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BLISTER BEETLES

Bad to touch and for your flowers!

By: Sandy Feather 2011
Penn State Extension


Q. Something has completely stripped the foliage from my anemones (Anemone x hybrida). All that is left is flower stalks and flower buds. I live with a sizable deer population and do not think they are to blame this damage is different. I managed to catch one of the insects I think is responsible. Can you identify it and tell me how to control it in the future?

A. The insect enclosed with this question was a black blister beetle (Epicauta pennsylvanica). Blister beetles often feed in groups (gregariously) and are quite capable of stripping foliage from many species of plants, including ornamentals and vegetables. They seem to arrive like a biblical plague, then disappear. They are considered important pests of alfalfa, especially in western states where their populations are greater due to drier conditions and higher grasshopper populations.

Although their feeding does not result in economic damage to the crop, dead beetles crushed into bales of hay present a toxicity hazard to livestock eating that hay. Horses, cattle, sheep and poultry can be poisoned if they consume too many dead blister beetles in baled hay. Horses are especially sensitive.


MORE BLISTER BEETLES

Other species of blister beetle can also be found in Pennsylvania, including striped (E. vittata), ashgray ) Epicauta fabricii) and margined (E. pestifera). They are called blister beetles because they contain cantharidin, a defense chemical that protects them from predators. If you accidentally crush one, it can cause painful blisters on your skin. That is the same substance that is so toxic to livestock.

 

Adults have long three-quarter to one inch narrow bodies.  The sharp division between head and thorax makes blister beetles appear to have necks, unlike most insects. The head and thorax are ant-like, and they have long antennae that are about one-third the length of their bodies. They feed on pollen and nectar as well as foliage and are very attracted to flowers. Your anemone flowers must have survived because they were not open yet.
 


LIFE CYCLE OF BEETLES

Adult females lay cluster of eggs in the soil in late summer, especially near grasshopper eggs pods. Once the blister beetle eggs hatch, the small larvae search actively for grasshopper egg pods. Once a larva finds one, they feed and molt at short intervals, eventually losing the legs that made them so mobile at first. They pupate in the soil and hatch as adults in mid-late summer, depending on the species and weather conditions.

While blister beetles are not the problem for home gardeners that they are for farmers and horse owners, such localized outbreaks can occur occasionally. Chance are, most gardeners will not even notice them until the damage is severe, and then it is too late to do anything about it. The blister beetles will have moved on, and you may never see the culprit that damaged your plants. Preventative sprays are not recommended, even in alfalfa fields. If you find them, put on gloves and carefully knock them into a jar of soapy water. Do not handle them with your bare hands, even after they are dead, to avoid painful blisters.
 

 

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