Differential aggressiveness of Bipolaris microstegii and B. drechsleri on Japanese Stiltgrass

Authors: Bruckart, William; Eskandari, Farivar; Thomas, Jami; Smallwood, Emily

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2017
Publication Date: 5/24/2017
Publication URL: https://handle.nal.usda.gov/10113/5801784
Citation: Bruckart, W.L., Eskandari, F., Michael, J.L., Smallwood, E.L. 2017. Differential aggressiveness of Bipolaris microstegii and B. drechsleri on Japanese Stiltgrass. Invasive Plant Science and Management. 10:44-52.

Interpretive Summary: Japanese stiltgrass is from Asia, and it is an invasive weed in the eastern United States. Two species of a fungus can make the plant very sick and even kill it. However, there is still a lot of Japanese stiltgrass that is not diseased in nature, so tests were made to see if all Japanese stiltgrass could be made sick when inoculated in the greenhouse. One of the pathogen species would infect Japanese stiltgrass from only one of six locations, so it was very limited as to which plants it could make sick. The other pathogen species caused disease on almost all of the Japanese stiltgrass, but the amount of disease was only moderate and may not be enough to use to control this plant. Both pathogen species caused disease on Japanese stiltgrass, but not on corn, sorghum, or deertongue, which is a native grass that grows with Japanese stiltgrass. These two pathogen species seem to be safe for use in controlling the Japanese stiltgrass, but they are either limited in which plants they infect, or they are not very damaging to the plant. More research is needed on these pathogens in order to determine if they will be effective in controlling Japanese stiltgrass.

Technical Abstract: Six populations of Japanese stiltgrass (JSG, Microstegium vimineum) were tested for susceptibility to both Bipolaris microstegii (5 isolates) and B. drechsleri (3 isolates), each capable of causing severe leaf blight disease in the field and each with potential for biological control of this species. Populations of JSG differed in their response to the two Bipolaris species, but within species of Bipolaris the plant responses were consistent. Only a population of JSG from Frederick, MD, was susceptible to B. microstegii; other populations from MD (3 locations), DE and IN sustained much less disease. In contrast, B. drechsleri caused disease on all accessions, but it was less aggressive compared with B. microstegii on the susceptible JSG accession. A limited host range determination with B. microstegii showed high levels of resistance in corn (4 cultivars, Zea mays) and sorghum (3 accessions, Sorghum bicolor). The native, sympatric grass, deertongue (Dicanthelium clandestinum) was not diseased in these tests. Use of these species for biological control does not seem practical without pro-active deployment, e.g., increase and spray application of the fungus. Capability to identify susceptible JSG will be needed for use of B. microstegii.