In a spring ritual as old as life itself, Steve Ellis' bees return to their hives day after day loaded with pollen from the dandelions and flowering trees that are in full bloom across central Minnesota.

But for too many of them, a day of foraging ends in convulsions and death.

"You wouldn't think people could get attached to insects," said Ellis, a commercial honey producer from Barrett, Minn. "But it's hard for us to see our bees getting injured like that."

Hard enough that Ellis and other beekeepers from Minnesota and across the country this month asked the federal government for a temporary ban on one the most widely used pesticides until its effect on bees is clear. They fear it is contributing to a worldwide die-off and the inexplicable phenomenon known as "colony collapse disorder" that is devastating honeybee hives.

"We are asking the EPA to do its job," said Jeff Anderson, a commercial beekeeper from Eagle Bend, Minn. "Give us products that are safe."

The beekeepers and several environmental groups argue in an emergency petition filed with the EPA that the agency failed to require some legally mandated field testing before the pesticide was approved in 2003. New research, including two studies published last week in the journal Science, raises serious questions about its effect on pollinators of all kinds, they maintain.

The EPA said it has based its continued approval on hundreds of studies. In 2010, the agency said no data shows that bee colonies are harmed by exposure. Nevertheless, it agreed to accelerate its routine review of the pesticide -- meaning it will be completed in 2018.

Meanwhile, officials with the manufacturer, Bayer CropScience, say they are confident that the research will continue to prove the product is safe for bees when used appropriately.

"I tend to believe that science will win out over emotion," said Jack Boyne, director of communications for Bayer CropScience.

The beekeepers and others say they filed the emergency petition because they fear that the EPA's review process will deliver a verdict too late for the nation's honeybees and the farmers who rely on them.

"Seventy percent of crops -- apples, oranges, zucchini, melons, strawberries -- they all need pollinators," said Vera Krischik, an associate professor of entomology at the University of Minnesota who studies the pesticides and bees. "It's a huge issue."

Then there are the unknown numbers of bumblebees, wasps, butterflies and other wild pollinating insects that fill the same role across the natural world.

"We are headed in a very dangerous direction," Ellis said.

Anderson said beekeepers have always been on the front lines of the nation's pesticide wars; that's how he got into business in the first place. His wife's grandfather moved his California beekeeping business to Minnesota in the early 1960s after another pesticide, Sevin, critically damaged his agricultural pollinating business.

Anderson went on to win a landmark case at the Minnesota Supreme Court against the state Department of Natural Resources over pesticide drift that killed his bees.

Like Ellis, he is among the gypsy beekeepers who follow the seasons, pollinating almonds, cherries and other crops in the South and West in winter and returning to Minnesota in the spring to make honey.

New breed of pesticides

The pesticides beekeepers are fighting now are different than those of the past, Anderson said. Those were applied at predictable times, making it easy to keep bees out of harm's way.

The pesticides most widely used now are among a class of nicotine-based chemicals called neonicotinoids that are designed to become an intrinsic part of the plant. They were developed in large part because they are much less toxic to humans and other mammals than previous pesticides. But in high doses, they are a neurotoxin to insects.

Since their introduction in the 1990s, they have exploded in popularity among farmers and in products for home gardeners. Today, 90 percent of seed corn is coated with the pesticides before planting, and the chemicals are the active ingredient in hundreds of back-yard products.

The pesticide is sprayed on plants and, when used as a seed coating, it grows into all parts of the plant, including the pollen and the nectar that bees eat.

When used properly, say both Bayer and the EPA, the toxin levels are not high enough to hurt bees. But many scientists and beekeepers say that, as in all pesticide regulation, the field research is questionable because it's done by the manufacturer.

The emergency petition, filed by 30 beekeepers and national environmental groups that includes Beyond Pesticides and the Center for Food Safety, targets just one of the six neonicotinoids, clothianidin, in part because they say the field study for that one was inadequate. Officials from Bayer and the EPA disagree.