USA: War over spud bug The United States has slapped a ban on potatoes from Prince Edward Island near Quebec in Canada after the potato wart fungus was found in a small section of one field. The US Department of Agriculture issued the ban eight weeks ago when the wart fungus was first discovered. Hopes that the ban would be lifted this week were dashed when the Americans said that they would open their borders to Prince Edward Island potatoes only if certain restrictions were accepted.