questions: asking about control of black scurf  
 answers: disease free seed tubers alone should be planted.
if there is a slight infection of black scurf that can be controlled by treating seed tubers with mercuric chloride solution for 1.5 hr with acidulated mercuric chloride solution for 5 min.
treating the soil with pentachloroni trobenzene at the rate of 70 kg/ ha lowers the incidence of the disease, but it is too expensive and cumbersome.
well sporulated tubrs may be planted shallow to control disease.
the disease severity is reduced in the land is left fallow for 2 years.