Pests & diseases › Scab (Potato/Apple)
Scab (Potato/Apple)
Common scab (potatoes) and apple scab — different organisms with similar names. Both cause rough corky lesions.
Symptoms
- Potatoes: corky, rough, raised patches on tuber skin
- Apples: olive-green velvety spots on leaves, brown-black scabs on fruit
- Pears: similar dark scabs
- Yields rarely affected on potato (peel and eat); apple fruit unsellable
Lifecycle
Potato: bacteria persist in soil. Apple: fungal spores overwinter on dropped leaves.
What to do
- Potato: no in-season treatment, dig and use as normal
- Apple: rake and bag all fallen leaves to break disease cycle
- Sulfur sprays on apples
If it's bad
- Captan or myclobutanil on apples during spring growth
Stop it coming back
- Potato: don't lime soil, keep pH 5.5–6.5, water consistently when tubers forming
- Potato: resistant varieties: Russet Burbank, King Harry, Dark Red Norland
- Apple: resistant varieties: Liberty, Goldrush, Enterprise, Pristine
Crops it goes for
Plan the plot, track every sowing, cook the harvest
Sowing reminders and harvest forecasts for your own frost dates, the Seed Tin, Scan Centre for any label or packet, and the Potty Mouth Garden Club. Free to start.