Effect of fertilizer, fumigants, and fungicides on leafroll-net necrosis in Russet Burbank potatoes

A total of 112 combinations of 13 fumigants, fertilizers, and a fungicide was tested in replicated plots in eastern Washington in 1963 and 1964 to determine their effects on the net necrosis produced in Russet Burbank potatoes by the leafroll virus. Plots treated with Telone® (dichloropropenes) or Telone+chloropicrin had significantly fewer tubers discolored with leafroll net necrosis than untreated plots; plots treated with lower rates of various chlorinated propenes and propanes or ethylene dibromide had fewer discolored tubers than plots treated with higher rates of these chemicals; and plots treated with higher rates of various combinations of dichloropropenes with methyl isothiocyanate or 3-bromo-1-propyne had fewer discolored tubers than plots treated with lower rates of these chemicals. An interaction took place between the chemicals and the leafroll virus that either increased or decreased the amount of net necrosis in the tubers. Other types of internal discoloration (OID) in the tubers were significantly increased by Telone treatments in some tests. Telone treatments showed no effects on OID in other tests compared to untreated tubers. Also, nitrogen, at 100 lb/acre and over, significantly increased the other types of discoloration over no nitrogen, but potassium at 0 to 150 lb/acre and pentachloronitrobenzene (PCNB) at 0 to 30 gal/acre showed no significant effect.