Preliminary results from an annual survey of beekeepers suggests that 31 percent of the nation's bee colonies died over the winter, raising new concerns over whether the country has enough honeybees to pollinate America's food supply.

Details provided to Secrets from the industry journal Bee Culture and the Bee Informed Partnership, which includes the Department of Agriculture, showed that hive deaths increased 42 percent from the year before.

The preliminary report, however, did not give any reason for the jump in dead honeybee hives, though industry representatives told Secrets that the main culprits are likely the pests like the Varroa mite, harsh weather and the mysterious Colony Collapse Disorder.

"It's up from last year's mild winter, which should tell you something," said Kim Flottum, editor of Bee Culture.

The national bee hive analysis comes on the heels of a federal report raising grave concerns that there are not enough bees to pollinate the nation's crops. With 31 percent less hives, those concerns will grow. The nation went into the winter with 2.62 million hives, about a third of what the U.S. had in 1947.

Some 6,287 beekeepers who manage about 600,000 hives responded to the survey. Most were hobby beekeepers; many industrial beekeepers who truck hives into orchards, fields and nut groves said they were too busy to respond and several of them have reported much higher losses.

The report said that survey participants considered a loss rate of 15 percent as "acceptable," but 70 percent of them suffered losses greater than that.