Our potatoes this year aren’t as perfect as they could be due to scab disease, all the little brown bumps on the skins. Potato scab is caused by a common bacteria found in soil There are plenty of good references discussing scab, its causes and prevention, like Vegetable: Potato, Scab | UMass Center for Agriculture, Food and the Environment and Potato Scab (cornell.edu). Scabby potatoes are edible, but the scabby parts should be peeled, which reduces the nutritional value.
A summary of how we can reduce the risk of scab on our spuds:
- Grow scab-resistant varieties, such as Superior, Russet Burbank and Red Norland, and others listed in the references. We’ve had pretty good results with Red Norland in the past. We should always check our selections for scab-resistance.
- Buy certified scab-free seed potatoes from reputable sources. We do that.
- Keep the soil pH below 5.2. We really can’t do that because of our crop rotation, unless we want to juggle sulfur and lime ever year and do a lot of soil testing. Most of our other crops do best in a pH of 6.0-7.0, and would suffer in acidic soil.
- Keep the beds well watered in the 2-6 seeks after planting. We can do that.
- Minimize organic soil amendments, which encourage scab growth. So we shouldn’t add compost or manure to our potato beds.
- Don’t plant potatoes in the same bed more often than every three years. Our crop rotation does that.