TESTING POTATO seed tubers for Rhizoctonia before planting is still worthwhile despite relatively low disease risk this season, growers are told.

While cool, wet conditions last summer have reduced disease pressure in general, some samples are still showing problems, said National Institute of Agricultural Botany‘s David Kenyon.

Some 40% of samples tested in Scotland this winter showed evidence of black scurf, according to the Scottish Agricultural College.

“In the absence of any scientifically-based economic threshold for treatment, growers should be going in with as clean a tuber as possible to avoid introducing the disease,” said Dr Kenyon.

A general guide is that if one in 100 tubers are showing black scurf, then seed treatment can be justified, added the SAC‘s Stuart Wale.

In many cases, Rhizoctonia symptoms cannot be detected by eye and testing can help growers decide whether seed treatment is warranted, noted Bayer CropScience technical manager, Nigel Adam.

He recommends using the Monceren (pencycuron) product range to treat seed and prevent potential contamination of soil.

“Preventing disease symptoms caused by infected soil is a good deal more difficult and expensive than preventing disease originating from infected seed,” he said.