Battling Cabbage Moths

If you enjoy growing things like kale or cabbage you may be in for a battle with cabbage moths. In Southern Ontario, the innocent-looking small white butterfly or moth can wreak havoc when growing brassicas. The female moths lay their eggs on the underside of brassica leaves, these eggs then hatch into small green caterpillars which can devour your brassica plants. In this post, I’ll cover some of the strategies to help you with battling cabbage moths.

What is a Brassica?

A brassica is a genus of plant which includes varieties such as:

• Kale
• Cabbage
• Kohlrabi
• Brussel sprouts
• Broccoli
• Cauliflower

What is a Cabbage Moth?

A cabbage moth is a white moth that is commonly seen around Southern Ontario. The female moths lay their eggs on the underside of brassica leaves, these eggs then hatch into small green caterpillars which can devour your brassica plants very quickly. The tell-tale sign of a cabbage worm is the edge of the leaves will be chewed, like in the image below. They can be difficult to find and are often hiding on the bottom side of the leaves.

How to Prevent Cabbage-worm Damage

There are a few different ways you can prevent cabbage worms.

• Hand-picking – Depending on the population of cabbage moths, monitoring your plants on a regular basis and handpicking any cabbage worms may be enough. In my experience, the cabbage worms were faster than I could keep up. I also did not enjoy the idea of missing one on my curly kale and adding it to my salad.
• Insect Netting – Covering your brassica plants with insect netting can be very effective. This could be done with a floating row cover, however, I’ve found this insect netting from Dubois more durable and has lasted many seasons. I use the insect netting in combination with these hoops from Lee Valley. They are easy to install/move around and can be used for season extension also.
• BTK Insecticide – Bacillus thuringiensis is an insecticide which kills any caterpillar which eats it, however, is harmless to other insects or humans. When spraying your plants with BTK, you need to be sure to cover all surfaces of the plant. It will also need to be re-applied after rain or if you water with a sprinkler.

In my Garden

I have found insect netting to be the most effective way for me to be sure I’m not eating cabbage worms. It is fairly hands off which allows for things like vacation and isn’t impacted by the weather. I occasionally will spray BTK if I find signs of caterpillars from a moth that somehow made it past the netting however this is pretty rare.

I hope you find this helpful, let me know if you have any questions in the comments below.

Happy Gardening!