Q What are the warty nodules on my containergrown ‘Rocket’ potatoes?
Daphne Williams, Llanwnda, Gwynedd A Many gardeners will be familiar with potato scab which is caused by organisms similar to bacteria, resulting in rough, scabby patches on the tubers. It’s particularly common on dry, limey soils lacking organic matter. The symptoms on your potatoes are similar, but the warty, distorted growths point to a different disease known as powdery scab. It’s caused by a fungal infection and tends to be worse in wet conditions.
Tubers with either disease are fine to use, but they won’t store well. Both diseases can exist in the soil, but if you used potting compost in your containers, the disease may have come with an infected seed potato. ‘Rocket’ is susceptible to powdery scab, but if you’ve grown it successfully before, I wouldn’t be put off. If you’re looking for early maturing alternatives try ‘Accord’ or ‘Vales Emerald’.
Powdery scab on potatoes