When your cabbages become cue balls and other spring pests

Clockwise from upper right: Cabbage white butterfly, floating row hoop house, cabbage looper moth, cabbage looper caterpillar (top), cabbage white caterpillar (bottom).
Clockwise from upper right: Cabbage white butterfly, floating row hoop house, cabbage looper moth, cabbage looper caterpillar (top), cabbage white caterpillar (bottom).

It happens every year about this time. People point out their excitement about seeing those first butterflies of spring. Maybe it is the brown/orange Red Admiral, or the dappled brown Painted Lady, but usually their exuberance is over the little white butterfly, dancing through the air, right to your vegetable garden.

If you are a vegetable gardener, and specifically a gardener of the “farty family” (cabbage, broccoli, Brussels, cauliflower) as I like to call the cole crops, or Cruciferae family of vegetables, after your first year, you will rue the day you saw those butterflies.

In the garden, you are just ready to harvest that large, beautiful, solid orb of cabbage, but mistakenly decide to wait. Just one more day. What could possibly happen? More than you could imagine. You are mortified to find that large globe has turned into an insect-chewed cue ball of nothingness.

How did this happen? And who is the culprit?

Actually, it is a tag team — the white butterfly (Cabbage white) and the equally damaging, but lesser seen brown Cabbage looper moth. How could these butterflies shred these plants so quickly?

Remember, for farm and garden, it is not the butterfly/moth stage of these insects that cause the problem, it is their teenage life form. You will know what I mean especially if you have ever fed teenage boys. You buy enough groceries for a whole week, and they mow through them in a meal.

It is all about the biology/anatomy and the life cycle. In the adult form, butterflies and moths, the lepidoptera, have siphoning mouth parts that are like a long, neatly coiled garden hoses, called a proboscis. They drink nectar (and in the meantime, get their bodies and wings covered in pollen). No harm, no foul.

The teenager life form, the caterpillar (or larva, or worm, all the same just different names), are voracious eaters of plant material with their chewing mouthparts. Now we have gotten to the heart of the problem.

In the pollinator garden, caterpillars are a welcome sight; never true in the vegetable garden. Whether it is a Ballpark hot dog-sized tomato hornworm, or these tiny, elusive perfectly cabbage-colored caterpillars that decimate the crop seemingly overnight, caterpillars in the vegetable garden are the enemy. (Well except if you have dill, parsley, fennel, or carrots — those caterpillars are for the Eastern Black Swallowtail.)

So, what to do to save your cabbage family crops? The options are fairly simple and quite successful, as long as you outrun the butterflies early, before they can lay their eggs.

There are three forms of control, physical (no, I don’t mean catching the butterfly/moth … although …), biological and chemical.

The physical control is to basically put a security system in place that doesn’t allow the cabbage butterfly/moths to even reach that leafy, egg-laying surface. Floating row cover, or low hoop houses, create a barrier for insect and bird pests.

The cabbage family is an ideal candidate for this type of control, because we do not need pollination for the part we eat. Cabbage, we eat the leaves; Brussels and broccoli, we eat the flower buds, and cauliflower, we eat the interstitial meristem.

Floating row cover used to be hard to find locally, but most big box stores now carry the loose floating row cover, or even easier, the row cover with aluminum hoops already sown into it. And it has a drawstring (like on a hoodie) to keep everything secure. The latter is my personal preference but both work. Floating row cover are also great season extenders, both spring and fall. They allow water and sun to penetrate but keep the varmints at bay.

There aren’t many biological controls out there but one of the greatest is for caterpillars in the vegetable garden and on some ornamentals, IF the caterpillar is truly the teenage version of a butterfly or moth. There are other insects that have larvae that become other types of bugs. This product only works on the caterpillars of lepidoptera — butterflies and moths.

It is a natural occurring bacteria called Bacillus thuringiensis kurstaki more commonly known as Btk and sold under the trade names Dipel and Thuricide. This bacterium only affects caterpillars and without getting too deep in the weeds, gives them a terminal stomach ache.

There is another Bt product, Bacillus thuringiensis israelensis, that controls mosquito larvae. More on that mid-summer.

And then finally, there is the chemical (synthetic) option to control these caterpillars, our old friend, Sevin. Sevin is the brand name of carbaryl. The garden dust or spray used by your grandparents. Still works and is a product that can be used on edible crops. Always make sure you read the label for the days to harvest interval.
This information tells you how many days after application you need to wait to harvest and consume anything treated by the specific chemical you are using.

So, enjoy your early spring butterfly watching, but be prepared.



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