides, growing to about 3cm long. It's well camouflaged against foliage and tends to sit along leaf veins or tucked into the heart of the plant, making it easy to miss at a glance.
Populations build through spring, summer and autumn, with several overlapping generations possible in a season. In cooler regions numbers drop off over winter, while in warmer parts of the country activity can continue year-round at a lower level. Butterflies are most active on warm, sunny days, which is when egg-laying peaks.
Management relies on regular inspection so caterpillars are caught early, before they reach the larger, more destructive later instars. Handpicking is effective for small plantings. Excluding butterflies with fine mesh netting or exclusion covers over seedlings and young plants stops eggs being laid in the first place and is one of the most reliable non-chemical controls. Encouraging parasitic wasps and other beneficial insects by planting flowering companion species nearby can also help keep numbers down over time.
How to identify
- Ragged, irregular holes chewed in leaves, often starting on outer leaves and moving inward to the developing heart of the plant.
- Skeletonised leaves where only veins remain, on badly affected seedlings.
- Small greenish-black droppings (frass) scattered on leaves and in leaf axils, a good sign caterpillars are present even if the caterpillar itself isn't visible.
- Pale yellow, bullet-shaped eggs stuck singly to the underside of leaves.
- White butterflies fluttering low over the bed during the day, particularly around brassica plants.
Field check: turn leaves over and look closely along the veins and in the heart of the plant; the green caterpillars blend in well and are easiest to spot in early morning or late afternoon light. Gently parting outer leaves of cabbages and broccoli often reveals caterpillars sheltering out of direct sun.
Lookalikes: the caterpillars of the cabbage moth (a mottled brown, night-active species) cause similar chewing damage but are grey-brown rather than green and tend to feed at night, hiding in the soil or leaf litter during the day. Loopers (which move with an arching, looping motion) can also be confused with cabbage white larvae, but cabbage white caterpillars crawl normally on all their legs rather than looping.
