b'North Dakota Certified Seed Potatoes 2019 Crop Winter Grow Out ResultsBy Kent Sather, North Dakota State Seed Department, Potato Program DirectorA priority of a winter test grow-out for Inspectors returned to the plots for visual acresrepresentedthisyearareadirectcertified seed potatoes is estimating virus readingsJanuary6-20,2020.Resultsof result of unharvested acres. Fewer acreslevelsintheharvestedseeddueto readingsarecrucialtothegrower,and are estimated to be PVY free than pastasymptomaticlateseasoninfectionsof the industry, since they determine seed years. More PVY spread occurred in 2019PVY, also known as Mosaic. The virus can lots eligible for re-certification in 2020. than in 2018.PVY inoculum residing inbe transmitted between fields, say from Eligibility to re-certify depends on toler- commercialfieldsiseasilyvectoredbyan infected commercial field into a dis- ance limitations stated in North Dakota aphidstoadjacentornearbycertifiedease free certified seed field, or within a rules and regulations for certification of seedfields.Nonspecificaphidflightsfield. Since PVY is easily transmitted by seed potatoes. No more than 0.5% virus, from maturing grain crops and soybeansaphids anytime during summer growth, including PVY, is allowed in a seed lot to likely contribute to this increase.Whilethere may be an increased level of PVY in be planted for re-certification. these species of aphids are not efficientharvestedtubers.Summerinspections vectors of PVY, they still can vector theand leaf testing by trained North Dakota North Dakota certified seed growers sub- virus.GreenpotatovineslateintheState Seed Department (NDSSD) person- mitted 309 seed lots, representing 6,883 growingseasonalsoprovidepotentialnel provides information on how much acres of the 13,037 acres passing the 2019 targets for disease spread. viruswasplanted.Wintertestresults summerinspections.BasedonNorthindicate how much virus was harvested. Dakotaswintertestdiseasetolerances, Discernment is required for certified seedPVY is a yield limiting virus and therefore sample lots representing 4,055 acres were growers replanting seed lots in 2020. Lesshasatolerancerestrictionincertified deemedeligibleforrecertificationin acreageisavailableforrecertification,seed. It is the primary pathogen causing 2020. The only factor causing ineligibili- and of those acres, there is likely morerejectionofcertifiedseedpotatoesin ty of the remaining 2,828 acres was PVY seed borne PVY already present.North Dakota. incidence greater than the 0.5% virus tol-erance. AnelectronicversionoftheNorth2019 crop certified seed lots were sam- DakotaApprovedSeedListforpledbyNorthDakotaseedgrowersat Table 1 shows a historical comparison of Recertification based on the 2019 Cropharvest time. Samples were compiled by acresrepresented,eligible,andzero(0) winter test inspections can be found atNDSSD staff, shipped to Alger Farms, Inc. PVY percentages recorded at the winter www.ndseed.com underthePotatoatHomestead,Floridaandplantedby test. These are all significantly lower for Directory tab.NDSSDstaffNovember19-22,2019. 2019thanthepreviousyears.ReducedTable 1Crop Year Total AcresEligible% EligibleAcres %Represented Acres Acres 0 PVY 0 PVY2015 8,820 7,209 81 5,742 652016 8,338 6,797 82 4,881 582017 8,000 5,711 71 3,721 472018 8,045 5,545 69 2,834 352019 6,883 4,055 59 1,704 25MARCH 2020 POTATO GROWER 23'