Cabbage White Butterfly
Pieris rapae
Cabbage white butterfly caterpillars chew ragged holes in brassica leaves and can rapidly defoliate seedlings and mature crops.
Cabbage white butterfly is a common pest of brassica crops and ornamentals across Australia. The adult is a white to cream butterfly with a wingspan of around 40–50 mm, with one or two black spots on each forewing and black wingtips. Adults are active fliers seen fluttering around brassica plantings during the day, feeding on nectar and laying eggs but causing no direct plant damage themselves.
The damaging stage is the larva. Eggs are laid singly, usually on the underside of leaves, and are small, pale yellow and spindle-shaped. Young caterpillars are pale green and difficult to see against foliage, while mature larvae grow to about 25–30 mm, are velvety green with faint yellow stripes along the body, and are covered in fine short hairs. Larvae are found on leaves, often tucked into the heart of the plant or along leaf veins, and pupate as a green to brown angular chrysalis attached to stems, leaves or nearby structures.
This pest is present in all Australian states and is active for most of the year in warmer regions, with peak activity in spring and autumn when temperatures are mild. Multiple overlapping generations occur through the growing season, so eggs, larvae and adults are often present at the same time.
Management relies on regular crop monitoring, especially checking leaf undersides for eggs and young larvae before populations build up. Physical exclusion using fine insect netting over susceptible crops is effective in preventing egg-laying. Encouraging parasitic wasps and other natural enemies helps suppress populations, and good crop hygiene, including removal of old brassica plants and weeds from the Brassicaceae family, reduces breeding sites between crops.
How to identify
- Leaf damage: irregular holes and ragged chewing, starting on outer leaves and progressing inward; young seedlings can be skeletonised or killed.
- Heart and head damage: larvae often burrow into the heart of cabbages and similar crops, leaving frass (droppings) and damage that is not visible from outside until the head is cut open.
- Frass: small dark green to black pellets on leaves or caught in leaf folds indicate active feeding nearby.
- Confirming the pest: turn leaves over and inspect the undersides for pale yellow spindle-shaped eggs or green hairy caterpillars; check leaf axils and the plant heart where larvae often hide during the day.
- Lookalikes: diamondback moth larvae cause similar shot-hole feeding on brassicas but are smaller, more slender, pale green, and wriggle vigorously when disturbed rather than remaining still like cabbage white caterpillars. Cluster caterpillars and other loopers can also be confused with cabbage white larvae; loopers move with a distinctive arching motion due to reduced middle legs, which cabbage white caterpillars lack.
