Potato growers should think seriously about treating potato seed against rhizoctonia, despite less black scurf this year, the Scottish Agricultural College’s Stuart Wale has advised.

“I’m confident that with closer inspection it wouldn’t take long to find symptoms. Surviving at low levels it will only take the right cool soil conditions next season to affect quality of the subsequent crop.”

The guideline threshold for seed treatment is 1% infection, but it can be difficult to certify crops are free from the disease, especially if relying on visual inspections, he added.

Liquid treatments were an alternative to on-planter dust treatments and could be applied to seed from November onwards, he said. But, they might be operationally difficult to introduce on some farms, he noted.

Certis’ technical officer Alan Horgan said seed treatments could be used with soil applications targeting soil-borne rhizoctonia infections, but this would not protect against seed-borne disease.

“If both a seed and soil treatment for rhizoctonia control cannot be justified, then protecting against seed-borne disease should take priority. Without robust seed protection, soil treatments could be wasted.”

Certis have launched a new technical guide for their RhiNo (flutolanil) seed treatment formulations. See www.certiseurope.co.uk