Field Inspections

Field inspections are important for any certification program because some diseases are more identifiable on the plant than on the tubers. This is the case with many strains of potato virus y (PVY), as well as potato leaf roll virus (PLRV). Furthermore, all lots considered for certification or re-certification by PCAN must be inspected during the plant growth stage (Figure 1).

Three field inspections are conducted annually by PCAN. First inspections are made in June, or once plants are capable of exhibiting symptoms. The following two inspections occur later in summer. This allows time for inspectors to identify problems not seen earlier in the season, including varietal mixtures.

Figure 1. It is required that all lots considered for certification or re-certification be inspected during the plant growth stage.

Figure 2. Various tolerances for diseases and varietal mixtures during field inspections.

Class Foundation Certified
Disease           Generation Prenuclear Nuclear 1 2 3 4 0 thru 5

Leaf roll

Mosaic

Total serious virus

Variety Mixture

0

0

0

0

0.1

0.1

0.2

0.1

0.2

0.2

0.4

0.2

0.3

0.3

0.6

0.3

0.4

0.4

0.6

0.4

0.5

0.5

0.6

0.5

1.0

2.0

3.0

0.5

Blights (Early and Late)

Visible Black Leg

Colombia Root Knot Nematode

0

0

0.5

0

0.5

0

0.5

0

0.5

0

1.0

0

3.0

0

Bacterial Ring Rot No tolerance allowed in any class or generation of seed

Commonly Asked Questions Regarding Field Inspections

What other conditions and/or diseases, not listed Figure 2, may disqualify a field or seed lot from being considered for certification/re-certification?

Any disease or condition seriously interfering with disease detection, such as wilt, weeds, yellowing due to soil conditions, excessive insects, hail injury, or chemical injury, may disqualify a field or lot from being considered for certification/re-certification.

What must a grower do if he/she wants to resample a rejected lot?

The grower, along with a certification official, collects 1,000 new tubers or leaves for testing. The cost for resampling is the responsibility of the grower.

What are the suggestions and/or restrictions regarding roguing?

Growers should start roguing as soon as plants are large enough to detect diseases. All diseased and weak hills should be entirely removed and destroyed, including seed pieces and new tubers.

If variety mixture or disease exceeds the tolerance at the time of inspection, the lot may be rogued to remove such plants, after which the field will be re-inspected for compliance. Any seed lot exceeding double the field tolerance for viruses of G5 (1.2%), shall be rejected and roguing will not be allowed.

Will the presence of early blight (Alternaria solani) or late blight (Phytophthora infestans) be a cause for the rejection of a lot?

The presence of solani and/or P. infestans may be cause for rejection only if present to the extent that satisfactory inspection cannot be made for other diseases.

What does NO TOLERANCE mean?

The wording NO TOLERANCE should not be construed as an expressed freedom from this disease.  It simply means there is no tolerance for this disease within the PCAN Rules and Regulations.