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. 

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

3 comments on “What’s Eating My Barberries?

  1. 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.

  2. 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.

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