This afternoon I found something awful in my garden; a cabbage leaf, the underside of which had an infestation of cabbage looper eggs!
This is intolerable! These eggs will hatch into voracious green caterpillars that have the potential to destroy my already meager early cabbage crop. And grow up to be cabbage looper moths that will continue the cycle next year. The control of cabbage worms and cabbage loopers is the same. To combat these little munchers I’m taking several steps.
First let me give you a little background on these destructive insects. The cabbage looper (Trichoplusia ni) is a common and destructive insect that is most often found on cabbage-family crops of the Brassica oleracea family. These crops include: broccoli, cauliflower, cabbage, Brussels sprouts, kale, collards, and kohlrabi. You may know cabbage loopers by the name “inch worm.” They are large larvae 1 1/2 to 2 inches long. They are a pale green color with a narrow white stripe along each side and several narrow lines down the back. The adult cabbage looper moth is a nocturnal gray moth with about a 1 1/2 inch wingspan. The moth lays pale green eggs on the underside of leaves. The eggs hatch into the worms and eat and grow and eat more. The more cabbage looper larvae grow, the more they eat, devouring three-times their body weight in plant material a day. They do the most harm during the last few days of their development.
Cabbage looper larvae
Adult cabbage looper moth
The imported cabbage worms (Pieris rapae) are the larval form of the Cabbage White butterfly which have white wings with one or two black spots per wing). The worms are velvety green with a narrow, light yellow stripe down the middle of its back and sport many short, fine hairs. These worms tend to feed closer to the center of the plant. The adults are white or pale yellow butterflies with a 1 – 2 inch wingspan and three or four black spots on their wings. From early spring to late fall you’ll see these butterflies fluttering around your garden.
In my garden I’ll transplant some established parsley and, when my coriander (cilantro) seedlings are strong enough they’ll also go in my cabbage and broccoli beds. I’m also going to start some dill seeds to move to the cabbage and broccoli beds when the seedlings are big enough.
I’m not going to use any chemicals because they’ll also kill the beneficial insects like predatory wasps that eat the eggs of these worms. I’ve encouraged birds to come to the garden by planting flowers that they find attractive and they’ll eat the worms.
Another way to control these pests is to allow chickens and/or ducks into the garden to gobble up the worms. Unfortunately chickens especially, can do a lot of damage themselves. Both ducks and chickens will eat the worms but also tender young plants. Chickens may scratch up seedlings. If you let them into the garden it’s best to wait until plants are mature and less likely to be destroyed accidentally.
If you see worms you may want to apply Bt-kurstaki to the leaves where you’ve seen them. This is a naturally occurring soil bacteria and it will kill the worms as they feed on the leaves. Another option is spinosad which doesn’t persist in the environment the way the Bt-kurstaki will. You can harvest crops one day after applying to your vegetables. Tansy tea has also been reported to be effective in preventing moths from laying eggs on leaves sprayed with the brew. Planting tansy near your cabbage crop may also be helpful. Cabbage helps tansy thrive and tansy deters the moths.
To help keep any moth pupae from overwintering in my garden and emerging next spring I’ll remove and either bury or throw out any cabbage family debris. I’ll also make sure the edges of my garden are cleaned and any grass is cut short. This will eliminate another spot the pupae can hide out over the winter.
Whether it’s for soups, coleslaw, casseroles or other recipes I’m going to do everything I can to ensure I have a large crop for both summer use and for my root cellar.
How do you fight vegetable eating worms in your garden?