Alfalfa growers don't often see the need to treat blister beetles in alfalfa, says Glenn Studebaker, University of Arkansas extension entomologist.

It's not economically feasible when they can sell untreated hay to customers who don't fear the beetles' toxin.

But Arkansas horse owners, and the people who sell hay to them, have to find hay grown farther from home each year, says Phil Mayer. Mayer sells horse hay in Clarksville, AR. He's had to travel as far as South Dakota for hay that doesn't contain the pest so deadly to horses.

Arkansas isn't known for its alfalfa hay. And what's grown there usually contains blister beetles. So Mayer used to buy hay in Oklahoma. No more.

“Oklahoma is full of blister beetles,” says Mayer. “Now Kansas is getting them too, so I'm going farther up. I think growers think it's the other guy's problem. When it hits home, that's when they'll wake up.”

In Arkansas, blister beetles have been known to defoliate whole fields. That's the only time growers find that spraying pays, says Studebaker.

All horse owners and alfalfa growers should be concerned about blister beetles, says Phil Mulder, Oklahoma State University extension entomologist.

“Just about every state (see map) has problems with blister beetles at some time or another,” says Mulder. “No one is immune to the problem.”

He suggests six ways buyers and growers can avoid the pest:

  1. When buying hay for horses, find out when it was cut.

    “Purchasing first or last cutting hay, at least here in Oklahoma, is relatively safe. We have never spotted the blister beetle in Oklahoma before late April or even early May. And most of our first cutting is done in April,” he says.

    Final cuttings are made in early October, after adult beetles die.

  2. Reduce weed problems. The fewer flowers to attract beetles, the fewer beetles there will be, he says.

  3. Cut at bud stage rather than first bloom, again to keep from attracting beetles.

  4. Cut alfalfa with a sicklebar and don't condition it. Driving on windrows can kill blister beetles, too, and the toxin will end up in bales. Live beetles migrate out of cut hay.

  5. Watch grasshopper populations. Immature blister beetles feed on grasshopper eggs, so large numbers of grasshoppers could be followed by blister beetles.

  6. Growers and buyers should work together to reduce blister beetle risks.

“If you hope to buy blister beetle-free hay, then you better come across with some help to guarantee that the hay is blister beetle-free,” says Mulder. “Say you want to purchase some summer cuttings that might be higher in protein, but you don't want to run the risk of blister beetles. Then pay for the treatment. Or meet the grower halfway. Or give him a premium when he sells that hay to you.”