Verticillium wilt............................................................
Fusarium wilt ................................................................
Wildings........................................................................
Cultivar mixtures ..........................................................
Off-types .......................................................................
Mild mosaic ..................................................................
Bolters ...........................................................................
2
2
2
1
1
1
1
Virus post control
6.
Samples for virus post control shall be taken in the field after haulm destruction. A
minimum of one thousand tubers per field shall be sampled.
7.
The determination of virus shall be done by serological methods and/or by occular
inspection. The result shall be given as a percentage by number of infected tubers.
Tuber control
8.
From each lot presented for tuber control at least five primary samples of a
minimum of forty tubers each shall be drawn. The primary samples mixed together shall
form the working sample to be examined. At least 500 tubers per seed lot shall be
examined.
9.
The working samples shall be washed, and all the tubers shall be cut through before
they are examined.
10. Diseased, damaged and severely mis-shaped tubers and tubers deviating in size from
the grade size shall be recorded as percentage by number; and the percentages found shall
be multiplied by the appropriate factors as set out in note 11 and the various products so
obtained shall be added together to give the defect index for the seed lot.
11.
The factors to obtain the defect index for the tuber control of a potato seed lot are as
follows:
Defect
Pink rot..........................................................................
Pythium rot....................................................................
Soft rot ..........................................................................
Spindle tuber .................................................................
Black leg .......................................................................
Fusarium .......................................................................
Phytophtora ...................................................................
Other dry rots ................................................................
Root knot nematodes.....................................................
Alternaria ......................................................................
Black heart ....................................................................
Black scurf ....................................................................
Sunscald ........................................................................
Tuber moth....................................................................
Cut worms.....................................................................
Factor
10
10
10
10
3
3
3
3
3
1
1
1
1
1
0.50