CLIMATE FACTORS INFLUENCING ATTACK OF COMMON BUNT (TILLETIA-CARIES (DC) TUL) IN WINTER-WHEAT IN 1940-1988 IN SWEDEN

The attack of common bunt (Tilletia caries) in winter wheat in field experiments performed during the period 1940-1988 has been correlated to climate data. The temperature during the period of days 1-11 after sowing (the germinating period) was strongly correlated to the frequency of infected spikes. The temperature after the emergence of the seedlings, the perciptation ann the duration of the snow cover were not correlated to the common bunt attack. The attack was strongest when the mean temperature during the critical period of days 1-11 after sowing was 6.7-degrees-C. A combined laboratory and field experiment with soil-borne infestation of common bunt showed that the frequency of infected bunt spikes was dependent on the environmental conditions a month after sowing, while the shortening of the straw was not dependent on these conditions. The shortening of the straw varied between different localities but not between different treatments at the localities.