Uninvited Guests for Dinner: Managing the Cabbage Worm

Backgrounder

Would you share your dinner with someone who has 20 legs? Would you share your dinner with someone who steals from you? Probably not, but this may be happening to you right now. In your garden the hungry cabbage worm (Artogeia rape or Pieris rapae) is busy eating part of your dinner.

The cabbage worm eats cabbage, collards, cauliflower, broccoli, brussel sprouts, mustard, kale and other plants in the cabbage family. It also feeds on turnips and radishes. It has a velvety skin that is the same green colour as the leaves of many plants. It has one or more thin orange or yellow stripes down its back, and is about half the length of your thumb in size.

The cabbage worm spends much of its life in the ground. When it gets hungry it climbs out of the soil and begins to eat your plants. The hungry worm eats large holes in the leaves of your crops and eventually eats into the middle of the plant.

After 2-4 weeks it has eaten enough and it returns to the soil. One or two weeks later it comes out of the soil again as a white butterfly. You can sometimes see these butterflies flying around your garden. They are mating. After they mate, they lay eggs. From these eggs come another generation of cabbage worms that will eat even more of your crops. The cabbage worm can have many hungry offspring every year.

But there are lots of things you can do to stop sharing your dinner with the cabbage worm. Many of these things are safe, easy, and don’t cost much.

Rotate your crops

One of the best things you can do to prevent any pest from continuing to eat your dinner is to rotate the crops in your vegetable patch. For example, you could plant maize or carrots where you planted cabbage last season. If you want to grow cabbage plants, plant them where you planted maize or carrots last season. When the next generation of cabbage worms comes out of the soil, they will not find any food that they like and will not survive.

Pick the worms by hand

Cabbage worms spend part of their lives in the soil around plant roots. If you till the soil around these plants several times at the beginning and end of the growing season, you will expose the worms to the air, and they will dry up and die. If you miss some, and they start eating your plants, the easiest thing to do is to pick the worms off by hand. Then you can collect and burn them.

Trap the worms

Here is a way you can stop cabbage worms from laying eggs on your plants. When you see white butterflies flying around your cabbage plants, place sticky traps among the plants. You can make a sticky trap from a flat piece of wood, cardboard, or even stiff plastic. It can be any size you want. Paint its surface yellow, then cover it thoroughly with glue. You will need to cover it again with glue every two weeks. Then attach the trap to wooden stakes placed among your cabbage plants. As butterflies fly around your plants laying eggs, they will stick to the trap.

Mix your plants

Here’s another good method to manage cabbage worms. Many people will avoid a strong smell, and cabbage worms are the same. They stay away from certain strong-smelling plants. Examples of these plants are: onion, garlic, tomato, sage, tansy, mint, hemp, hyssop, and rosemary. If you grow these plants around your cabbage plants, you will scare away many cabbage worm butterflies.

Spray your plants

There are a number of safe and easy-to-make sprays that can reduce the number of cabbage worms in your garden. For example, you can make a spray from garlic. Boil five or more bulbs of garlic in a gallon of water. When the water smells strongly like garlic, let it cool and remove the garlic. Spray the liquid over the plants you want to protect.

A spray made with neem seeds will also keep cabbage worms away. You will need a double handful of neem seeds. Remove their shells and grind up the seeds. Put the seeds in ten litres of water, and let them soak overnight. The next day, filter the liquid through a sieve. Then spray it on your plants. The plants will change colour a little, but they are still safe to eat.

Use other insects to control pests

Here’s one more method of control that is becoming popular. If you can encourage other insects that feed on cabbage worms to live near your plants, they will destroy many of the pests. For example, there is a tiny wasp called the trichogramma wasp that lays its eggs inside cabbage worm eggs. When the wasp eggs hatch, the newly-hatched wasps eat the cabbage worm eggs. You can attract these wasps to your garden by growing plants which they feed on. Some examples of plants which will attract them are mint, dill, parsley, and catnip. These wasps are very sensitive to pesticides, so be careful not to use any chemicals that will kill them.

If you think there are still some cabbage worms hiding in your crops, you can sprinkle the whole plant with a mixture of one part salt and two parts flour. If you shake this mixture on the plant after it rains, cabbage worms will eat it, then become bloated and die.

Hopefully, after you try these methods, you will no longer have to share your dinner with the cabbage worm.