An encounter with black blister beetles

Black blister beetles enjoy making meals of maple-shaped leaves and cause problems when they infest hay.

Courtesy of Donna Williamson
Black blister beetles munch on Japanese anemone leaves.

I ran into some black blister beetles this week. I haven’t seen any in about 15 years, but once you have encountered these critters, you don’t forget them.

They travel in groups and love plants with maple-type leaves, such as on clematis, Japanese anemone, and grapes.

I think people must have wide-ranging genetic knowledge because when you look at black blister beetles, you instinctively know not to touch them.

I understand they also can infest alfalfa hay to the detriment of horses that suffer when they eat the insect or plants the insect has been crushed upon.

The beetles contain the chemical cantharidin, which can poison horses and cause blisters on human skin.

A friend told me that when you see a group of the beetles coming, you could “sweep” them along and past your garden. I'm not sure I want to annoy them to that degree.

The good part is that they eat grasshopper eggs as part of their development. And that 15 years may go by between encounters!

Do black blister beetles appear in your area? And do they move along quickly?


Donna Williamson blogs regularly at Diggin' It. She's a master gardener, garden designer, and garden coach. She has taught gardening and design classes at the State Arboretum of Virginia, Oatlands in Leesburg, and Shenandoah University. She’s also the founder and editor of Grandiflora Mid-Atlantic Gardening magazine, and the author of “The Virginia Gardener’s Companion: An Insider’s Guide to Low Maintenance Gardening in Virginia.” She lives in the Shenandoah Valley of Virginia. To read more by Donna here at Diggin' It, click here.

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