Garden Battles: Cabbage Worm

cabbage worm butterfly on kale

I was harvesting my lettuce when a flash of white flitted by the kale. My heart stopped: it was the dreaded cabbage worm.

Last year, I spent an enormous amount of time fighting imported cabbage worm. The white butterflies, the adult form, are attracted to members of the cabbage family. In my garden, that means mustard and kale. The small, white butterflies lay yellow, bullet-shaped eggs under the leaves. Within a few weeks, the larva, the disgusting green worms, decimate leaves and stems. They then pupate and more adults emerge so within a growing season there are several generations. Surprisingly, they can continue all year long on my property in Northern Virginia.

cabbage worm butterfly on lettuce

At first, I tried picking the worms off but quickly concluded that: first, it’s gross; and second, it’s easier said than done. It is difficult to pick them up on a continuous basis because we are all busy.  It seems eggs are always hatching, larvae are always present from very tiny to very large, and the green color of the worm blends in with the green leaves.

I know the other recommendation is to use row covers but I live in a traditional suburban home and my kale and mustard plants are in pots on the deck or tucked in the landscape, not in rows. I do not have the type of vegetable garden where there are rows of one crop.

Finally, I resorted to Thuricide®, a liquid form of Bacillus thuringiensis (Bt), thinking that I would just have to spray once or twice. Bt is a bacteria that kills the larvae so it is a non-toxic, biological insecticide. However, it got to the point where I felt that all I was doing was spraying instead of growing and eating.

By the end of the year, I was fed up and vowed not to grow kale and mustard again. Then I thought what if I grew the colored mustards as a winter annual in a container? For sure the cabbage worms could not be active in the winter.

But yes, Virginia, they were very active in the winter and ate the mustard as if it were a summer delicacy. Do you have this problem in the garden and if so, what do you do to battle the cabbage worm?