Curvularia eragrostidis isolates (Dematiaceae) for biocontrol of crabgrass (Digitaria spp.) in Canada

Abstract

ABSTRACT Large crabgrass (Digitaria sanguinalis (L.) Scop.) and smooth crabgrass (Digitaria ischaemum (Schreb.) Schreb. ex Muhl.) arrived into North America from Eurasia with immigrants as promising grain and forage crops, but they have become troublesome invasive weeds in cropland and turfgrass. Twenty-three foliar pathogens were isolated from crabgrass near Ste-Anne-de-Bellevue, QC, Canada and evaluated as potential microbial herbicides. Four Curvularia eragrostidis (Henn.) J. A. Mey., [Anamorph, (Meyer, 1959). Moisissures du sol et des litières de la région de yangambi (Congo belge). Publications de L'Institut Agronomique du Congo Belge, 75, 211 pp., Synonym of Cochliobolus eragrostidis (Tsuda & Ueyama) Sivan, Teleomorph, (Sivanesan, 1987). Graminicolous species of Bipolaris, Curvularia, Drechslera. Exserohilum and Their Teleomorphs. Mycological Papers, 158, 1–261] isolates were pathogenic on both large and smooth crabgrass. Two isolates with superior virulence proceeded to a host range assessment on 21 non-target grass species. Many plant species tested were not damaged, but timothy, creeping bentgrass, colonial bentgrass, and smooth bromegrass, were highly susceptible to these isolates. In addition, oats, millet, and sorghum were also susceptible. Susceptibility of these crops raises conflicts of interest and highlights the non-target risks of proceeding with the development of this microbial herbicide. Contra-wise these forage grass species are also recognised as undesirable invasive weeds in native North American grasslands. When the efficacy of Canadian isolate Dip0307 was compared to C. eragrostidis QZ-2000 bioherbicide from China, there was no difference in the control of large crabgrass. Further studies with the isolates are needed to verify their microbial herbicide potential for crabgrass suppression. Resolution of any conflict of interest will require consultation amongst various stakeholders, and if there is an apparent conflict, this needs to be resolved, if not beforehand then at least in parallel with any further studies.