FUSARIUM HEAD BLIGHT IN HARD RED SPRING WHEAT - CULTIVAR RESPONSES TONATURAL EPIDEMICS

Fusarium head blight (FHB), caused primarily by Fusarium graminearum S chwabe, is an important but sporadic disease throughout major spring w heat (Triticum aestivum L.) production areas in Canada and the USA. Ou r objectives were to (i) examine the effects of gears, planting dates, cultivars, and their interactions on FHB measures and agronomic trait s and (ii) characterize cultivar responses across a range of environme nts. Eight planting dates and 16 hard red spring wheat cultivars were studied in field trials during 1993 and 1994 at Crookston, MN. Normal and above-normal rain during June and July provided moist conditions d uring anthesis of most cultivars across several planting dates each ye ar. Incidence and severity of FHB varied markedly with planting date, anthesis date, gear, and cultivar. Cultivars that achieved higher than average grain yield and test weight over all environments did so beca use they performed well in environments that favored FHB. Cultivar mea n grain yield (r = -0.75 P = 0.01) and test weight (r = -0.93, P = 0.0 1) were inversely correlated with cultivar mean FHB incidence. 'Butte- 86,' 'Grandin,' 'Marshall' and 'Nordic' generally had lower mean FHB i ncidence and severity and were less responsive to environments favorab le for disease than other cultivars. These cultivars also had higher g rain yield and test weight than most other cultivars. 'Norm,' 'Minnpro ,' 'Sonja,' and 'Bergen' were representative of more susceptible culti vars. They had higher levels of disease, were more responsive to envir onments favorable for disease, and had low er grain yield and test wei ght. Attempts to avoid FHB by varying planting date were not successfu l. Careful cultivar selection for tolerance to FHB should provide mode rate increases in grain yield (10-20%) and test weight (5-10%) for spr ing wheat producers in northwest Minnesota.