Assessment of the importance of seed cutting, in-season cultivation, and the passage of row equipment in the spread of PVYo in potatoes

Grower concerns, coupled with recent reports, have suggested that potato vi rus Y degrees (PVY degrees) may be spread as the result of mechanical trans mission following the cutting of infected tubers during seed multiplication , or through vine abrasion caused by the passage of row equipment used duri ng spraying operations and post-emergence tillage. We present the results o f a series of greenhouse and field experiments (on the potato cultivars 'Sh epody','Russet Norkotah','Russet Burbank','Jemseg', 'Kennebec', and 'Superi or') to examine this possibility. Our results provide no evidence to suppor t the view that mechanical transmission of PVY degrees occurs through the u se of (hand or mechanical) cutting knives. Statistical analysis of the spat ial pattern of in-field virus spread in the highly susceptible cultivar 'Sh epody' did not show a significant clumping of infected plants within plot r ows, arguing, in this case, that the passage of farm equipment and associat ed tillage operations are of no practical significance in the epidemiology of PVY degrees under growing conditions currently found in the Maritime pro vinces.