Epidemics of Fusarium head blight (FHB) occurred on barley in Minnesota, No
rth Dakota, and South Dakota from 1993 to 1998. The Red River Valley region
was most severely impacted by the disease based on assessments of FHB seve
rity in grain samples harvested from commercial fields. Fusarium graminearu
m was the primary pathogen causing these FHB epidemics. It comprised from 6
2 to 64% of all Fusarium species isolated from infected kernels from 1994 t
o 1996. Fusarium pone (range of isolation 13 to 20%), F. sporotrichioides (
10 to 17%), and F. avenaceum (6 to 10%) also were isolated from barley kern
els and were likely involved in causing some FHB infection, but to a very l
imited extent. All four Fusarium species were pathogenic on barley in inocu
lation tests conducted in both the greenhouse and the field. Mycotoxin scre
ens were performed on barley spikes inoculated with the respective species
in the greenhouse. Spikes infected with F: graminearum contained deoxynival
enol and 15-acetyldeoxynivalenol; those infected with F. sporotrichioides c
ontained T-2 toxin, HT-2 toxin, and T-2 tetraol; and those infected with F.
pone contained nivalenol. Some isolates of F: pone also produced 15-acetox
yscirpenol and scirpentriol. Although F. graminearum and DON are recognized
as the primary FHB pathogen and mycotoxin, respectively, in barley, the po
ssible presence of other Fusarium species and mycotoxins should not be over
looked.