An examination of systemic infections of Fusarium culmorum on winter wheat in Schleswig-Holstein

In north-west Germany Fusarium head blight of wheat (FHB) is frequently caused by Fusarium culmorum and F. graminearum. This damage has, however, mainly been caused by infections during flowering; the incidence of FHB has increased steadily for many years in crop rotations without maize. The authors postulate that F. culmorum can cause systemic infections in wheat. In 2003 they used real-time PCR to analyse more than 1 100 tissue samples from wheat fields in order to determine whether F. culmorum was present in the internodes and spikes of the wheat plants. More than 30% of all analysed samples contained F. culmorum-DNA, and many wheat stems were completely or nearly completely systemically colonized by F. culmorum. These findings are consistent with those of other researchers who have detected a systemic growth of F. culmorum during experiments under controlled conditions. It cannot be automatically assumed that the fungus spreads from the wheat head during flowering; the plant could have become infected through chlamydospores or mycelium on residual plant debris in the soil. Therefore this pathogen must be regarded as a crop rotation disease. F. culmorum is able to severely infect wheat through the roots and stem bases, especially when the soil is dry and warm. Thus, spraying fungicides during flowering is ineffective. © Springer-Verlag 2006.