First in an Occasional Series

I was in my garden yesterday picking peas when something out of the ordinary caught my attention. I saw a bunch of small green balls at the base of a leaf on one of my broccoli plants. I recognized it as caterpillar frass (excrement).

Caterpillar Frass

To be a successful vegetable gardener, especially if using organic techniques, you need to get familiar enough with you garden to notice when something is suddenly amiss, as in this case

Once I noticed the frass, I then saw that much of the leaf where I found it had been eaten away.

Broccoli Leaf Eaten by Cabbage Worm

This set me to look for the culprit, which turned out to be a Cabbage Worm, which is not a worm at all but a caterpillar, the larval form of a moth. Luckily, this particular specimen was fairly large, over a 1/2 inch long, because Cabbage Worms are almost exactly the same color as the leaf and hard to see when small. I apologize for not having a picture of it, but my instinct to remove the caterpillar kicked in before I thought of writing this blog. Here’s a  good picture I found.

Cabbage Worms

Once I found one Cabbage Worm, I stared looking for more, as bugs almost never appear singly and Cabbage Worms can quickly devastate a crop. Sure enough, I found plenty, all much smaller and having done less damage. So I started removing them, just hand-picking and throwing them out into lawn far enough that they couldn’t make it back to the plants.

Small Cabbage Worms on Broccoli Leaf

I was surprised to find the Cabbage Worms on my plants as I’ve only ever seen them late in the summer, in August and September. Of course, I’ve never grown spring Broccoli either (always learning something).

Cabbage Worms will attack all members of the Cabbage family including cabbage, broccoli, Brussels sprouts, kale, kohlrabi, turnips, etc. For controlling them once they appear, I recommend hand-picking because the caterpillars aren’t gross to touch and it’s has the smallest effect on the environment, a key concept in Integrated Pest Management (IPM- see my garden planning posts). If you can’t bring yourself to touch them I recommend using BT spray which you can purchase at most garden centers. BT (Bacillus thuringiensis) is a naturally occurring bacterium that will kill caterpillars when they eat it.

Best, however, is prevention. In early to mid-August every year, in anticipation of Cabbage Worms, I put row covers over my cabbage family crops. This keeps the adult moths from laying their eggs on the plants. If you do use row covers, you should be sure to check under them every few days at least to see if something else is attacking them. Last year I neglected to do that and wound up with a huge aphid infestation on my turnips.

I’ll be back with more bugs as they appear in my garden, probably Colorado Potato Beetle will be next.