Seed World

Going Without Thiram

The Canadian Pest Management Regulatory Agency is calling for a ban of a popular fungicide used in seed treatments for most commercial vegetables grown in Canada. What would the loss of thiram in Canada mean for the United States?

A move by Health Canada’s Pest Management Regulatory Agency to ban the fungicide thiram has raised concerns from both within and outside the country.

The agency is recommending that all uses of thiram — including as a seed treatment — be cancelled in Canada, and it gave industry officials until May 29, 2016, to comment on the proposed re-evaluation. According to Health Canada officials, all comments are currently being reviewed and a final registration decision on thiram is expected by June 2018.

“An evaluation of available scientific information found that, under the current conditions of use, thiram products pose potential risks of concern to human health and the environment,” the PMRA states on its website. “Based on the health and environmental assessments, risks of concern were identified for both workers and the general public in addition to birds, mammals and aquatic organisms.”

The American Seed Trade Association voiced numerous objections to the proposed ban in a letter to the PMRA. “The cancellation of the registration for thiram will have a significant impact on U.S. seed suppliers, Canadian seed dealers and commercial vegetable growers in Canada,” stated Andy LaVigne, ASTA’s president and CEO, in the letter.

According to ASTA, thiram is widely used as a seed treatment on vegetable seed that is treated in the U.S. and then exported to Canada. The association maintains thiram is the preferred choice for seed traders and growers because of its broad functionality, low cost, and the extensive list of countries (including within the European Union) where the fungicide is registered and continues to be sold and used.

ASTA is asking the PMRA to revisit its decision based on new risk data and low potential exposure resulting from the use of thiram as a seed treatment.

“Our analysis of PMRA’s risk assessment uncovered a number of assumptions that are incorrect based on our knowledge of the seed production and seed treatment industries and usage patterns for thiram in Canada,” said LaVigne. “We believe the risk assessment greatly over-estimated the amount of thiram used as seed treatment in Canada and the potential exposure from thiram-treated seed.”

“We believe the risk assessment greatly over-estimated the amount of thiram used as seed treatment in Canada and the potential exposure from thiram-treated seed.” 

— Andy LaVigne

ASTA maintains pulling the popular fungicide from the market will put Canadian farmers at a disadvantage, because seed suppliers would be forced to sell a limited number of varieties that were treated with more expensive fungicides or not treated at all.

“If thiram is not allowed in Canada, seed companies will be required to establish separate inventories of seed to address Canada’s specific restrictions or choose to stop supplying the market. The net result would be fewer options for Canadian growers,” said LaVigne. “Selling untreated seed to Canada would not be a desirable outcome as it would potentially result in more worker and environmental exposure to pesticides,” he added.

Craig Hunter, who oversees crop protection and research for the Ontario Fruit and Vegetable Grower’s Association, says almost all commercial vegetables in Canada are grown with imported seed and most of that is treated with thiram. Banning thiram, therefore, would have far-reaching implications.

Hunter believes the PMRA’s position on the fungicide’s exposure risks is based on outdated data, and that growers should have been consulted prior to the agency’s proposed re-evaluation decision.

Thiram-treated seed has been used for a long time in this country, he says, and taking away this important tool would put vegetable growers in a very tough spot. “How many other fungicides do we have that are registered for use as seed treatment besides thiram?” Hunter asks. “Not very many.”

Hunter maintains planting untreated seed would mean a much greater chance of vegetable crops becoming diseased early and rotting in the ground. That would not only impact farmers’ bottom lines but would also have a serious effect on Canada’s agricultural economy, he adds.