Comparative effectiveness of certain knife disinfectants and the use of the double-edged knife for the control of ring rot of potatoes

Summary

Tests using presumably ring-rot-free Red McClure seed potatoes in the San Luis Valley of Colorado in 1945 showed that boiling water and mercuric chloride solution (0.2 per cent) gave complete control of ring rot when used as rotary knife disinfectants. Solutions of Roccal (a mixture of alkyl dimethyl benzyl ammonium chlorides) in concentrations of 2, 1, and 0.5 per cent and Hyamine 1622 25 per cent (di-isobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride) in concentrations of 0.2, 0.1, and 0.05 per cent failed to give adequate control of ring rot when used as rotary knife disinfectants. Cresol (Phenol coeff. 5) in 2-per cent solution, although giving control, affected stand adversely. The stand was also markedly reduced following the use of a 1-per cent Cresol solution which, in addition, failed to give complete control of ring rot. Both 1-and 2-per cent Cresol solutions, when used without knife contamination, also resulted in highly significant stand reductions.

A newly designed stationary and automatically disinfected cutting knife gave control of ring rot which compared favorably with that obtained by the use of the power-driven rotary knife when both knives were disinfected with 0.2-per cent mercuric chloride solution.

When mercuric chloride solution (0.2 per cent) was used as a cutting-knife disinfectant, only a relatively small amount of infection was obtained by exposing the cut surfaces of seed pieces to contaminated platform boards at the base of the knife.