Research that demonstrates how greenhouse pollinating bees transmit disease to wild bumblebees shows growers need to seal up escape routes.
Michael Otterstatter, research scientist at the University of Toronto, studied bees in and around large greenhouse operations in southern Ontario.
He found high disease levels in commercially bred bees used for pollinating vegetables and in wild bees hovering in nearby fields.
“It was shocking to see how much they were carrying,” he said, citing the presence of the parasite Crithidia bombi.
The parasite weakens and often kills bees, with mortality rates rising by 50 percent in wild bees. Otterstatter said the commercial bees escape through automatic vents in greenhouses that open and close during the day.
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They contaminate outside flowers with disease, which wild bees then pick up when they visit the same plants.
High mortality rates in wild bee populations reduce the effectiveness of queen bees in establishing new nests in the spring and reduce the number of active worker bees critical to gathering pollen.
Otterstatter said greenhouse growers need to implement measures to keep bees inside their buildings.
“If contained, disease goes away very quickly,” he said.
