In the first test of a landmark environmental law, Minnesota has compensated two beekeepers whose hives were severely damaged last spring by toxic dust that drifted off the fields of a neighbor planting corn.

Investigators from the state Department of Agriculture confirmed, in effect, what beekeepers have been saying for years: Even when used according to law, the most widely used class of insecticides in the world are acutely toxic to honeybees under routine circumstances.

Even more importantly, said state Sen. Rick Hansen, the finding marks a precedent in the ongoing national fight over the controversial group of insecticides called neonicotinoids, which have been implicated in the decline of bees and other wild pollinating insects.

“This is the first action of any state, a finding of fact, that neonicotinoids are harmful to bees,” said Hansen, who sponsored the 2014 law that created the compensation system. “Once you have a state compensating people for a loss, it’s real.”

An official with Bayer CropScience, which makes the insecticide, said he is not familiar with the case and could not comment.

The insecticide in question, clothianidin, is used as a coating on most of the corn and soybean seeds used in American agriculture. Farmers use it as a preventive to protect seedlings from insects in the soil. As the plant grows, the toxin grows with it, making the entire plant poisonous.

How poisonous — and how much poison leaches into the environment season after season — has been the subject of intense debate. The state Department of Agriculture is conducting a review of neonicotinoids in Minnesota, with results expected in coming months.

The U.S. Environmental Protection Agency is also reviewing compounds, and recently announced that one of them, imidacloprid, showed clear damage to hives and honey production even when used appropriately on some crops. Its review of clothianidin is expected to be complete by the end of this year.

Bayer CropScience has disputed the EPA’s finding on clothianidin, as well as multiple other international studies showing that the insecticides, a neurotoxin for insects, have sublethal effects on bees’ ability to navigate long distances, communicate inside the hive and reproduce.

But Bayer has acknowledged that drift from corn planting, which can contain extremely high levels of the toxin, can damage bees and other insects. The company says such events are rare, but has supported the development of other products to help solve the problem.

Beekeepers, especially those in the Midwest, say that drift from corn planting is a common and serious problem that occurs just when their bees need to be out collecting nectar for the honey crop in springtime.

“We are still having issues with corn planting and treated seeds,” said Gary Reuter, a researcher with the University of Minnesota’s bee laboratory, who works with beekeepers around the state.

‘This is where I live’

Some commercial beekeepers, who travel with their hives to provide pollination services across the country, wait until after corn planting is done before returning to Minnesota. But the two beekeepers who received compensation for losses say they don’t have that option.

“This is my life, this is where I live,” said Pam Arnold, who manages five hives on her organic farm near Scandia.

Her “postage stamp” farm is next to a wildlife area, a city park and the St. Croix River. “You’d think of all places on earth, we would be in the best setting to protect bees,” she said.

But last spring her neighbor across the road planted corn that was later found to have the standard insecticide coating. On that day, the wind was blowing toward her hives, and those of Kristy Allen, another beekeeper who shares Arnold’s bee yard.

Allen immediately suspected what had happened. Tests performed as part of the Agriculture Department’s investigation found that even two days after the incident, the dead bees carried acute levels of the toxin, and tests of nearby dandelions showed significantly higher concentrations, according to the state’s report.

Allen, founder of the Beez Kneez, a Minneapolis honey company, fought for the compensation law and testified before the Legislature. Now, she said, being one of the first beekeepers to collect damages from it “is an irony that kills me.”

There was no violation of state or federal law governing pesticide application, agriculture officials said. Seed coatings are not considered a pesticide application like spraying, because farmers buy the seed ready to plant. The application occurs at the seed distribution and processing plant, they said.

But that, said Allen, signals a significant failure in pesticide law.

“The fact that MDA is compensating me for something that is not illegal is crazy to me,” she said. “It means something is broken.”

Hard to prove

Since 2014, the Agriculture Department has investigated 10 complaints from beekeepers, mostly small operators, but found evidence of a pesticide kill only in the one in Arnold’s yard. It shows how difficult it is to prove pesticide kills, said John Peckham, program supervisor at the state agriculture department.

“These are the most complex cases we ever deal with,” he said.

But few beekeepers use the compensation program, especially commercial beekeepers, said Dan Whitney, head of the Minnesota Honey Producers. Compensation is capped at $20,000, or $230 per hive, which doesn’t cover the kinds of losses they experience, he said.

Moreover, a 2015 change in the law requires beekeepers to register the location of their hives with an online site so pesticide applicators can see where they are and contact the beekeeper.

“You have to move your bees or go out there and cover them with nets” so they don’t fly, he said, which is impractical for large operators. Besides, corn and soybean fields cover close to half the state, so there are not many safe places to go, he said.

“We are in a tough spot,” Whitney said.

Josephine Marcotty • 612-673-7394