Potato virus Y in 2019 crop near lowest levels since regulatory caps began in 2011
Recent research presented at the N.B. Potato Conference and Tradeshow, Feb. 6th 2020, has highlighted the low levels of Potato virus Y (PVY) in the 2019 seed harvest in New Brunswick. The research was headed by Drs. Mathuresh Singh and Tyler MacKenzie of Potatoes New Brunswick’s Agricultural Certification Services (ACS) lab in Fredericton N.B. ACS is the primary lab for testing and certifying seed lots for the N.B. potato industry, and maintains an important ongoing research program testing best management practices for reducing PVY spread in the province.
Dr. MacKenzie’s recent presentation showed how PVY levels in the N.B. industry have dropped dramatically since 2009, and explained that the lower levels of PVY in the industry follow the instituting of strict regulatory limits on PVY in seed lots last decade, and careful in-field management by growers of this aphid-spread virus.
Average PVY level in all tested potato seed lots harvested in 2009 was 11.8%, which over a decade dropped to only 0.63% in the 2019 harvest. This is near to the lowest level ever measured in the N.B. potato industry, which was 0.43% in the 2016 harvest.
Average PVY in harvested seed lots in N.B. Averages for each year represent approximately 450 to 700 tested lots.
More important than the average PVY in the seed potato harvest, though, is the number of seed lots rejected due to PVY level exceeding the provincially-mandated virus cap. Currently, this cap for PVY is 4%, and harvested lots testing higher than this cannot be sold as potato seed in N.B. From the 2019 harvest, 98.1% of seed lots were below this threshold for rejection, near the record performance of the 2016 crop at 98.4% of seed lots accepted under the same strict virus cap.
Also important in the PVY trends in N.B. in recent years was the occurrence of a limited and temporary resurgence of PVY in seed potato lots in 2017-18. This event may have occurred because of an observed rise in aphid populations in those years, and an unusual number of volunteers sprouting in fields in 2017 as reported by some growers. In those years, average PVY in all tested lots briefly rose above 1%, before dropping again in 2019. This small burst of PVY spread, however, caused increased rejection of N.B. seed lots in those years, with accepted lots dropping to the 94-95% range. While the vast majority of seed lots still passed certification, this small increase in seed lot rejection represented up to an estimated $2 million of potential seed sales lost.
Thanks to close monitoring through the seed certification program in N.B. and diligent management of seed potato crops, this minor resurgence of PVY was detected and essentially eliminated by the 2019 crop year. With the completion of 2019 post-harvest testing at ACS earlier this winter, the potato seed certified for sale and planting of the 2020 crop is near best-ever in terms of PVY.
