An assessment of the need for routine use of organomercurial cereal seed treatment fungicides

Abstract

Abstract Seed crops need protection from a build-up of seed-borne pathogens, but it is not known whether such protection is necessary for the large proportion of seed which is sown to produce a crop for consumption. Trials have been carried out on farms in Scotland over a 5-year period to assess the risk of sowing untreated cereal seed. Over 220 comparisons were made, with 41 stocks of spring barley and 36 of winter wheat. The mean establishment of winter wheat was increased from 59% to 65% with treatment, but that of barley was not affected. The amount of seedling disease in untreated crops was approximately 2–3 times the level in treated crops. There were, however, no significant differences of overall mean yield associated with the absence of treatment for either wheat or barley. There were significant differences in yield in individual comparisons, but these were unrelated to significant differences in establishment or seedling disease, and they were considered to be due to intrafield variation, and not to the effect of treatment. It is considered that seed treatment to protect against seed-borne pathogens, other than wheat or barley loose smut if known to be present, is not necessary for certified seed being sown to produce a non-seed crop. The use of organomercury in seed treatments in Great Britain could be reduced from 17 to 6 tonnes per annum.