Cabbage Moth Caterpillars

It doesn't take long from the time you put in your cabbage, kale or broccoli (actually anything related to cabbage) before you will have to deal with the offspring of the Cabbage Butterfly. Yep, that small white butterfly that has been flitting about visiting your cauliflower, Brussels sprouts and kale is evil. Well, at least her children are. A few weeks after she's stopped by, you will start noticing holes in the leaves of your plants. A quick inspection may reveal nothing, but if you look closely, underneath the leaves, you can usually find the caterpillar. They can be difficult, really difficult, to see at first. For a week or so, they are only about 1/4" or length. But as they feed, they grow quickly. And in about two weeks or so, you will find the green caterpillar about the size of the one pictured below.

For small populations (when you have only minimal damage) you can merely pick them off and squish them. But for larger infestations you need something more. One of the best ways to stop caterpillars from feasting on your cabbages is to stop them in the first place. Placing a lightweight row cover over your plants right after planting will prevent adults from being able to lay their eggs on the leaves. This however can be problematic in warmer climates because it can raise the temperature too much should we get a heat spell in October. It can also be unattractive and annoying to move out of the way should you want to tend your crop.
If the row cover or the manual method of dispatching the caterpillars doesn't appeal, you do have another organic option; bacillus thuringiensis or BT. Sold under the brand name by Safer called Caterpillar Killer, or Garden Dust (which is OMRI certified), BT is the natural choice for controlling leaf-eating caterpillars. Caterpillars stop feeding shortly after eating foliage sprayed with Caterpillar Killer and die within a few days. Caterpillar Killer does not harm honey bees or beneficial arthropods and does not harm earthworms.