The season of blister beetles has arrived.
As hungry blister beetles move into gardens and hay fields, growers are faced with the usual conflicts on decisions about controlling them.
"The ash-gray and striped blister beetles, in particular, are notorious for quickly stripping the foliage from vegetable plants – tomatoes, beans, peas, potatoes. Blister beetles also attack such field crops as alfalfa and soybeans, which generally is what puts livestock at risk. Hay that contains blister beetle body parts can put cattle off their feed and kill horses," said Ward Upham, horticulturist with K-State Research and Extension.
The "organic" way to control blister beetles in the garden is to hand pick and squash the insects. The only safe way to do that, however, is to wear closed shoes and protective gloves, Upham warned.
Blister beetles contain a fluid called cantharidin, he explained. It's an irritant for both external and internal animal tissues. The typical result on human skin is large, watery, erect blisters.
Kansas is home to numerous blister beetle species that can vary in size, color and color pattern. But, most are rather drab and measure between one-half and three-quarters of an inch long. They also share a general shape: a long, narrow, soft body with a large-seeming head, wing covers, and what looks like an unusually long and skinny neck (actually its thorax).
Deciding how and whether to control the pests can be difficult, Upham said, even though chemical controls also are available.
"Experienced gardeners know the beetles tend to gather in big crowds. They're also aware the pests may move on in a day or two," he said. "Farmers, on the other hand, know the last thing they need is dead blister beetles in a crop being grown for hay."
The chemicals approved for controlling blister beetles in gardens include cyfluthrin (PowerForce Multi-Insect Killer) and gamma- or lambda-cyhalothrin (Spectracide Triazicide, Bonide Beetle Killer). Cyfluthrin requires no waiting period between application and tomato harvest. Lambda- and gamma-cyhalothrin have a five-day waiting period on tomatoes and peppers.