22 August 1997

Hidden scurf peril

BLACK scurf can hit potato production even if symptoms of the skin blemishing disease do not show.

That is one of the first findings in a major SAC project which aims to rationalise chemical applications in potato crops. The work, funded by the British Potato Councils grower levy, looked at Maris Bard seed stocks with different levels of black scurf infection.

Initial results indicate that even at low levels (0.8% of tubers), infection can hit tuber size, said SAC crop biologist Rob Clayton. This was also apparent in seed with 2.5% infection. But symptoms only become apparent when 7% of seed tubers are infected.

"The trial is in its early stages and we only lifted a small area of crop for this open day. But the signs are that levels of infection will cause great variation in tuber size," said Dr Clayton.