Prescribed burning followed by indaziflam enhances downy brome (Bromus tectorum) control

Abstract

B. tectorum (Bromus tectorum L.) is a highly invasive winter annual grass that can fill open niches in native plant communities. Prescribed burning is often used to control B. tectorum and can be combined with herbicide treatments to extend the duration of control and promote the native plant community. Several herbicides have been evaluated in conjunction with burning for B. tectorum control, although the herbicide indaziflam has not. In September 2017, two B. tectorum infested sites were burned in Colorado foothill shrublands. In March 2018, indaziflam was applied alone or in combination with glyphosate, rimsulfuron, or imazapic. These treatments were compared to imazapic plus glyphosate as a standard. All treatments were made within burned and non-burned areas in a crossed-nested design. Bromus tectorum cover and the desirable plant community responses were evaluated one and two years after treatment (YAT). In non-burned areas, all indaziflam treatments reduced B. tectorum cover compared to the control. In contrast, reductions from the imazapic treatments did not persist after the first year. Most post-burn treatments further decreased B. tectorum cover compared to the non-burned treatments. The most effective treatments (indaziflam 44 and 73 g ai ha−1 + imazapic 123 g ae ha−1) provided similar levels of control (< 1% B. tectorum cover 2 YAT), with or without burning. Desirable plant cover, richness, and diversity were not negatively impacted by burning or herbicide treatments. Plant diversity and species richness increased at Site 2 when burning was followed by indaziflam treatments. This study indicates that B. tectorum control using indaziflam can be enhanced when applied after burning, and the combinations with imazapic or rimsulfuron provide a wider application window compared to the combination with glyphosate.

Indaziflam reduces downy brome (Bromus tectorum) density and cover five years after treatment in sagebrush-grasslands with no impact on perennial grass cover

“…Land managers should be aware that short-term treatment outcomes may be inconsistent, and control may improve over time when using indaziflam alone, as was observed in our study. Seedorf et al (2022) observed more consistent short-term (1 to 2 YAT) B. tectorum control when tank mixing indaziflam with imazapic compared with applying indaziflam on its own, and imazapic consistently reduced B. tectorum abundance at 9 MAT in our study (Figures 1A and B and 2A and B). Coupled with its selectivity against annual grasses at low use rates (Kyser et al 2013), the short-term effectiveness of imazapic may make it a suitable tank-mix partner for indaziflam that can provide reliable short-term B. tectorum control.…”

“…At Site 1, the wildfire that occurred in August 2019 likely precluded our ability to detect treatment effects on perennial grass cover at 45 and 57 MAT. Our findings add to a growing number of studies demonstrating that indaziflam can selectively control annual grasses with minimal risk to established perennial plants (Clark et al 2019(Clark et al , 2020Fowers and Mealor 2020;Hart and Mealor 2021;Sebastian et al 2016Sebastian et al , 2017aSeedorf et al 2022), but future research should evaluate the potential for longer-term impacts to native perennials with repeated treatments. Impacts to P. spicata and A. tridentata seedlings have been observed in a grow room study (Clenet et al 2019), and grazing managers have long understood the importance of allowing perennial grasses to complete their reproductive cycles in at least some years (Burkhardt and Sanders 2012), which suggests that the potential for longer-term impacts from repeated indaziflam treatments may be different.…”

“…Researchers and land managers should also work together to determine how to best deploy indaziflam at landscape scales and combine indaziflam treatment with other practices (e.g., grazing to reduce fine fuels and safe sites for B. tectorum germination; Davies et al 2016Davies et al , 2021aPerryman et al 2020) and emerging restoration technologies (e.g., seed coatings and herbicide protection pods; Clenet et al 2019;Holfus et al 2021;Svejcar et al 2022). Along with other studies (Clark et al 2019(Clark et al , 2020Hart and Mealor 2021;Sebastian et al 2016Sebastian et al , 2017aSeedorf et al 2022), our findings suggest that indaziflam may allow land managers to achieve objectives that were not feasible with other management tools and that indaziflam can play a significant role in efforts to mitigate the devastating impacts of annual grass invasion.…”

Novel basal bark and cut stump herbicide treatments for Brazilian peppertree (Schinus terebinthifolia) management

“…A posttreatment statistical analysis was not performed for the mulched (LMU21) location due to lack of variation when all treated stems have 100% defoliation. The arcsine square-root transformation was used to normalize variance for old-growth (CX36) location percent defoliation with modifications suggested by Seedorf et al (2022) for treatments with complete defoliation. The ANOVA was performed by evaluation date and excluded treatments with 100% defoliation to accurately estimate the random block and residual error effects.…”

Incorporation of Indaziflam into Natural Areas Management of Cheatgrass and Other Short-Lived Invasive Species: Post-Fire Assessment in a Semi-Arid Colorado Grassland

“…Most available research on the interaction between fire and herbicide use is focused on timing prescribed fire to interact favorably with spray regimens (Simmons et al 2007; Calo et al 2012; Emery et al 2013). This includes recent work in a Colorado Foothills Shrubland showing that native plant diversity increased more in plots where indaziflam was applied after fall prescribed fire versus plots without fire (Seedorf et al 2022). Conversely, there is currently no information describing how pre-wildfire management with indaziflam shapes community assembly processes post-fire.…”