The purpose of this program is to provide certification of Seed Potatoes of propagative stock now being produced by tissue culture and/or stem cutting techniques. Annually, new disease free stock is propagated for multiplication. There are restrictions on the number of seasons this seed may be planted back. For complete rules on Washington Certified Seed, see

Our seed potato growers are famous for growing and marketing quality seed. The isolated locations provide vigorous seed and deliver the product to you when you need it. 


All seed potatoes entered for certification shall be classified on the basis of production phases as follows:*

Generation Abbreviation Year(s) in the Field
Prenuclear PN 0
Nuclear N 1
Generation I G-I 2
Generation II G-II 3
Generation III G-III 4
Generation IV G-IV 5
Generation V G-V 6

*unless re-rated for exceeding tolerance rating 


(1) The quality of the grading of seed potatoes is the full responsibility of the grower. The Department of Agriculture shall monitor grading activities for compliance with the United States Standards of Seed Potatoes and established state standards for seed potatoes.

(2) Three colors of tags shall be permitted for use:

(a) Blue tags shall be used for seed potatoes which meet or exceed minimum requirements of United States Standards  for U.S. Number 1 grade of seed potatoes.

(b) Yellow tags shall indicate a contract between buyer and seller.

(c) White tags shall be U.S. Number 1 (1 oz. min./3 oz. max.)


(1) Zero tolerance is not intended, nor shall be construed, to mean that the lot inspected is free from the disease. In case of ring rot, nematode, or powdery scab, it means that the disease was not identified during any visual inspection.

(2) First and second field inspection tolerances, expressed as percentages.


Nuclear G1 G2 G3 G4 G5
Varietal Mixture 0.00 0.00 0.01 0.25 0.25 0.25
Mosaic 0.00 0.10 0.20 0.50 1.00 2.00
Leafroll 0.00 0.05 0.10 0.25 0.25 0.25
Total Visible Virus 0.00 0.10 0.30 0.75 1.25 2.25
Phytoplasmas 0.00 0.00 0.10 0.20 0.50 1.00
Black Leg 0.00 0.10 0.50 1.00 2.00 *
Ring Rot 0.00 0.00 0.00 0.00 0.00 0.00
Nematode 0.00 0.00 0.00 0.00 0.00 0.00
Spindle Tuber Viroid and other quarantined pests 0.00 0.00 0.00 0.00 0.00 0.00

* Tolerance for black leg does not apply to G5.
TR = Trace


The purpose of this test is to visually detect virus and virus-like plant symptoms in seed potato samples submitted by the grower. A seed stock that has more than a trace amount of virus disease noted during any field inspection shall not be recertified, unless it has been post harvest tested. All Generation 1 lots except lots that are less than .25 acre and planted back on the same farm, and all seed lots sold for recertification must also be post harvest tested.




Nuclear G1 G2 G3 G4 G5
Leafroll 0.00 0.25 0.50 0.75 1.00 2.00
Mosaic (well defined) 0.00 0.25 0.50 1.00 1.50 2.00
Total Virus 0.00 0.50 0.75 1.00 1.50 3.00



The 55th Legislature of the State of Washington found that the production of high quality certified seed potatoes within our state requires conditions that are free as possible from insect pests and plant diseases and that ensuring these conditions exist was in the public interest. Our legislature also recognized that the production of non-seed potatoes in close proximity to certified seed potatoes increased the risk that insect pests and plant disease will be introduced.

To mitigate this problem the Washington State Seed Potato Commission petitioned the Director of the Department of Agriculture requesting the establishment of a restricted seed potato production area. New rules were adopted prior to the 1998 growing season that formed a seed potato isolation district in Northwest Washington. Regulations for potato production within this isolation district require all potato plantings in excess of one acre to be enrolled in the seed potato certification program. The complete rules for this isolation district may be found in Chapter 16-325 Washington Administrative Codes.


Related Links Washington State Potato Commission National Potato Council Potatoes USA