Chemical and biological control of Rhizoctonia solani on potato seed tubers

Chemical and biological treatments for the control of tuber-borne inoculum of R. solani on potatoes were evaluated by testing the viability of sclerotes removed from treated tubers. This technique showed that most sclerotes adhering to the tuber surface were devitalised when tubers were dipped for 20 min in a 2% solution of formaldehyde. Dusting tubers with toclofos-methyl, or spraying them with fenpiclonil or pencycuron, gave control equal to formaldehyde, whereas a sodium hypochlorite dip was ineffective. A spore suspension of Verticillium biguttatum applied to tubers as either a dip or a spray devitalised >90% of treated sclerotes, whereas similar treatments of other organisms such as Bacillus, Gliocladium, and Trichoderma were ineffective.