Arrival of Cabbage Worms & What to Do About Them

Posted on 04/08/2020

Lovely Weather = Hello Garden Pests

You may have noticed pretty white and pale yellow butterflies arriving in your garden or yard. These "cabbage white butterflies" enjoy Spring and Fall weather. They loop about and land softly on leaves to deposit eggs which then hatch into tiny caterpillars also called "cabbage worms." They are not technically worms at all, and they can destroy an entire kale plant in a week. You will find their eggs are on the undersides of the leaves, but you can find them on the top sides as well. A brown moth, referred to as the "cabbage looper" also visits your greens when you are not looking - doing the same egg-laying deed. We can find these caterpillars on most any plant in the cabbage family (kale, collards, broccoli, cauliflower, mustard) and sometimes on lettuce, spinach and Swiss chard.

Here is a clip of a cabbage butterfly landing on a flower, looking for nectar. The caterpillars are, of course, the larval form of these lovely butterflies. As you can see, they are pollinators too. 

When the egg hatches, a practically invisible caterpillar emerges. It has breakfast of a microscopic sort from the leaf. Then it has lunch, afternoon snack, dinner, midnight snack, and by breakfast again the caterpillar is three times its original size. This is where the problems start. 

The egg is a tiny oblong speck on the leaf below. 

Below is a caterpillar that has been around a day or two. Look just above the thumb.

Below is a more mature cabbage looper caterpillar. 

 If left unchecked, this is what happens overnight! See if you can spot the caterpillar in the picture.  Kids love the challenge of trying to spot them. 

Controlling the Damage from Cabbage Worms

1. Daily inspection of your leaves - top and bottom sides. 

Kids are great at scouting for pests once they get the hang of spotting them. The eggs are tiny and the caterpillars are camoflauged. Finding them is a fun challenge. Once found, simply wipe them off with fingers. If the caterpillars are big, have kids pick them off and put into a bucket for you to "deal" with. Backyard chickens love them, but if no chickens, mush them and move on. 

2. Sprinkle Bt powder or spray Bt liquid.

Apply on the leaves every 5-7 days and after a rain or overhead watering. This is a bacteria that is harmful to caterpillars but benign to people, pets and other insects such as ladybugs. 

It is astonashing to see how quickly these hungry caterpillars grow. We recommend letting one or two live just to watch this process -- intervening before it is too late of course. In school gardens, we always rely on scouting and hand removal first. If the cabbage butterflies and cabbage looper moths are out in numbers before heading into the weekend or a break, we may use Bt to help keep the caterpillars at bay while we are not in the garden. 

OKC Harvest practices organic gardening in our outdoor classrooms. This means we rely on preventative measures as our first line of defense against pests, and we teach our students to think through choices with the entire ecosystem in mind.

 

OKC Beautiful is happy to share these resources for organic gardening in our region. 

Natural Control of OK Garden Pests Part I

Natural Control of OK Garden Pests Part II

These guides were compiled by OKC Harvest Director, Kat Gant. The information comes from her 20 years of farming and gardening experience, including 10 years of teaching gardening to children and adults. She will tell you that all gardening know-how is gleaned from working with other amazing growers, farmers, gardeners and wise ones over the years. Her philosophy, which we impart to our students through the OKC Harvest program, is to employ a holistic, ecological approach to building healthy soil and to always act with the entire garden community in mind.