Look out for cabbage worms

Earlier this week I spotted some small, white butterflies flitting around in our garden.  They were the easy to recognize adult stage of the imported cabbage worm larva. Now, a few days later,their larvae are voraciously eating our cabbage.

Typical signs of cabbage worm infestation: holes in the leaves and caterpillar droppings called "frass".
Typical signs of cabbage worm infestation: holes in the leaves and caterpillar droppings called “frass”.

Curiously, I haven’t seen any on the broccoli or kale yet, but they will show up there soon too. These pests eat any and all plants in the cabbage family including broccoli, cauliflower, kale, turnip and rutabaga. They are said to attack radishes as well but I’ve never seen it in all my years of gardening. Maybe it’s because our local population would rather eat the other plants if given the choice.

BTW, it’s not the baby caterpillar that makes the choice what to eat, it is its mother. The female butterfly flies all around looking for the ideal spot to lay her eggs so her offspring have the best food to eat. That way they can grow up to be big and strong and healthy. That is good for the cabbage worms but can be disastrous for a garden.

Farmers know that within days a few cabbage worms can chew so many holes into a cabbage that it will be unfit for market. Even in a home garden cabbage worms will ruin large portions of a cabbage.

There are a couple of different species of cabbage worms in our area, one is the imported cabbage worm, the other is the cabbage looper. They are both green and color and do the same damage. Imported cabbage worms are very slow and sluggish when they move. Cabbage loopers move along like inch worms.

If left alone, this young imported cabbage worm will quickly grow and cause lots of damage.
If left alone, this young imported cabbage worm will quickly grow and cause lots of damage.

Both species of cabbage worm are easily controlled by insecticides labeled for chewing insects on vegetables. Bacillus thuringiensis, or Bt, is a favorite worm killer among organic gardeners. It is made up of spores from a bacteria that infects only caterpillars and is harmless to other insects.

Controlling them now while they are still small is much easier than waiting until they get bigger and really start chewing away large chunks of your crop.

Bob

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