TRIALS OF MERCURIC CHLORIDE FOR THE PREVENTION OF POTATO SICKNESS

Abstract

SUMMARY An investigation of the effect on potato sickness of mercuric chloride applied as a soil dressing is described. It has been found that mercuric chloride applied 3–6 weeks prior to planting has a depressing effect on the early growth of potatoes. The variety Great Scot withstands this effect better than the varieties Majestic and Eclipse. This toxic effect is prevented by applying the chemical 3 or 4 months before planting. The degree of infestation of the plants by the eelworm is decreased by dressing the soil with mercuric chloride. The reduction in infestation is greater the nearer the application is to the time of planting. The reduction in eelworm infestation is accompanied by an increased yield of tubers except where plants cannot properly recover from the direct toxic effect due to mercuric chloride. Evidence has been obtained to show that mercuric chloride does not kill the eggs within the cysts. Mercuric chloride treatment of soil effectively prevents the fungous diseases common scab and collar rot. The writer wishes to acknowledge with thanks the assistance given by many of his colleagues, and especially to Mr W. E. Gelling and Mr J. Strachan for their help in arranging the field trials, and to Mr S. Burr and Dr W. A. Millard for their help with the mycological aspect of the investigation.