Beekeepers and scientists say some store-bought herbs, flowers and seeds may contain a pesticide linked to mass bee die-offs in North America.

Studies have linked neonicotinoid pesticides to an epidemic in the bee-farming community called colony collapse disorder, which is thought to be responsible for the deaths of millions of bees worldwide each year. The Ontario government has taken steps to limit neonicotinoid use in farming, but the pesticides are still used in other provinces and continue to pop up in store-bought plants across the country.

Experts haven't determined the exact harm inflicted by neonicotoids, but bees exposed to the chemical have been known to become lost, confused and inefficient. In many cases, whole bee colonies die as a result of exposure.

Several major retailers have committed to phasing out plants and seeds treated with neonicotinoid pesticides, but the chemicals are in widespread use and phasing them out will be slow. Seeds are often treated with the pesticide en masse, and plants that grow from those seeds are laced with it.

Backyard gardeners are encouraged to ask about neonicotinoids before buying plants at their local greenhouse.

Apiarists have seen a startling rise in bee deaths in recent years, and many blame the growing popularity of neonicotinoids.

Winnipeg-area apiarist Phil Veldhuis cares for about 1,200 hives, and the effects of colony collapse disorder have hit his bees hard.

"Over half of my hives the last two years have collapsed," Veldhuis told CTV Winnipeg last month. He says many apiarists have observed a rise in bee deaths in recent years, coinciding with the growing popularity of neonicotinoid pesticides.

"There's a correlation that we're concerned about," Veldhuis said.

Pesticide companies have blamed the die-offs on changing weather patterns and pests, but studies have shown those to be minor factors in causing colony collapse disorder.

With files from CTV Winnipeg