For the second year in a row, Alberta beekeepers are hearing less buzzing from their hives.

A pest manager with the provincial government says bee populations in over-wintered colonies are down by 25 per cent -- 10 per cent more than normal.

Honey farmer Ernie Martens, who normally runs 1,000 hives in northern Alberta, estimates he's lost 70 per cent of his insects.

"We're trying to figure out ways to rebuild, but I'm not sure how," he said from his farm in La Crete, which is about 800 kilometres north of Edmonton.

Martens said he's been careful to control pests, mites and other stresses on his bees, but suspects he may be facing a mystery ailment that has plagued beekeepers in the United States since 2006.

Beekeepers are finding that adult bees are simply gone, with no evidence of dead bees in the colony. There is currently no known cause for the phenomenon.

Two winters ago, Alberta beekeepers were devastated by an average 30 per cent winterkill rate. An additional 15 per cent of surviving hives were considered weak.

"It was mainly due to mites, and a few other bee diseases," said Paul Laflamme, head of Alberta Agriculture and Food's pest management branch.

But it's not just beekeepers who risk losing their jobs. If heavy losses persist, Alberta's $3.2-billion canola industry would be decimated.