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Managing Cabbage Worm

It’s a lovely spring day and you are sitting in your garden admiring your burgeoning broccoli plants. A little white butterfly flits by in the sunshine. Could this little darling be the voracious chomper that was secretly chewing on your brassicas as a caterpillar?!

Brassica seedlings you have planted in the spring garden are susceptible to chewing insects that are just as anxious to eat them as you are. They might be visited by a common pest like the imported cabbage worm, also known as the cabbage butterfly. Its Latin name is Pieris rapae.

You can take steps to address a pest like this organically, with a few simple approaches.

  • Know thy pest. The imported cabbage worm butterfly is white or cream-colored, with 1-4 spots on its wings. It has an irregular flight pattern. It lays pinhead-sized eggs on the undersides of brassica leaves. The eggs are cream or yellow-orange. The resulting caterpillar is green with white markings (or can be purple if feasting on purple cabbage) and leaves messy frass (droppings) on the plant. Learn these types of details for any pest you see attacking your veggies.
  • Learn how it harms the plant. In the case of the cabbage butterfly, it’s the caterpillar that does the damage. You’ll see holes in leaves and leaf edges from its feeding. This is primarily a problem on younger plants.
  • Practice hand disposal. If you can, crush the eggs, caterpillar or butterflies. This is often all home gardeners need to do. You’ll be helped by beneficial insects such as parasitic wasps; different species parasitize the cabbage butterfly at different life stages.
  • Erect a barrier. Use of a floating row cover (aka Reemay) can be an effective barrier to cover large plants or a large bed of seedlings, because it will keep the butterflies from laying eggs on the leaves. Cover the entire planted area loosely and anchor it securely on the ground with stones or boards, or by digging the edges under the soil at the perimeter of the bed. It is important to apply the floating row cover before there are pupae present in the soil.
  • Rotate your crops. Plant your  brassica plants in a different location each season. This rotation will confuse and disrupt any ongoing generations of the cabbage moth and other pests from easy access to their favorite foods. There are many plants in this family group including cabbage, broccoli, cauliflower, kale, collards, Brussels sprouts, mustard, radish, turnip, kohlrabi, rutabaga and more!