Canadian beekeepers are suing the makers of popular crop pesticides for more than $400 million in damages, alleging that their use is causing the deaths of bee colonies.

The proposed class action lawsuit was filed Tuesday in the Ontario Superior Court on behalf of all Canadian beekeepers by Sun Parlor Honey Ltd. and Munro Honey, two of Ontario's largest honey producers, the Ontario Beekeepers Association announced Wednesday.

"The goal is to stop the use of the neonicotinoids to stop the harm to the bees and the beekeepers," said Paula Lombardi, a lawyer with London, Ont.-based law firm Siskinds LLP, which is handling the case.

As of Thursday morning, more than 30 beekeepers had signed on to participate in the class action.

The lawsuit alleges that Bayer Cropscience Inc. and Syngenta Canada Inc. and their parent companies were negligent in their design, manufacture, sale and distribution of neonicotinoid pesticides, specifically those containing imidacloprid, clothianidin and thiomethoxam.

The pesticides, which are a neurotoxin to insects, are widely coated on corn, soybean and canola seeds in Canada to protect the plants from pests such as aphids. Studies have shown that bees exposed to the pesticides have smaller colonies, fail to return to their hives, and may have trouble navigating. The pesticides were also found in 70 per cent of dead bees tested by Health Canada in 2013.

The European Commission restricted the use of the pesticides for two years and Ontario has indicated it will move toward regulating them, due to concerns over bee health.

Bayer maintains that the risk to bees from the pesticide is low, and it has recommended ways that farmers can minimize bees' exposure to the pesticide.

Both Bayer and Syngenta told CBC News they wouldn't comment on the lawsuit because they haven't yet been served with it.

The lawsuit is seeking more than $400 million in damages, alleging that as a result of neonicotinoid use:

The beekeepers' colonies and breeding stock were damaged or died.

Their beeswax, honeycombs and hives were contaminated.

Their honey production decreased.

They lost profits and incurred unrecoverable costs, such as increased labour and supply costs.

Beekeepers or companies involved in beekeeping services such as honey production, queen bee rearing and pollination who are affected and want to join the lawsuit are asked to contact Lombardi.

The Ontario Beekeepers Association is not directly involved in the lawsuit, but along with the Sierra Club Canada Foundation, helped connect beekeepers with the law firm. The association also helped with the research for the lawsuit.