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Blister beetles

Jeffrey Hahn

blister beetle

Blister beetle
Photo credit: Jeff Hahn

An interesting insect was recently reported attacking the flower blossoms of iris and lupines in large numbers (hundreds) in Wright county. An attractive beetle, they have an iridescent dark green head and wing covers and orange and black legs. They range in size from ½ - 3/4 inches long. This insect is the blister beetle, Lytta sayi (family Meloidae). This insect has no common name.

Like other blister beetles, they have a narrow, elongate body with an ant-like head (wider than the pronotum, the area directly behind the head) and smooth, soft, flexible wing covers. Blister beetles get their name because they contain cantharadin, a substance that can raise blisters when it contacts human skin. Fortunately, the blister beetles you encounter in your garden generally do not have a high enough concentration of cantharadin to be a problem.

Interestingly, the larvae of many blister beetles attack grasshopper eggs. Back in the late 1980's when we endured severe drought, blister beetles became common in response to the high numbers of grasshoppers. Blister beetles belonging to the genus Lytta attack bumble bees and other ground nesting bees.

There are other blister beetles that may be found in gardens, including species that are colored black, gray or are striped. They chew the leaves of a wide variety of plants including peashrub (caragana), alfalfa, and potatoes. If they occur in high numbers, they can cause significant damage to plants. If you need to protect your plants and they are numerous, treat the blister beetles as soon as you notice them. Most garden insecticides are effective including products containing one of the following active ingredients: permethrin, esfenvalerate, bifenthrin, cyfluthrin, carbaryl, or acephate. Be sure the specific product you select is labeled for the plants you wish to treat.

Published in Yard & Garden Line News, Volume 8, Number 9, June 15, 2006

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