Utsädesbetningen med kvicksilverpreparat i Finland 1953 – 1968

Authors

• Hans Blomqvist Forskningsanstalten för växtsjukdomar, Lantbrukets forskningscentral, Dickursby

DOI: https://doi.org/10.23986/afsci.71763

Abstract

In Finland organic mercury compounds have been widely used since the end of the 1920s to control seed-borne fungus diseases of cereals. Because of their wide effective spectrum they still are dominating seed disinfectants for cereals giving good protection against the now important parasites Helminthosporium gramineum, Tilletia tritici, Ustilago avenae, and U. hordei, as well as the seed- and soil-borne Fusarium-infection. In the years 1953—68, 77 % of the bread grain seed and 39 % of all grain seed were treated with mercury disinfectants. Of the various dressing methods the one most widely used is dry seed dressing with preparations of the alkoxyalkyl (ethyl) type. The use of alkyl- (methyl-)mercury disinfectants, criticized on grounds of their toxicity to the fauna, has been small and in 1956—68 comprised only 5 % of all mercury seed dressings, calculated on the basis of the amount of active ingredients (fig. 1). Since 1969 only preparations of the alkoxyalkyl type have been sold. The strong criticism which was directed against seed dressing of cereals in the beginning of the 1960 led to a considerable decrease in the use of these chemicals. In 1963, about 640,000 hectares or 60 % of the cereal area were sown with mercury-dressed seed (fig. 2), while in 1967 the corresponding value was only 245,000 hectares or 21 %. This decrease in seed treatment resulted in increased frequencies of H. gramineum and T. tritici. According to the amount of active ingredients, in 1953—68 the total use of seed dressing mercury was 76 t or 4.8 t a year, of which only 3.5 t was alkylmercury. Most of this mercury reached the soils of southern and central Finland, where 87 % of the cultivated land is situated. In 1953—68, the annual addition of mercury from dressed seed to the cereal-growing soils was 4.7 g, and in relation to the whole cultivated area 1.8 g, of active ingredients per hectare (fig. 3). The amount of alkylmercury was 0.25 g and 0.1 g respectively. The epidemics of H. gramineum and T. tritici, which resulted from the marked decrease in seed dressing of cereals in Finland since 1963, show the need for a continued treatment of the seed. In this respect the mercury preparations are for the present the most effective. In trials with non-mercurial seed disinfectants, however, good protection has been achieved against certain seedborne fungal parasites. Evidently there will be a shift toward a more general use of the latter types of disinfectants in the future.