About the Cabbage Caterpillar

There are three common caterpillars which choose brassicas as their source of food:

• Cabbage Moth (Mamestra brassicae)
• Large Cabbage White Butterfly (Pierris brassicae)
• Small Cabbage White Butterfly (Pieris rapae)

The most conmmon one is the Small Cabbage White Butterfly and it certainly does the most damage in its caterpillar stage.  This damage occurs between April and October because each of the varieties has two or more geneartions strecthing from Spring to Autumn.

What plants do they attack, when do they emerge and what is their cycle?

In mid-spring the Small White Butterfly adults appear and lay single eggs on the cabbage, cauliflower, brussel sprouts, kale and kohlrabi, swede and turnip leaves.  These eggs are oblong, yellow and ridged along their length and they hatch within 5 days of laying (depending on the weather conditions) into bright green velvety caterpillars.  In the beginning they feed on the outer leaves, but as they grow they move towards the heart of the brassica.  After about two weeks they are 2,5cms (1") in length and it is at this stage that they leave their food plants to pupate into the chrysallis stage from which more butterflies and moths will emerge. They attach themselves to a vertical surface like a fence or wall.  The final generation of the season over-winters as a chrysallis. The Large White Butterfly lays it eggs in batched of 10-20 and these hatch into yellow and black slightly hairy caterpillars in about two weeks.  These caterpillars will feed for a month and reach up to 50mm in length before pupating

How can they be identified?

• the Cabbage Moth is greeny-brown all over with no "hair"
• the Large Cabbage White has a yellow body with dark black markings all over the body
• the Small Cabbage White is pale green all over with a velvet appearance

What does the damage they do look like?

• both outer and inner leaves are eaten
• the holes are shapeless and irregular
• once the heart is tunneled into the plant will begin to rot and become spoiled with the excrement

Treatment for Cabbage Caterpillar

• inspect the undersides of leaves and remove any egg clustersi
• caterpillars can be removed by hand when young and on outer leaves
• protect the plants with netting - Wondermesh
• use Nemasys Codling Moth and Caterpillar Killer - a natural parasite of the Cabbage caterpillar (Steinernema carpcapse) which is completely safe to use on brassicas and will not harm any other wildlife nor render the vegetable unfit for human consumption
• encourage insectivorous birds within the garden by using bird feeders in winter and nest boxes in spring
• avoid planting colourful, high nectar plants near to the cabbage patch as this will increase adult butterfly activity
• chemical spraying can be done with products containg Pyrethrum, Rotenone or Bifenthrin but this needs to be done with care as plants cannot be sprayed near to harvesting as well as the environmental effect on other beneficial wildlife