Is It A Cabbage Moth or Cabbage Butterfly?
By Penny Ossowski
Well it could be either. Both attack our brassicas. The cabbage moth (Plutella xy-lostella) is about 10mm across and greyish in colour, while the cabbage butterfly
(Pieris rapae) is about 45 mm across, white in colour with a couple of black spots. The female has 2 black spots and the male 1 on each wing. Both lay their eggs on the underside of leaves and while their caterpillars are different both are voracious feeders destroying many a small plant and leaving larger plants a mess.
The cabbage moth caterpillar is green-brown and about 10 mm long when fully grown while the cabbage white butterfly caterpillar is velvety green and about 25 mm long. There are several organic ways to try to keep them away from your valuable vegetables. A good population of birds will pick off a lot of caterpillars, companion planting with Sage, Rosemary or Pennyroyal, inter cropping with different shaped plants (to confuse them) such as beans and celery will all help, alternatively you can spray. All sprays should be sprayed onto the underside of the leaves as this is where the butterfly/moth lays its eggs. Some sprays you can use are Molasses spray below or 'Dipel' as recommended by John or why not collect together a handful of those caterpillars, blend them with 2 cups of water (or milk), let it stand for a few hours then spray (I have never tried this one but have been told it works well, but not in my food processor).
Eden Seeds carries cabbage seed online for home gardeners. Many Heirloom cabbage varieties are available for Australia wide distribution.