Fusarium head blight, also known as scab, can be a devastating disease on all classes of wheat and barley. Among the species of Fusarium that cause scab, F. graminearum is the predominant pathogen. Wheat and barley are highly susceptible to infection when the crop is in the flowering to soft dough stages and when weather includes frequent precipitation, high humidity, or heavy dews. Multiple symptoms occur: reduced yields, discolored and shriveled kernels (tombstones), depressed seed weights, and reduced seed quality and vigor. The mycotoxin deoxynivalenol (DON, commonly known as vomitoxin) also can be produced by F. graminearum on infected grain. Grain contaminated with DON often is unsuitable for flour, cereals, or malt and is too toxic as feed for nonruminant animals (19). Distribution of Fusarium head blight. In recent years, Fusarium head blight has reemerged worldwide as a disease of economic importance (19). In the United States and Canada, the reemergence of Fusarium head blight in the 1990s has caused epidemics of varying severity on barley and on all classes of wheat. It is documented as causing epidemics in 26 states (19) and the Canadian provinces of Quebec (A. Comeau, Agriculture and Agri-Food Canada, Ste. Foy, Quebec, Canada, personal communication), Ontario (A

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Five isolates of Fusarium solani, originally isolated from diseased soybean roots in the Red River Valley (RRV) of Minnesota and North Dakota, were evaluated for their ability to cause symptoms on 10 genetically diverse soybean cultivars. Taproots of 2-week-old plants were inoculated with F. solani-infested oat kernels, and 3 and 10 weeks later, plants were evaluated for root rot and foliar symptoms. At 3 weeks after inoculation, taproots of all cultivars had extensive reddish brown to black lesions; root rot severity (1–6 scale) ranged from 4.8 to 5.1, and 3.5% of the plants had died. Foliar symptoms were not observed. At 10 weeks after inoculation, all cultivars showed extensive decay of taproots and >50% of lateral roots were necrotic; root rot severity (1–4 scale) ranged from 2.7 to 3.7, and 42.5% of the plants had died. Foliar symptoms were first observed between the R-1 to R-6 growth stages (about 5 weeks after inoculation) on the lower leaves and consisted of chlorosis at the margins that progressed inward. Veins initially were green, but leaves eventually became chlorotic, then necrotic, and fell with petioles still attached to the stem. In some cases, all of the foliage died. There was no significant (P = 0.05) isolate × cultivar interaction for root rot at 3 or 10 weeks after inoculation or for severity of foliar symptoms. Thirty-three cultivars commonly grown in southern Minnesota and the RRV were evaluated for reaction to one isolate of F. solani. Root rot severity ranged from 4.2 to 5.7 (1–6 scale) and 3.5 to 4.0 (1–4 scale), at 3 and 9 weeks after inoculation, respectively, and >50% of the plants died by 9 weeks after inoculation. Severity of foliar symptoms was low. These results indicate that isolates of F. solani from the RRV cause root rot and foliar symptoms on soybean and that cultivars grown in the region lack resistance to this pathogen. Foliar symptoms were not identical to those associated with sudden death syndrome.