When you buy certified seed potatoes, also known as foundation seed, you’re buying a known variety of potato, guaranteed to carry minimum risk of disease. These potatoes are tested and certified by state organizations, usually connected with state departments of agriculture. Plain seed potatoes, by comparison, are not classified or certified by any organization. Eating potatoes, from the grocery store, are the poorest risk for planting. You don’t know the variety, whether they are diseased, or if a sprout inhibitor, which prevents normal sprouting in the bag (and in your garden), has been applied. A virus disease in a potato is not harmful to you when you eat it. It manifests itself when the plant is growing, and it is then trans- mitted by insects, usually aphids, and can ruin the crop.
So rely on good seed potatoes, not the grocery store, when planting. And unless you’re an experienced gardener, you might not want to plant back your own potatoes even long-time gardeners get caught with a disease out- break every once in a while.