Jonathan Garaas has learned a few things in three seasons of backyard beekeeping: Bees are fascinating. They're complicated. And keeping them alive is not easy.

The Fargo attorney lost hives in his first two years as a novice beekeeper. With nine hives now established near his home and a couple of University of Minnesota bee classes under his belt, he feels like he's got the hang of it, although it's still a challenge.

Every two weeks, he opens the hives to check the bees and search for varroa mites, pests that suck the bees' blood and can transmit disease. If he sees too many of the pinhead sized parasites, he applies a chemical treatment.

Fargo attorney and hobby beekeeper Jonathan Garaas stands next to his hives in July. Dan Gunderson | MPR News

"You can get the book learning. You can see the YouTubes. You can be told by others," he said, but "you have to have hands-on experience. When you start putting it all together, it now starts making sense."

Scientists wish every beginner beekeeper was as diligent.

While experts welcome the rising national interest in beekeeping as a hobby, they warn novices may be inadvertently putting their hives — and hives for miles around — in danger because they aren't keeping the bee mite population in check.

Many hobbyists avoid mite treatments, preferring a natural approach, but that's often a deadly decision for the bees, said University of Minnesota bee expert Marla Spivak.

A varroa mite, seen here infesting the pupae of a developing bee. Judy Griesedieck for MPR News

National surveys by the Bee Informed Partnership show backyard beekeepers in fact are taking the greatest losses nationally," and those losses are often the result of an out-of-control infestation of the varroa mite, said Spivak.

Varroa mites arrived in the United States nearly 30 years ago. But they've become a bigger problem in recent years. Researchers partly blame backyard beekeepers who don't treat their hives.

Untreated hives can spread mites and viruses to other hives within several miles, Spivak said. Healthy bees will invade a dying hive to steal the honey. When they do, they also carry mites with them back to their hives.

"The combination of the mite and the viruses is deadly," said Spivak.

The University of Minnesota Bee Squad, a group that provides beekeeping education and mentoring in the Twin Cities, is seeing more healthy hives rapidly infested with mites and the viruses they carry.

University of Minnesota Bee Squad coordinator Becky Masterman tightens a strap on a bee box on the roof of the Frederick R. Weisman Art Museum at the U. Judy Griesedieck for MPR News

Fall is an especially critical season, said Rebecca Masterman, the Bee Squad's associate program director.

"That late season reinfestation means that your bees are going through winter with a lot of mite pressure and it's really hard for them to come out of that and survive," she said. "It's something that is important enough to really try to get every backyard beekeeper in the country to at least be aware of it."

Masterman said she's also encouraging commercial beekeepers to check their bees more often for surprise mite infestations.

A new online mite monitoring project lets beekeepers anywhere in the country share data on mite infestations and will help researchers track the spread, she added.

Honeybees love to drink the nectar of flowers in urban backyards. Judy Griesedieck for MPR News

A mite control experiment set up this summer should provide more information about the best methods for treating mites in bee colonies.

Bees face other challenges beyond mites, including poor nutrition, disease and pesticides. Even veteran beekeepers say it takes more effort to keep their bees alive.

Beekeepers are independent, so Spivak said she doesn't like to tell them how to care for their bees. But the mite and virus threat to bees, she added, is something that can be controlled.

"I really understand why some people might not like to have to treat their bee colony for mites. It just sounds so awful. It's such a beautiful bee colony and to have to stick some kind of a treatment in there seems so unnatural," she said.

But our bees are dying," she added. "And it's very important to help do whatever we can to keep them alive."