Scab Resistant Potatoes

What is potato scab? It might sound a little unpleasant and it can look unpleasant too but it doesn’t appear to have any effect on the quality and taste of the potato. There are 2 types of potato scab, which are known as common scab and powdery scab. Both are types of fungal diseases that affects the skin of the potato causing rough and scabby patches. The thinner the skin, the more prone the potatoes are to infection. Potatoes that are infected with scab would not be saleable on a commercial basis although the potatoes are perfectly edible.

Common scab (Streptomyces var.) is the more serious of the 2 types of fungal infections, which can also affect other root vegetables such as swede, turnip and beetroot. Although the disease is often referred to by many as a fungus, it is more closely related to bacteria, which occurs naturally in some soil types. Common scab is more prevalent in dry conditions and on lighter soils, while powdery scab (Spongospora subterranean), is more often found on potatoes that are grown in heavier soils during wet conditions.  

Control methods for both types of potato scab

There are no chemical control methods available and so the only way to avoid infection is to take a few necessary steps to ensure prevention. One method is to ensure the soil is well prepared prior to planting seed potatoes. Incorporate plenty of well-rotted organic matter, which will help the potato plants grow strong and healthy and retain moisture levels. Applying water regularly during the growing stages is also vitally important especially as the plants begin to emerge.

It’s best not to save your own seed potatoes because even light infections of scab on seed potatoes can develop and affect the whole new crop. Other diseases can also be passed on from infected seed potatoes to new growing tubers. Common scab thrives in alkaline soils so avoid adding lime to the soil. If lime has been added to help prevent club root in brassicas then avoid growing potatoes in the same soil. Crop rotation can help new seed potatoes from becoming infected with scab.

Scab resistant seed potatoes  

The best way to avoid potato scab altogether is to select only scab resistant seed potatoes. If scab has been a problem in the past then this is the best option and there are many scab resistant varieties to choose from including Mayan Rose. This variety is a cross between Mayan Twilight and Mayan Gold. Another trusted, scab resistant variety is Nicola. This potato is considered a second early. It has long, oval tubers and is ideal for growing in potato bags or in deep containers. 

Other potato varieties with a high resistance to scab includes the popular King Edward and Pentland Javelin. The latter is a first early, heavy cropping potato that has a resistance to many diseases including blackleg. Vivaldi is another fine potato variety with high resistance to scab. This is a second early variety, which has yellow skin and pale yellow flesh. It’s delicious boiled, roasted, baked or mashed and is also low in calories and carbohydrates. Kestral is a variety of potato with a moderate resistance to scab alongside Gemson, Rocket, Arran Pilot and Maris Piper.     

How you found a better way of dealing with Potato Scab? Leave a comment below and let everyone know....

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