Currently under review in Canada, mancozeb is a potato industry staple for fighting late blight and early blight. Its proponents fear its loss would spell higher production costs for farmers and would remove a vital tool for managing disease resistance in potatoes.
Canadian potato farmers could be facing higher production costs with the potential loss of a key weapon against late blight.
Mancozeb is a relatively inexpensive, Group M fungicide that’s used extensively in Canada to combat late blight and early blight, with some growers applying the chemical up to 10 times per season on their potato fields.
The broad-spectrum fungicide is currently under review by Health Canada’s Pest Management Regulatory Agency due to concerns related to human health and environmental safety.
In June 2018, the PMRA completed a re-evaluation of mancozeb and ruled it unacceptable for agricultural use —with the exception of foliar applications in potato. Only a few months later, however, the agency changed its stance and proposed that all uses of mancozeb be cancelled, except for use on greenhouse tobacco.
Bryan Dion, who runs an aerial crop spraying service based in Portage la Prairie, Man., called Jonair Ltd., has been in discussion with a group called the Mancozeb Task Force, which has been advocating for the continued use of mancozeb in potatoes and a number of other crops.
“Mancozeb is a very valuable product for use on potatoes. It’s cost-effective, and there is no known resistance to mancozeb in the world right now,” says Dion, who estimates that mancozeb spraying accounts for roughly 40 per cent of his business.
Dion maintains it’s not only companies like his that would be hard hit by the loss of mancozeb. The impact on potato growers, he says, would be considerable.
“They’d have to switch chemistries, which will cost them 40 to 50 per cent more. It’d be a significant increase in cost of production for the farmers,” he says.
Chlorothalonil is another Group M fungicide registered for use in potatoes in Canada (others include metiram, captan and copper). It recently underwent a PMRA re-evaluation which resulted in the allowable number of applications being reduced from seven to three per season. Dion says product availability issues in the past two of three years have caused chlorothalonil to double in price.