It's being described as the worst winter for beekeepers ever.

Across Ontario, beekeepers are finding millions of their bees dead following the winter with no explanation as to why.

"I started to feel the tops of the hives inside the boxes and they were all chilled and cold, which told me there was no life inside," Andre Pilon describes to CTV News.

The Arnprior beekeeper says across his three local bee yards he cared for 70 colonies, 62 of which have now died.

"If each hive went into the winter with 10, 20, maybe 30,000 bees and all of a sudden there isn't a bee alive in this yard it's pretty discouraging," says Pilon.

The frustrating part is he has no idea why so many of his bees have died.

"We don't know exactly what happened," says Amro Zayed, a biology professor and bee expert at York University.

"Most likely it's probably a combination of things where you have high mite levels, potentially new agro-chemicals, and having this perfect storm of all the stressors."

Zayed adds that the 2021 season was longer than average, which could have allowed a longer period for the harmful Varroa mite to reproduce.

"Thirty per cent mortality would be pretty high, but this year I'm hearing some people with 60, some have 90 per cent mortality," says Zayed of the bee situation across the province. "So it really seems to be an unusually bad year."

Experts say honeybees provide $5.5-billion per year to the agriculture economy in Canada through pollination. With fewer honeybees, there is the potential for shortages in local honey and produce.

"Our honey probably feeds a third of the people in Arnprior who buy honey from our local stores," says Pilon, who adds that his bees probably pollinate the entire town of Arnprior.

"Losing a big chunk of our colonies in the winter will put a big stress on our systems," says Zayed.