Fungal
Potato Scab
A soil-borne pathogen causing rough, corky, raised or pitted scabs on the skin of potato and beetroot tubers; plants remain healthy but tubers are blemished.
Symptoms to Look For
- Rough, raised or pitted corky patches on potato skin at harvest
- Scabs ranging from superficial russet to deep pitted lesions in severe cases
- No visible above-ground symptoms - plants grow and crop normally
Affected Plants
PotatoBeetrootParsnipRadishSwede
Organic Solutions
Water consistently during tuber set
Keep soil evenly moist for the 6 weeks after flowering begins - this is when tubers are most susceptible and dry soil greatly increases scab severity.
Acidify with pine needles or sulphur
Incorporate pine needle mulch or apply sulphur to lower soil pH below 5.5 - scab is significantly reduced in acid soils.
Prevention
- Grow scab-resistant varieties such as Maris Piper, Cara, or Sarpo Mira
- Avoid liming potato beds or applying fresh manure in the year before planting
- Rotate potatoes to a fresh bed each year as the pathogen persists in soil
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.