The effect of potassium chloride on the infestation of sugar beet by beet eelworm, Heterodera schachtii Schmidt

Abstract

SUMMARYA high‐potassium compound fertilizer (N, 9 parts; P, 4 parts; K, 15 parts) increased sugar‐beet size and reduced the number of cysts of Heterodera schachtii on the roots: the same effects were induced by potassium chloride, and a smaller reduction in cyst number occurred after application of a standard compound fertilizer (N, 7; P, 3; K, 5·8 parts).Application of 0·1M potassium chloride solution 2 weeks before inoculation brought about the greatest reduction in infestation; the optimum invasion by eelworm occurred after KCl application at strengths between 0·01 and 0·001M.Larvae stimulated to emerge by leachates from potassium‐treated plants were more infective than those stimulated by control leachates. Leachates from potassium‐deficient plants induced quicker and cumulatively greater hatching of cysts than did leachates from plants receiving potassium. Where only part of the root system was grown in 0·1 m KCl solution, larval invasion in the untreated portion was lower than in controls. No indication of a relationship between potassium content and infestation was observed among lines of beet selected for high and low potassium content of ‘roots’ for processing, although there was a significantly reduced population of cysts in the high‐potassium plants. In the field, large doses of potassium chloride applied as top dressings reduced the reproduction of the eelworm to below the maintenance level: sugar content and yield of the marketable ‘roots’ were unaffected: potassium content was increased.