Potato scab is caused by bacteria that infect the potato and cause parts of the vegetable to turn from a delicious vegetable into a dry, corky substance that looks unpleasant and tastes worse. Once your garden is infected with potato scab, it can also affect carrots and other underground legumes. Preventing potato scab is far easier than trying to rid the soil of this problem once it has taken hold, so taking these simple inhibiting measures now can save you a great deal of time and trouble later on.
Plant scab-resistant potatoes. Many varieties of potato have been developed naturally and artificially to resist potato scab. Plant these varieties in any field where there has been evidence of potato scab in the past. This will help block out the potato scab and still enable you to grow potatoes. You will need to plant these resistant potatoes for several years before re-introducing your original variety of potato.
Use acid-producing fertilizers. These fertilizers keep the pH of the soil around 5.0, which makes the soil highly inhospitable to the bacteria that cause potato scab. These fertilizers do not harm the potatoes and will not make them inedible or less safe for consumption. Avoid fertilizers that are high in lime or manure, and check with a local grower if you are not sure if the contents of a fertilizer will negatively impact your ability to consume the potatoes.
Plant corn or alfalfa in fields that have been hit hard with potato scab the previous season. This will "starve out" the infestation so that the next year you can start planting potatoes again.
Keep the soil highly moist. While it is very important that your potatoes not sit in the mud, which can cause them to rot, keeping a high level of moisture in the soil can encourage the development of moisture-loving bacteria that do not harm the potatoes and out-compete the bacteria that causes potato scab.