DEBLOIS, Maine — The continuing stretch of cold and wet weather has left billions of honeybees trucked into Down East Maine to pollinate the wild blueberry crop hunkered down in their hives for warmth instead of jump-starting the growing season.

Some 14,000 bee hives were recently placed across the thousands of acres of wild blueberry barrens owned in Washington County by Jasper Wyman & Son, the largest of Maine’s commercial growers that collectively tend more than 60,000 acres statewide. Those growers are anxiously awaiting warmer temperatures and sunshine, as the bees they’ve rented won’t forage in rain, winds above 20 miles per hour or temperatures under 53 degrees.

While Maine has more than 50 species of naturally occurring bees known to work the barrens, the level of pollination needed to convert blooms to fruit each spring requires the Down East and midcoast blueberry industry to import billions of bees “from away.” Hives that can contain as many as 60,000 honeybees are trucked in from commercial bee operations located as far away as California, Florida and Texas.

“It’s pretty likely that bees trucked into Maine from the West Coast to pollinate wild blueberries were pollinating California almond groves three months ago,” said Frank Drummond, an entomologist and blueberry pollination expert who teaches within the University of Maine’s Orono-based Graduate Program in Ecology and Environmental Science. “Almond pollination in California requires 1.4 million colonies, and there are only something like 2.6 million colonies in the whole country.”

In recent years, Maine growers have imported about 55,000 hives, each home to a population of 30,000 to 60,000 bees, depending on hive quality. But hive numbers were up significantly last year and could go up again this year. State Apiarist Anthony Jadczak, who serves as Maine’s bee inspector, said the state is on track to exceed 70,000 imported hives this spring, which will provide mid-May to mid-June field housing for as many as 3 billion bees.

At a cost this year of at least $105 per hive, bee hive rental represents a hefty industry-wide expense. At 70,000 hives, that cost could amount to nearly $7.4 million.

“The most expensive production cost for growers is bringing in hives,” Drummond said. “The big growers will get volume discounts and also are willing to pay a 20 percent premium for quality hives with 60,000 bees. The smaller growers might pay $150 for a quality hive or may be willing to pay less for a lesser-quality hive.”

Milbridge-based Wyman’s of Maine is paying about $5 more per hive this spring than it did last year, according to Homer Woodward, the company’s vice president of operations. He’s not surprised.

“The commercial beekeepers are having a hard time keeping things going,” he said.

Since the fall of 2006, commercial beekeepers have been dealing with what’s been termed “colony collapse disorder,” or CCD. For reasons that remain largely unexplained, CCD has been killing off huge percentages of managed bee colonies. Preliminary results of a study recently released by the U.S. Department of Agriculture and industry groups show that 31.1 percent of managed honey bee colonies in the United States were lost during the 2012-13 winter. That represents a 42 percent increase in loss compared to the previous winter. The new loss figures are slightly higher than the six-year average total loss of 30.5 percent.

The USDA last fall convened a three-day “honeybee stakeholders conference” that attracted 175 public- and private-sector experts in the field from as far away as Europe. A USDA analysis of that conference said, in effect, there remain more questions than answers about colony collapse disorder and a “complex set of stresses and pathogens” may be at work, including parasitic mites, multiple viruses and bacterial diseases and pesticide exposure.

Despite what the USDA describes as a “remarkably intensive level of research efforts,” the report notes that “overall losses continue to be high and pose a serious threat to meeting the pollination service demands for several commercial crops.”

According to the American Beekeeping Federation, an estimated one-third of all food and beverages are made possible because of pollination, mainly by honey bees. In the United States, pollination contributes to crop production worth $20-$30 billion in agricultural production annually, the group said.

In Maine, Jadczak said, such crops extend beyond the blueberry barrens to cranberry bogs, apple orchards and areas of Aroostook County that support canola and squash crops. After making their rounds in Maine, he said, these managed hives will be trucked to Wisconsin, Massachusetts and New Jersey to work those states’ cranberry crops.

Jadczak said he does spot checks on commercial hives, looking for bacterial diseases and parasitic Varroa mites that not only feed on honey bees but can infect bees with viral diseases, much like mosquitoes spread malaria.

“Things are coming in pretty clean,” he said. “They all come into Maine with certificates of health issued at their points of origin. And it’s in the best interest of the commercial beekeepers to make sure they are healthy.”

Drummond was recently awarded a $3.5 million federal grant to study Maine’s native bee population at 16 blueberry growing operations in Washington and Hancock counties. His research supports a field management strategy that utilizes four hives per acre to maximize fruit production. Field studies done in Washington County and elsewhere in Maine have shown that blueberry yields can be increased by as much as 1,000 pounds an acre for each hive servicing that acre, up to five hives per acre. Those results presume good weather, adequate soil moisture and good fertilization and pest management.

Yields can range from under 1,000 pounds per acre to more than 15,000 pounds per acre, depending on a number of variables, including pollination, fruit set, weather and pests. Some Down East barrens consistently yield 10,000 pounds per acre.

Drummond said some growers find four hives per acre cost-prohibitive, while others will introduce as many as 10 hives per acre to ensure good pollination despite Down East Maine’s changeable spring weather.

“You might bring in four hives and then have a week or more of cold and wet weather, like we’re seeing now, when the bees won’t forage and will stay in their hives to stay warm,” Drummond said last week. “When there finally is ideal weather — with sun, temperatures above 50 and winds under 20 miles per hour — if you have eight hives working, instead of four, it can make up for the time lost to bad weather. It’s a matter of capitalization and risk aversion.”

Maine’s 2012 wild blueberry crop was a good one, according to the USDA’s post-harvest calculations. The department’s National Agricultural Statistic Service put the total yield at 91.1 million pounds, well above Maine’s five-year average of 84 million pounds. The 2011 yield weighed in at 79.9 million pounds. Valued at 76 cents per pound, the 2012 crop was worth $69.1 million.

David Yarborough, the University of Maine Cooperative Extension Service’s wild blueberry specialist, said growers are coming off a winter that provided plenty of snow cover and relatively mild temperatures, both limiting winter kill.

“The bloom looks good, but we’re only 5 to 10 percent into it,” Yarborough said. “We’ll know more next week and the week after that.”

Woodward said he likes what he’s seen in Wyman & Son fields, some of which have been cleared of large rocks since last year’s harvest to allow more mechanical harvesting this year.

“The cool spring will likely postpone the bloom, but the blossoms will get by the frost,” he said. “We had frost here as late as last week.”

Although Maine has 60,000 acres of blueberry barrens, only half of those acres are in production each year, given a two-year cultivation cycle. Jasper Wyman & Son is the largest of the six companies in Maine that process, freeze and package wild blueberries. There’s also one fresh-pack cooperative in Maine. An estimated 99 percent of all the berries harvested in Maine are frozen for use as food ingredients.