How To Get Rid Of Cabbage Loopers


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Are cabbage loopers driving your crazy destroying your plants? Learning how to get rid of cabbage loopers naturally is one of the best things you can do for your garden.

Cabbage loopers are large, fat green caterpillars found on plants in the cabbage family in Canada, the United States, and Mexico that cause terrible damage to cabbage plants. They can be controlled organically with BTK, row covers and other methods but there are simple tips that will make controlling them much easier.

Let’s have a look at what this pest is, the damage it causes and the best methods for controlling it in your garden so you can have a great harvest.

What Are Cabbage Loopers

Cabbage loopers (Trichoplusia ni) are a type of inchworm that feeds on plants in the cabbage family.

The caterpillars grow to be large 1-1/2 inches (3.81 cm) long.

They are a pale green color with a narrow white stripe running along each side. There are several narrow lines running down the back.

How To Get Rid Of Cabbage Loopers text overlaid on a closeup photo of a cabbage looper on a stem

You can easily tell loopers apart from cabbage worms because the looper walks in a typical inchworm fashion where they double up as they crawl along. This is because they don’t have feet in the middle of their body.

It gives them a wobbly appearance when they are moving along, you’d almost think they were drunk and teetering around on the plant.

The adult moths are a grey moth with a V-shaped spot in the middle of each forewing. Their wingspans are 1-1/2 inches (3.81 cm). These moths aren’t commonly seen in the garden as they fly at night.

Lifecycle

Trichoplusia ni, cabbage looper moth
Trichoplusia ni, cabbage looper moth

Moths breed and lay their eggs on the leaves of the plants in the spring. They are a pale green color and domed shaped. You’ll find them in rows on the underside of the leaves.

These eggs hatch in 3 to 4 days and the loopers begin feeding.

They feed on your plants for 2 to 4 weeks going through multiple growth stages.

When finished they make thin silk cocoons that can be found in the undersides of leaves or on the stems. The adult moths will hatch in about 10 days and the cycle will start over again.

Pupae started late in the season will overwinter on plants and debris in your garden.

In Canada and the northern USA, cabbage loopers can have two or three generations in a year, while further south several can easily happen

Damage

Young cabbage looper larvae eat the bottom leaves of the plants.

Older larvae will feed over the entire plant. You’ll recognize the feeding by the large, irregular holes in the leaves.

Loopers also bore down into the middle of cabbage heads. This causes obvious damage to the plant in addition to all the slimy poop they leave behind in the cabbage head.

What Do They Eat?

Cabbage loopers look like inchworms.
Cabbage loopers look like inchworms.

Cabbage loopers mostly feed on plants in the cabbage family but there are other types of crops they will eat too. This includes:

  • Cabbage
  • Cauliflower
  • Celery
  • Collard Greens
  • Cucumbers
  • Broccoli
  • Broccoli Romanesco
  • Bok Chou
  • Brussels Sprouts
  • Horseradish
  • Kohlrabi
  • Mustard Greens
  • Napa Cabbage
  • Radish
  • Spinach
  • Tomatoes
  • Turnips
  • Rutabaga
  • Tatsoi

How To Get Rid Of Cabbage Loopers

Cabbage looper caterpillar
Cabbage looper caterpillar

While cabbage loopers are a nasty pest in the garden there are multiple ways you can control them naturally.

1. BTK

BTK (Bacillus thuringiensis) is the most popular way to organically control cabbage loopers. It is harmless to bees and most insects but can effectively kill all caterpillars that feed on a plant that’s been sprayed with it.

Often called BTK or BT this is a bacteria that is naturally found in soil. Spraying it on your plants won’t harm them but it will kill the loopers that feed on them.

BTK gets into their system when they eat leaves that have been sprayed. Then it disrupts the digestive system of the caterpillar causing it to die.

Start applying BTK early in the growing season so that it can kill cabbage loopers as soon as they hatch and start feeding.

You need to apply it again after watering or if it rains. Follow the directions on your bottle but we normally do a weekly application.

You can get BTK here.

2. Diatomaceous Earth

Another way to get rid of cabbage loopers is by using food grade diatomaceous earth sprinkled over your plants.

This powder cuts and the skin of insects that crawl through it and causes them to dry out. It can also harm beneficial insects though so be careful in how you use it in your garden.

You can get diatomaceous earth here.

3. Hand Picking

If your garden is small, handpicking can be a good option.

Take a little time every few days to look at the top and bottom of your cabbage leaves. Pick off any larva or eggs you find.

Loopers can be drowned in a jar of soapy water or fed to your chickens.

Prevention

Row Covers

Floating row covers or bug netting can be an effective way of keeping cabbage loopers out of your garden.

Since this pest can overwinter in garden debris this method is best used in an area that you haven’t grown cabbage or other plants it feeds on before.

If you practice crop rotation this can be an effective method of control.

Remember to use hoops to hold the cloth up above the plants so the moth can’t lay eggs through the cloth.

Use a bug netting like this one.

Natural Predators

There are many natural predators of cabbage loopers. Parasitic wasps (trichogramma wasps) are their main predator.

Try releasing some into your garden to help control them.

Other predators include lady beetles, spiders, and predatory beetles.

Growing plants that attract predatory insects also helps lower the pest population naturally in your garden.

Dill, cilantro, fennel, yarrow, tansy, cosmos, and scented geraniums are all easy to grow herbs and flowers that are perfect for attracting beneficial to your garden.

Active Time
20 minutes

Total Time
20 minutes

Difficulty
Easy

Instructions

  1. BTK (Bacillus thuringiensis) is the easiest, organic way to kill cabbage loopers on your cabbage plants. This natural soil bacteria disrupt the digestive system of caterpillars causing them to die. For best results start spraying your cabbage plants every 1-2 weeks after transplanting into your garden.
  2. Diatomaceous earth is another easy way to get rid of cabbage loopers. For DE to work, they have to crawl through it so it’s only effective when the caterpillars are on the outsides of your plants. Lightly dust the plants with food-grade DE and remember to reapply it after it rains.
  3. Hand-picking is another good option if you have a small garden. Every few days check the top and bottom of the cabbage leaves for eggs and caterpillars. Remove and dispose of any you find.

How To Prevent Cabbage Loopers

  1. The easiest way to prevent cabbage loopers from damaging your plants is to use row covers as soon as you transplant them into your garden. Use a lightweight row cover or fine bug netting suspended over the plants by hoops.
  2. Planting many herbs and flowers throughout your garden will also help to encourage natural predators to stay. Spiders, ladybugs, and predatory beetles are a big help in keeping an organic garden pest-free.

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