Dealing With Cabbage Caterpillers

There are three common culprits, all of whom become these nice, gorgeous and oh-so-innocent (not!) butterflies: the nasty caterpillars of the large "cabbage white butterfly" and "small cabbage white butterfly" , and the "cabbage moth". All three may be present at the same time and tend to attack mature plants. Caterpillars of cabbage moth and small white butterfly are more damaging as they bore into the hearts of cabbages, whereas the yellow and black caterpillars of the large white stay mostly on the outer leaves.

Here is a picture from the Royal Horticlultural Society of a cabbage moth caterpiller. Notice, they chew right into the mature leaves of the object plant.

The life cycle is as follows. The adults appear in mid-spring and lay single eggs on the leaves of cabbage, cauliflower, Brussels sprouts, kale and kohlrabi. The eggs are yellow, oblong and ridged lengthwise. They hatch in around 5 days depending on weather conditions. Initially they feed on the outer leaves, but as they mature, they tend to go for the heart leaves. They reach about 2.5 cms (1 inch) in length after a couple of weeks. Around this stage they pupate into a chrysalis and it is from these chrysalis that more butterflies and moths will emerge. The final generation of each year over-winters as a chrysalis.

Prevention includes identifying the butterflies themselves who are the culprits who have the eggs. If they are seen, it is often wise to cover cabbages, kale, cauliflower and etc. with a fabric of some kind, simply to keep them from laying eggs.

As with all caterpillers and also as in the case of slugs and snails, the primary method of controlling them is to simply pluck them with your fingers and give them a good squish. Otherwise, put them in a container but, by all means, get them and keep them out of the garden. Deal with any eggs you see the same way. Scrape them off or remove the offending leaves.

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.