Optimizing efficacy of Bromus tectorum biological control in crops and rangelands
- Friday, April 7, 2017 at 8:30am
- Animal Biosciences Building, Room 138 - view map
LRES Ph.D candidate, Krista Ehlert will present her dissertation titled, " Optimizing efficacy of Bromus tectorum (cheatgrass, downy brome) biological control in crops and rangelands: feasibility, integration and implementation".
Management of Bromus tectorum L. (BRTE), an annual grass invasive in the western United States, has focused on single and integrated methods across crop and non-crop settings. However, extensive literature does not exist on the integration of Pyrenophora semeniperda (PYSE), a generalist grass pathogen for BRTE control. Pyrenophora semeniperda previously has been used experimentally with some success to control BRTE; however, questions remain about (1) the risk of non-target effects, (2) its efficacy as part of an integrated management plan, and (3) its efficacy under different environmental conditions and on different BRTE populations. I sought to answer these questions with three distinct studies. First, I assessed the risk of PYSE on BRTE and 15 economically important, co-occurring grass species in a greenhouse setting. P. semeniperda effectively reduced BRTE density by 40% and negatively affected 60% (9 of 15) of the non-target species tested, particularly native rangeland grasses. Second, I integrated P. semeniperda as part of a two-year rangeland revegetation management plan that included an herbicide (imazapic), a fungicide seed treatment, and different perennial grass seeding rates. Application of PYSE did not increase inoculum loads above ambient levels, and there was no effect of seeding rate or seed treatment. However, BRTE was reduced by 60% the first year with a single imazapic application. Lastly, I compared the efficacy of PYSE under a range of temperatures (13°C, 17°C, 21°C, 25°C, 32°C) for three distinct BRTE populations (range, crop, sub-alpine creek) using a temperature gradient table. Infection by PYSE peaked at intermediate temperatures (17°C, 21°C, 25°C) for the range and sub-alpine creek populations, but was generally low for the crop population at all tested temperatures. In general, BRTE germination decreased as temperature increased, but the range of decrease was greater for the control (15.6% to 38.9%) compared to the inoculated treatment (16.7% to 30.0%). Overall, my research indicated that BRTE control with PYSE is possible, provided (1) non-target effects are considered, especially for range species, (2) more research is conducted to increase PYSE inoculum loads above ambient levels and revegetation is used in conjunction with other control tactics, and (3) we take into account how distinct BRTE populations
- Department of Land Resources and Environmental Sciences