SURVEY OF COMMON BUNT (TILLETIA-CARIES (DC) TUL) IN WINTER-WHEAT DURING THE PERIOD 1967-1987 IN SWEDEN

During the period 1967-1987, an average of 269 samples of winter wheat kernels have annually been selected at random. The frequency of Tilletia caries spores found during the different years is positively correlated to the number of infected spikes in the untreated plots of the seed-dressing experiments. In spite of the general use of seed dressing in winter wheat, there was a residual contamination of spores on the kernels. This residual contamination increased slightly but significantly when the conditions were especially favourable for infection. The per cent of samples (Y) of wheat with > 500 spores/g kernel increased with the number of infected spikes/m2 (X) in the untreated plots in the field experiments according to the equation Y = 0.9 + 0.015 * X; r = 0.52 *. During the years 1977-1987, the portion of samples with more than 500 spores/g winter wheat was in the south + west regions 1 %, in northern Kalmar (H) county 2 %, on the island of Gotland (I) 3 % and in the middle east of Sweden 3 %.