Harmful insects

What’s Eating My Barberries?

Barberry geometer caterpillars feasting on barberry leaves. Photo: ask.extension.org

Question: Help! My barberries are being eaten by little caterpillars. I’m sure there must be a thousand of them and they’re chewing all the leaves. What should I do? 


Answer: They’re under attack from the barberry geometer caterpillar or barberry looper (Coryphista meadii), found throughout the United States and southern Canada. It’s a small black caterpillar with a white lateral stripe dotted with orange and an orange head. It’s one of the “inchworms” and moves with a characteristic looping movement. It has a voracious appetite for barberry (Berberis spp.) and mahonia (Mahonia spp.) leaves and dozens are found on each shrub (though definitely not thousands), often defoliating the plant entirely. 

The adult is a rather nondescript brown moth that is active from April to October. There can be several generations per year, although usually only one in the northern part of its range.

BTK insecticide. Photo: Woodstream Brands

Typically, barberry geometer caterpillar attacks suddenly, strips the shrub of most of its leaves within days, then disappears never to be seen again. The plant then puts out new leaves and recovers fully. Given the rapidity with which it strikes, its quick disappearance and its sporadic nature, you may not need to treat it. 

If you want to, try knocking the little guys into a bucket of soapy water or spraying them with BT (Bacillus thuringiensis kurstakii), an organic insecticide sometimes sold as “caterpillar killer.” (That has a nice ring to it, don’t you think?) This product is only effective against caterpillars, so won’t harm other insects, including bees. 

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, laidbackgardener.blog will continue its mission of demystifying gardening and making it more accessible to all.

5 comments on “What’s Eating My Barberries?

  1. Had a problem with my barberry shrubs for years. Leave were virtually gone by August. Bought Bt and faithfully sprayed this year and I have leaves still in September. Hope to break the cycle but will continue to use each year April-October.

    • when did you apply – like what month did you start and how often?

      • Debra Moran

        Started spraying in April and continued through October first year. This second year, I have done the same. Haven’t seen any loopers on bushes yet. Previously, they were visible in early morning in late August. The leaves were virtually gone by end of September. Hoping I will not see any this second year. It works. Sprayed every week and after a rain.

  2. So many insects and diseases are like this, acting up, and then disappearing for years. The coast live oaks are not bothered by much, but then every once in a while, they are harmlessly but shockingly defoliated by their particular caterpillar. The box elders are partially defoliated by their caterpillar right now. The sycamores were mostly defoliated by their anthracnose earlier.

Leave a Reply

Sign up for the Laidback Gardener blog and receive articles in your inbox every morning!

%d bloggers like this: