What do they look like? The small white cabbage butterfly (Pieris rapae) flies around the garden at this time of year looking for places to lay her eggs - usually on the underside of the leaves (see photo). Cabbage white butterfly is white with distinct black spots on the wings and is 40mm wide. The cabbage caterpillar is soft blue green and it usually feeds at night and remains still and well camouflaged during the day, lying along the mid rib of the leaf (see photo). There are many types of caterpillars which are usually the larval (caterpillar) stage of moths such as cabbage moth (Plutella xylostella) which is grey and small and is10mm across. The caterpillar of the larval stage of this moth is green-brown.
What do they do? If you see the white butterfly hovering over your cabbage patch, be warned, she is laying eggs! The butterfly pupates from this caterpillar, which can eat very quickly and cause lots of damage to developing cabbages, lettuce, broccoli, and spinach. They both start eating the outer leaves before moving to the inner heart of the cabbage. It is 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. You should see eaten leaves and lots of green/black droppings everywhere (see photo).
Can we live with them? No
Control Spray with a registered organic products such as 'Success' or 'Dipel', which are biological controls, every 7 days or pick them off and feed them to the chooks! Maybe a butterfly net would be handy or an old squash racquet (see photo)! Or use pyrethrum spray. Yellow sticky traps from 'Outdoor Complete' are also effective at controlling the adult butteflies.
Eggshells! With a black permanent marker, draw two spots on and eggshell then perch it on a stick amongst the veggie patch. The white of the eggshell with black spots vaguely resembles the Cabbage White Butterfly. This is often enough to make the Butterflies turn around and lay their eggs elsewhere.