The in vitro effect of allelopathy and various fungi on marsh reed grass (Calamagrostis canadensis)

Abstract

Allelopathy and endophytic fungi were evaluated as factors affecting the biological control of marsh reed grass, Calamagrostis canadensis (Michx.) Beauv., a weed of boreal reforestation areas. Leachate from marsh reed grass straw inhibited root growth into liquid and agar media and increased foliar necrosis. Most seedlings harboring endophytic species of Fusarium and Chaetomium were healthy in agar controls, but all such seedlings were diseased when grown in agar with straw leachate. The straw leachate and various fungi had distinct impacts on the virulence of Colletotrichum sp., a potential biocontrol agent for marsh reed grass. In comparisons of control and allelopathic media, Colletotrichum sp. stimulated the overall vigor of reed grass while reducing vigor in the allelopathic medium. Individual isolates of fungi in the genera Epicoccum, Drechslera, and Fusarium were uniformly antagonistic to Colletotrichum, whereas antagonism in individual isolates of Chaetomium, Alternaria, and Stemphylium depended on the presence or absence of allelopathy. Another Fusarium isolate increased the virulence of Colletotrichum sp. in both media, as did two applications of Colletotrichum sp. Allelopathic compounds, Fusarium sp., and Colletotrichum sp. are potential components of a strategy for biological control of marsh reed grass. Key words: weed, biological control, bioherbicide, mycoherbicide.