Evidence of Potato virus Y Spread through Post-Emergence Management Practices in Commercial Potato Fields

Potato virus Y (PVY) transmission was studied in six commercial potato fields in 2015 and 2016 in New Brunswick, Canada. Plants emerged from PVY-positive tubers, or PVY-free plants that were artificially inoculated with PVY shortly after emergence, were used as PVY inoculum plants in the study. In all trials, equal numbers of PVY inoculum plants from each of three strains common in the region, PVY O , PVY N:O and PVY NTN , were used. PVY inoculated into tractor-traffic rows showed 2 to 7 times as much PVY spread to previously virus-free plants by the end of the season (up to 48.5% in one tractor row, compared to a maximum of 16.3% in a distant control row unaffected by tractor traffic). Evidence supporting a hypothesis that tractor traffic enhances PVY transmission through aphid disturbance was observed by PVY spread in both directions along the rows, not biased in the direction of tractor travel, and that the ratio of spread of the three strains was nearly indentical in control and tractor rows. However, the lack of spread to immediately adjacent rows, and statistically significant spatial pattern matching the circumference of tractor wheels specific to each field support the hypothesis that direct mechanical transmission of wounded plant sap could also be a factor in the enhanced PVY transmission.