The butterfly who gives caterpillars a bad name

Today’s Backyard Nature: the Butterfly who gives caterpillars a bad name.
This is a Cabbage White, a species from Europe who aims for leaves in the Cabbage / Mustard family.
In this blurry pic, she is laying an egg on annual Honesty, an exotic mustard.
See her abdomen curving up to place an egg under the leaf?
The hatchling will be one of the dreaded, green caterpillars called “cabbage worms.”

When I talk to people about “caterpillar host plants,” and then these people say they HATE caterpillars, THIS particular caterpillar is usually why. 

Many gardeners who grow kale, cabbage, arugula, brussels, etc. learn to hate these caterpillars. And by association, learn to hate all caterpillars.
And then, to reach for the pesticide.

Some of these gardeners might not realize that all butterflies begin life as caterpillars, and that if we want more butterflies, we need more caterpillars.

However, we don’t need more of these.
In Nashville — like the rest of North America — Cabbage Whites are an exotic species, and one of “the world’s most invasive pests affecting agricultural crops.”

What I didn’t realize till now, is that I’ve been making Cabbage Whites at home. Not on purpose, but accidentally, when I’ve let an accidental flower thrive.

Honesty / Money Plant is not native here, and spreads like mad. I left it alone the first few years, because “Oh, what pretty flowers!”
But soon, the pretty flowers became thugs. After I filled the wheelbarrow four times in one hour, I vowed to cull them before they developed seedpods.
(The seedpods look like “coins,” thus: Money Plant.)

But after seeing today’s Cabbage White start a new generation of “cabbage worms,” I have a reason to cull even sooner. Each adult female can lay 300-400 eggs.
I don’t want to make new butterflies that make my kale-growing neighbors hate all caterpillars.

Still, it feels wrong to destroy a plant in flower, so I’m compromising. I’m setting cut stems in buckets and jars outside. Pollinators can partake of nectar and pollen, and passersby can see bouquets on the porch. When the flowers finish, I’ll throw them on the compost.
Seeds won’t get a chance to grow, and neither will the caterpillars.

– – –

But what if we grow kale? Do we have to sacrifice our crops?

My experienced organic gardener / Tennessee Naturalist buddy says that timing is everything. If we work with the local Cabbage White life-cycle, we can have our kale and eat it, too.

This works for her:
“As soon as I see any Cabbage White butterflies or caterpillars in the spring, I try to harvest all of my kale.
… I start kale plants from seed in August. Starting them in late summer gives them a chance to grow well throughout the fall. The Cabbage White population has died down by then so it doesn’t cause me any trouble. We harvest kale all fall, winter and early spring.”
“I don’t try to grow kale during the summer. It’s just too discouraging.”

– – –

LOOKALIKES!

Nashville has other white and pale yellow butterflies, so let’s not assume all whitish butterflies are “bad.”
Rita Venable’s Butterflies of Tennessee: Field & Garden is a must-have book for even casual butterfly / caterpillar observers.

– – –

HOST-PLANT EDUCATION:

Cabbage Whites can be a great starting point for “What does Host Plant Mean?”
Butterflies need two kinds of plants: nectar plants for adults, and “caterpillar host plants” for caterpillars.
Host plants are what a female butterfly aims for when time to lay eggs, and what the hatchlings eat until time to pupate. Evolution has given us butterflies who require very specific host plants. Cabbage Whites must have cabbage-family plants in order to make more Cabbage Whites.
The same is true for our native butterflies. The most famous example is the Monarch, who must have Milkweed leaves.
Other local examples: Zebra Swallowtails must have Pawpaw leaves;
Spicebush Swallowtails must have Spicebush / Sassafras leaves;
Black Swallowtails must have the carrot family;
Gulf Fritillaries must have our State Wildflower, the Purple Passionvine (or the Yellow, also native); and so on.

If we want more butterflies, we need to grow plants that “host” new caterpillars. (And skip all pesticides, including mosquito yard sprays.)

– – –

LINKS:

Cabbage White / Pieris rapae photos and info at the Univ. of Florida (link).
Note yellow racing stripes on caterpillars. Note natural predators and a some info about what the caterpillars do and do not prefer (darker greens and reddish leaves are less likely to get eaten).

Honesty  / Money Plant / Lunaria annua info at Missouri Botanical Garden (link.) Note “Where is this species invasive in the U.S.”, which leads to EDDMapS, which includes Davidson County.)

---

more
SidewalkNature:

Follow me on Instagram, where my posts are 100% nature, and most of it the Sidewalk kind.

Subscribe to Sidewalk Nature and get an email when I update. I never share your info.

SUBSCRIBE

I’m not fond of facebook, but some people aren’t on Instagram, so I post nature things there from time to time.

Comment on this post, or if you have a general comment or question, click the Contact page.
Corrections, suggestions, and new friends are always welcome.

---

Bio:
Joanna Brichetto is a naturalist and writer in Nashville, the Hackberry-tree capital of the world.
She writes about everyday marvels amid everyday habitat loss at SidewalkNature.com and on Instagram (@Jo_Brichetto); and her essays have appeared in Creative Nonfiction, Brevity, Fourth Genre, Hippocampus, The Hopper, Flyway, The Common, City Creatures, The Fourth River, and other journals. An almanac of urban nature encounters is forthcoming.