Cabbageworms or cabbage worms or imported cabbage worms are the larvae of the Cabbage white butterfly that feed on cabbage, kale, broccoli, Brussels sprout, collards, kohlrabi, cauliflower, turnips, radishes, mustard greens and rutabagas.
Identify the pests
The butterflies have off-white wings that span about 2 inches wide with 1 or 2 greyish-black spots per wing. They are too pretty to miss!
The butterflies lay their eggs on the undersides of the leaves of the plants their larvae enjoy feeding on! These eggs are yellowish and oval shaped. Keep a look out!
Once the eggs hatch, there’ll be a swarm of small fuzzy velvety green worms/caterpillars that are about an inch long! They chew on the leaves and vegetables of their favorite food!
Signs of an infestation
If you see holes in the leaves of the aforementioned plants and entry holes through the heads of the vegetable you are inspecting, you have a cabbageworm attack! An infestation may be as few as 2 or 3 worms per plant given that these worms have voracious appetites. Be sure to check the undersides of the plant as they love hanging out down under! Also, dark green droppings are a sure shot sign of cabbageworm infestations.
Controlling and Prevention Techniques
Cover plants with a barrier: Prevent butterflies and moths from laying their eggs on your plants by providing a barrier over the plants. The cover should allow sunlight, air and water through but should be fine enough to keep out insects. Light weight nylon nettings, floating row covers and agricultural fleeces are available in the market and will serve the purpose.
Hand picking: The best time to hand pick the worms off is in the morning when they come out for their morning snack! Put on garden gloves and get down to business. The underneath of leaves is their favorite hangout so look there.
The cornmeal method: Dampen the leaves of infected plants. Sprinkle cornmeal, rye flour or a mixture of one part salt to two parts flour on the leaves. The cabbageworms that eat this meal will bloat and die!
Sticky yellow traps: Make your own sticky trap by smearing bright yellow index cards with Vaseline or Honey. Tape the card to a straw or chopstick and stick it into the soil. Voila! It will end up catching beneficial insects too though!
Organic sprays: For serious infestations, consider using an organic insecticide such as Bacillus thuringiensis (BT) which is a bacterium that is known to kill cabbageworms and many other pests. BT has been used as an insecticide for over 50 years and is considered safe for the environment and humans. Use it as given in the directions.
Discard old crops: Dead and decaying leaves and plants are a breeding ground for insects. It would be best to discard them into your composting pit as soon as you see a wilting leaves or after the end of your growing cycle.
Control by using beneficial insects: Insects such as yellow jackets, ground beetles and barconid wasps will help you in your battle against cabbage worms. The barconid wasp is especially effective as they will feed on these worms all day long! Trichogramma wasps, also called ‘stingless wasps’ parasitize the eggs of cabbageworms, hence are widely used as a means of biological control of pests. You can mail order these beneficial insects but it is highly recommended that you seek advice from a specialist from your area before letting them loose in your garden!
Companion planting: Plant anise, garlic, onions, sage, rosemary and mint near the plants that get affected by cabbage worms. They are said to deter cabbage worms, although I must warn that some research shows that this is not beneficial!