The cabbage worm is a common garden pest. Keep an eye out for them in your garden & head them off at the pass with these tips…
If you grow brassica crops (cabbage, kale, kohlrabi, broccoli, cauliflower, etc.), you’ve probably had a run-in with the hungry cabbage worm.
Cabbage worms – or cabbage caterpillars – are the larvae of a few different species of moth. The most common in our area (mid-Ohio) is the imported cabbage worm, the larvae of the cabbage white butterfly. There are several other species that also enjoy feeding on brassica crops, including cabbage loopers, cross-striped cabbage worms (we also have these), and the larvae of the Diamondback moth. Most of these caterpillars are green, with the exception of the cross-striped cabbage worm, which has black, white, and gray stripes, and a green or yellow belly.
The Cabbage Worm Life Cycle
Adult moths of all cabbage species lay scattered eggs on the undersides of the leaves of your plants. While visible to the naked eye, these tiny eggs are often pale yellow, white, or greenish, making them difficult to spot. Upon hatching, the little caterpillars immediately begin feeding on the leaves of your crops. You often can see the droppings they leave behind before you see the worms themselves because their camouflage is excellent.
Late in the season, hatchlings inside the bases of cabbage or heads of broccoli or cauliflower may flourish unseen, eating away at your vegetables while leaving their droppings behind. Once they have come of age, so to speak, the caterpillars will make a small cocoon (often on the underside of leaves or in a stem crevice), and pupate there until it is time to hatch into an adult moth and begin the cycle again.
Cabbage worms can be incredibly destructive, sometimes stripping your plants down to just the leaf skeletons in a matter of days with a bad infestation. They also leave droppings inside the heads of cabbages and broccoli, making them difficult to clean when it’s time to harvest and eat them yourself.
Prevention is the Best Medicine:
When it comes to pests, cabbage worms are no exception: it’s best to try to prevent them from gaining a foothold on your crops in the first place.
The good news is, this isn’t difficult when it comes to cabbage worms. Using fine garden netting or mesh is a great way to protect your brassicas from cabbage moths. As long as you cover them as soon as you plant them outdoors, you can keep them covered until harvest time, preventing adult moths from laying eggs on your crops. (Unlike other types of crops, you won’t need to uncover them for pollination, so this makes it a simple and effective method of pest prevention.)
You can also plant plenty of flowers and blooming herbs around your cabbage patch to provide a good supply of nectar for beneficial predatory insects, such as paper wasps, yellow jackets, and shield bugs, all of which eat caterpillars. Birds may also be helpful for controlling caterpillars including the cabbage worm.
Another trick is to try planting red or purple varieties. Cabbage moths look for green leaves to lay their eggs on, so they are less attracted to darker-colored plants. (As a bonus, some evidence suggests these varieties also contain more antioxidants and are healthier for you as well!)
Keeping a close eye on your garden is the best way to spot a cabbage worm infestation early on. Check your plants regularly for signs of droppings or holes in the leaves of your cabbage family crops. If you spot them in time and there are only a few, you can just pick the caterpillars off by hand. (Chickens love them as a tasty snack!)
If you are unable to cover your plants with netting, or you don’t get them covered in time, you may need to resort to a blanket treatment of B.t., a bacterial pesticide that is approved for organic gardening. B.t. (bacillus thuringiensis) affects only caterpillar pests, and does not harm beneficial insects, including bees.
You will need to apply it in between rains, as it is only effective when the caterpillars consume it by eating the sprayed leaves of the plant. After 24-48 hours, the caterpillars will stop eating and then die.
Often, a single treatment of B.t. per season is sufficient, but for a large infestation, you may want to spray again after 1 week to make sure your coverage is complete.
Although cabbage worms can be incredibly destructive in the garden, the tips above can help keep the population to a minimum and protect your delicious greens so that you can enjoy them yourself!