Corky Scab is caused by bacteria Streptomyces scabies. It is particularly severe in dry periods. Affected potato tubers get scab lesions, which are quite variable, giving a raised corky area, or a pit.

To control corky scab:

• Keep potatoes well watered, especially during tuber set

• Aim for a soil pH of 5 or 5.2, by using acid producing fertilisers, such as ammonium sulphate. Do not lime or add manure before potatoes

• Grow resistant varieties

• Buy scab-free seed

• Rotate crops and have at least 4 clear years between potato crops on the same soil