Several types of disease and fungus may affect your seed potatoes after planting, causing them to rot in the ground instead of sprouting. Some areas are more prone to disease than others, and if you have successfully grown potatoes in the past with no problems, your seed potatoes likely don't require treatment. If you are starting a new potato bed or have had problem with rot and disease in the past, treating the seed potatoes just before planting helps ensure a healthy potato crop.
Cut your seed potatoes into 1- to 2-inch cubes, leaving at least one growing eye on each seed piece. Spread the seed pieces out on a disinfected baking sheet so the cut sides face up. Arrange the seed pieces so air is able to flow around them.
Place in a 50- to 55-degree F room for three to seven days. This allows the cut edges to seal over so they are less prone to infection.
Purchase the fungicide treatment that is recommended for your area's disease problems. It comes in either dust or liquid form. Mix the fungicide according to package directions.
Roll the seed pieces in dust fungicide until all sides are equally coated. Dip seed pieces in liquid fungicide to coat all sides. Wear gloves when treating seeds and wear a face mask as well if you are using a dust treatment.
Plant the seed pieces immediately after treating.