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The PVY scourge: How new potato virus strains are troubling Maine farmers

The rise in rejected seed potatoes from last season’s crop can be blamed on new strains of an old virus, a Maine Potato Board plant pathologist said Tuesday.

The Maine Potato Board announced recently that 60 percent more seed potato lots tested in the 2019-2020 Maine Department of Agriculture, Conservation and Forestry’s annual post-harvest test were rejected than in 2018-2019. A total of 7.3 percent of all seed potato lots were rejected, Bangor Daily News reports.

It was the highest rejection rate for a Maine post-harvest test since 2012-2013. But the results were emblematic of a more significant problem experienced by farmers across the country: new strains of potato virus Y that are harder to spot during production than previous strains, Maine Potato Board plant pathologist Andrew Plant said.

More than 5 percent of the samples tested must be positive for either potato virus Y or potato leafroll virus in order for a lot to be rejected.

Plant, who tests crops from around Maine for viruses in the post-harvest test, said the primary cause of these rejections was recombinant strains of potato virus Y. He singled out potato virus Y strains N-Wilga and NTN, which he said have become more common within the potato industry in the past 10 years.

These new strains have displaced the previous cause of rejections — potato virus Y strain O. That strain had a higher likelihood of killing the potato plants it infected, but it was also far easier for growers to spot than more recent strains.

Plant said the high number of rejections, along with similar results across the country, would reduce the nationwide seed potato supply over the next few years.

Read the full report in the Bangor Daily News here

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Lukie Pieterse, Editor and Publisher

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