In vitro tests on the response of different Fusarium species to triadimenol fungicides showed a greater sensitivity in F.nivale and F.dimerum compared with other species which may be linked with their distinctive taxonomic grouping. The low incidence of F.nivale in the survey relative to that reported by earlier workers may be attributed in part to the more frequent application of fungicides to cereal crops in the field and the sensitivity of this fungus to the widely used triadimenol-containing formulations. A further factor accounting for the unexpectedly low incidence of F.nivale may have been the relatively mild winters and warm summers over the period of this survey which would be unfavourable to this low temperature fungus. From artificial inoculation of ears of different cereals with Fusarium species, F.culmorum, followed by F.avenaceum and F.graminearum were shown to depress grain yield significantly, F.culmorum having a major effect on grain size and the other two species causing a decrease in grain numbers. Earlier inoculations during the flowering period aggravated the effects of infection. The introduction of T.roseum 1 week before inoculation reduced these effects. The carry-over of ear inoculated Fusarium on seed was generally greater with the more pathogenic species, which also showed more deep-seated infection. However, the weak pathogen F.sambucinum also showed a high rate of carry-over and deeper penetration of seed tissues. Seed and soil inoculation tests confirmed that F.culmorum was the most pathogenic species, followed by F.avenaceum and F.graminearum. The addition of T.roseum to Fusarium inoculum adversely affected seed performance but other fungi, an isolate of Penicillum and of Cladosporium, reduced disease effects.