A fungal pathogen, Helminthosporium gramineum Rabehn f.sp. echinochloae (HGE), has been developed as a mycoherbicidal agent for the control of barnyardgrass in China. Under greenhouse conditions, the effect of the pathogen on disease incidence, mortality, and dry weight reduction of barnyardgrass was tested to determine the potential of this mycoherbicide. Field experiments during 2007 and 2008 showed that the conidia of HGE displayed excellent activity on barnyardgrass and good activity on a few other weed species. The HGE treatment increased the rice yield when compared with the untreated control and had no negative impact on the rice plant. In addition, the progression of HGE infection and the alteration of cellular ultrastructure in infected barnyardgrass were observed by using scanning and transmission electron microscopes. After infection, cell membranes of barnyardgrass leaves were found dramatically changed, and the ultrastructure of cells was severely deformed. This study clearly shows the scope of HGE as a potential mycoherbicide for control of barnyardgrass in agricultural cropping systems and has laid the groundwork for further studies on the mode of infection and the nosogenesis of HGE.

Nomenclature: Helminthosporium gramineum Rabehn f.sp. echinochloae (HGE); barnyardgrass, Echinochloa crus-galli (L.) Beauv.; rice, Oryza sativa L.