Beware of ‘unseen’ potato seed diseases

POTATO SEED that looks clean to the naked eye could still be harbouring microscopic disease-causing organisms and growers should get tubers tested, experts have warned.

Black scurf infection of 10-20% is common in potato seed and yet signs of the disease may not be visible on the surface, said Matthew Black from Harper Adams University.

“If this seed is left untreated the fungus is stimulated when the shoots emerge, causing weakened growth due to stem canker and black scurf blemishes on daughter tubers at harvest.”

He urges growers to get seed tested by methods such as the Harper Adams ‘Eye Plug Test’.

Unlike other diseases where treatment after infection is too late, applying seed treatments, such as RhiNo (flutolanil) will counteract the rhizoctonia organism, added Peter Shakespeare from Certis.

But he reminded growers that seed-borne infection will not be controlled by a soil treatment that is only active against rhizoctonia infection already present in the soil. “A seed treatment will stop infection being introduced to the soil and onto the crop.”