Natural Controls For Cabbage Whites

Fun craft project with kiddos

Of Kale And Cabbage Butterflies

Cabbage Whites, Cabbage Moths, Cabbageworm, all are names for the very common (yet introduced) Cabbage White Butterfly (Pieris rapae). Under two inches wide, white or cream with distinctive black dots on their wings, Cabbage Whites thrive in my garden, fluttering amongst the flowers and swooping down to-uh oh, lay eggs on my kale, broccoli, and cauliflower. Since I grow many kinds of kale and other brassicas, any damage is spread between many plants. I never worry much about a few nibbled leaves and it doesn’t really bother me to discover a clutch of eggs on the underside of foliage. Extra protein, right? The caterpillars are not so easy to overlook, but it’s simple enough to pick them off. You definitely do want to pick them off your broccoli and cauliflower because the larvae poop stains cauliflower curds and broccoli buds, which is not appetizing.

This is a very dry year and a lot of little critters are finding good pickings in well watered gardens like mine. While I’m happy to host a constant haze of pollinators, I’m not so pleased that a LOT of Cabbage Whites are calling my garden home. Yes, they’re pretty and kinda charming as they swirl in their spiraling mating dances, but it’s getting to be a bit much. What to do? I recently heard about making Cabbage White decoys from paper or white plastic; they’re supposed to coax incoming females to move on, since the girls are thought to prefer less crowded places. After doing some research, I spent a happy afternoon making dozens of decoys and later got enthusiastic help from my grandkids as well. If you want to try your hand, here’s a good explanation:

http://goodseedco.net/blog/posts/cabbage-butterfly-decoy

Inserting cloth covered floral wires makes the butterflies flutter

However

As I did a little MORE research, I found a counter argument from a very reputable source debunking the idea that Cabbage Whites are actually territorial and challenging the usefulness of the decoys. Here’s the debunk:

MothBusters: Testing a Common Myth About a Small Butterfly

But Wait, There’s More!

The debunking experiment was limited and the professors admitted that there were too many variables to be sure that their findings were accurate or widely applicable. Meanwhile, there are zillions of posts from gardeners who swear by the decoys as well as quite a few from folks who don’t find them effective. I’m considering the issue to be unresolved and worthy of further investigation; after making all those decoys, I’m really curious to see what the effect, if any, looks like in my gardens. I have several plots about a quarter of a mile apart so I’m putting decoys in all of them and spending a little time each day observing butterfly behavior.

What To Watch For

Imported (probably accidentally) from England and Europe, the Cabbage White is by now a very common garden pest throughout North America. If you don’t want to give the decoys a try, Cabbage Whites are easiest to eliminate in the caterpillar stage by spraying foliage with organic controls like Bt (Bacillus thuringiensis) or Neem oil. Applying either substance once a week for 5-6 weeks will wipe out successive waves of emerging larvae, little green caterpillars that love to nestle in the heart of a head of cauliflower or broccoli. Neem works initially by smothering the eggs, little cream colored, barrel-shaped blobs laid in neat rows. It also smothers the caterpillars, while Bt works when the caterpillars eat foliage that’s been sprayed. Since these treatments also kill off other insects, including caterpillars on the way to becoming different butterflies, it’s best to apply them only to affected plants and only when there’s enough damage to warrant intervention.

In gardens where they find a happy home, Cabbage Whites overwinter as pupae, which look like lumpy, folded green leaves, usually attached to a stalk of kale or broccoli. By April, the butterflies emerge and start laying eggs, which hatch into larvae (caterpillars) in about a week. The caterpillars fatten up for another couple of weeks, then pupate on a host plant. The full cycle from egg to adult takes between 3 and 6 weeks, and there can be as many as five generations each year. By monitoring foliage weekly, checking leaf fronts for holes and backs for eggs, you can tell pretty quickly whether your garden will be lightly or severely infested. Commercial growers start to worry if they find 2 out of ten leaves affected, but they have to worry about half a dozen pests that can affect the appearance of their crop.

Or Let Them Be

Home gardeners may not feel that any intervention is needed except in unusual years when challenging conditions make for extra problems. If you are growing cabbage and don’t like finding cabbage “worms’ burrowing into the heads, try growing cooler season varieties that head up in early spring, before the first Cabbage White butterflies emerge. Cabbage varieties with the greatest resistance to Cabbage Whites include Chieftain Savoy, Mammoth Red Rock, and my favorite, super crinkly Savoy Perfection Drumhead.

Summery Cabbage Salad

I love fresh cabbage in salads but am not wild about the heavy, oily dressings usually used. This is a current favorite recipe combining cabbage and kale with cherry tomatoes, fresh basil, and a little mint. If you don’t like the flavor and crunch of raw cabbage as much as I do, give the raw greens a splash of vinegar and let them stand for 10 minutes before adding other ingredients; the vinegar will lightly “cook” the greens, making the texture softer and the flavor milder. Rice vinegar is especially gentle, while cider vinegar adds a more pungent brightness.

Crunchy Cabbage Salad

2 cups shredded green cabbage
2 cups kale cut in ribbons
Kernels trimmed from 1 ear sweet corn
1 cup halved cherry tomatoes (mixed kinds)
1/4 cup green onions, thinly sliced
1 quarter cup stemmed basil, chopped
1-2 tablespoons chopped mint (to taste)
1-2 tablespoons rice or cider vinegar
pinch of kosher or sea salt
few grinds black pepper

Combine all ingredients and gently toss. For a more mellow, less crunchy salad, let stand 5-10 minutes before serving. Serves 4.