DWARF BUNT (TILLETIA-CONTROVERSA KUHN) IN WINTER-WHEAT IN SWEDEN - RELATIONSHIP TO CLIMATE (1951-1987), CLIMATE, SURVEY RESULTS AND CULTIVATION MEASURES (1967-1987)

During the period 1977-1987, 2132 samples of winter wheat kernels were selected at random and analyzed for occurrence of Tilletia contraversa spores. The share of samples with more than 100 T contraversa spores per gram winter wheat was 1 % in the southern + the western region. 19 % in northern Kalmar (H) county, 17 % in the island of Gotland and 8 % in the cm of thc middle of Sweden. During the period 1968-1987, an average of 61 samples of winter wheat kernels was annually selected at random from die island of Gotland. The frequency of T contraversa spores found in these samples was positively correlated with the number of infected plants in the untreated plots in the field experiments, with the duration of snow cover, with the number of days in dic autumn with a temperature below 0-degrees-C and was negatively correlated with the mean temperature in December. There was no clear correlation between die frequency of T contraversa spores in the kernel samples and the following factors: the interval between harvest 2nd sowing of winter wheat, the sowing time, the mean temperature or temperature fall during days 11-50 after sowing, the precipitation during the autumn, the temperature during the months January-june, the per cent of winter wheat area ploughed in the spring or the winter wheat stand in May. Analysis by multivariate methods has not explained the investigated relationships better than conventional statistical methods.