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Growing Pest-Free Cabbage Naturally: Effective Cabbage Looper Control

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If you've given up growing cabbage in your garden because it always gets infested with cabbage loopers (Trichoplusia ni), you aren't alone. Many home gardeners get discouraged and think their only solution to combat these garden pests is to stop growing cabbage. There are several natural options for keeping these pests from devouring your plants. 

Cabbage Looper Life Cycle

Understanding the life cycle of the cabbage looper helps you break the breeding cycle and banish them from your garden. The first sign that they have invaded your area is generally the appearance of little white moths that flutter in your garden. These are the adults looking for host plants to lay their eggs. They typically appear in early to mid-summer, depending on your location.

Once the adults find a suitable host, like your cabbage plants, they lay green, dome-shaped eggs on the foliage of your cabbage. These tiny eggs hatch within 3 to 4 days, and then emerge as larvae. The larvae looks like a tiny, green inchworm with a white stripe down the sides of the body. These larvae begin feeding by boring into the head of your cabbage, where they spend the next two to three weeks feeding. They eventually emerge and pupate in a webbed cocoon on the underside of leaves. New adults emerge in about 10 days and the cycle begins all over again. 

Physical Barriers

Floating row cover suspended over your cabbage plants creates a physical barrier that prevents the adults from laying new eggs on your cabbage plants, but to be effective it must be installed before the first eggs are laid. This spun polyester fabric allows light and water to reach your plants, while preventing the cabbage looper moth from getting close enough to do any damage. Because cabbage do not rely on flying insects for pollination, they will thrive and grow to maturity under the cover of a floating row cover. However, the row cover must be complete with no open spaces for the moth to access your plants. There are three easy ways to do that.

  • Build a box frame with lightweight wood that fits over your garden row and cover it with row cover. Set it over the plants.
  • Place a vegetable cage over the cabbage plant and cover it with row cover. This works well if you're growing just a few plants.
  • Make a hooped row cover and cover it with floating row cover. Set it over the row before the first cabbage worm moths appear.

Companion Plants

Many gardeners take advantage of companion planting to repel garden pests, including cabbage loopers. This technique involves interplanting your cabbage with plants known to repel insects or planting a row of companion plants beside your cabbage. Although it is not known how these plants work, many believe the scent of the companion plants confuses the insect pests by masking the scent of your cabbage.

  • Marigolds: These pungent little flowers are thought to repel a host of harmful insects in the garden. According to Hobby Farms, this includes the cabbage looper.
  • Thyme: This herb serves double-duty in the cabbage patch, as it repels the cabbage looper and provides you with a versatile herb for cooking. For a change of pace, try lemon thyme and use it to season your coleslaw, too.
  • Mint: Mints are aromatic herbs that are thought to repel cabbage worms, but they are also invasive perennials. If you choose to grow mint in your cabbage patch, grow it in pots or remove both ends of a gallon tin can (the kind canned veggies come in) and insert it to the rim in the ground. Grow the mint plant inside the can. This prevents the roots of your mint from spreading to other areas of the garden.

Organic Pesticides

Many gardeners are hesitant to apply chemical pesticides to cabbage because it must be applied directly to the edible part of the plant. Fortunately, there are organic controls effective against cabbage loopers that you can make yourself.

  • Garlic & Fish Oil Spray: A mixture of 1% garlic juice, 1% fish oil and 98% water has been shown as effective as commercial pesticides in a study conducted by Alabama's Auburn Univeristy.
  • Ground Red Pepper: A mixture of ground red pepper and water applied to the cabbage plants is effective for killing the larvae. It is thought to work as a stomach poison to the caterpillars. Mix one teaspoon of ground red pepper to one quart of water and spray your cabbage plants to control the larvae.

Cabbage loopers can be a challenge once they get out of control, but you don't need to give up growing cabbage in your garden. Try your hand at these natural methods to banish this insect pest from your garden. If you still have trouble with garden pests, click here for info.