Monitor storages on a regular basis. Due to varying climate conditions, plants will likely be flowering at this stage in the West. Spraying may need to take place before flowering in Ontario and the Maritimes for maximum effectiveness. Contact fungicides should then be applied as required to the end of the season. Spraying foliage improves plant health and thereby reduces vulnerability to storage rots.
Fungicides are most effective when combined with good early management practices.
After harvest, if disease is suspected, due to unforeseen weather conditions or other uncontrollable factors, a fungicide such as Mertect can be applied, at the recommended label rate, directly onto the potato skin at the time of harvest. This practice has been shown to be highly effective in combating disease, with the exception being in certain regions where fungicide resistance has developed. Overuse of metalaxyl can result in resistance development. Based on my own observations, at least five percent of all lots are likely affected. Control of these diseases and prevention of the pathogens from developing fungicide resistance can be achieved by using broad spectrum fungicides prior to row closure and a systemic fungicide following row closure.