Proliferation of cheatgrass and other exotic annual grasses such as medusahead and ventenata are a major environmental concern and operational problem for roadsides in Idaho. These annual grasses are highly flammable and they shorten fire-return intervals. Flammable vegetation is particularly hazardous in roadsides because of proximity to a ready source of ignition, and fires that start on roadsides can spread into adjacent public lands and urban communities with sprawling home development, causing extensive and expensive damage and degradation to wildlife habitat, rangelands, private or public property, utilities, etc. Thus, the Idaho Transportation Department (ITD) has a strong interest in preventing roadside vegetation from becoming invaded by exotic annual grasses and in improving vegetation on roadsides that are currently invaded, replacing exotic annual grasses with perennial bunchgrasses and forbs that support pollinators. These data were generated in roadside tests of various tools designed to reduce exotic annual grasses on the landscape, as well as techniques designed to improve the efficacy of these tools. These include the ACK55 strain of the bacterium Pseudomonas fluorescens, which was isolated to target cheatgrass, medusahead and jointed goatgrass (aka “weed-suppressive bacteria”, hereafter “WSB”). We also tested a relatively new pre-emergent herbicide, indaziflam (Rejuvra®) thought to remain active in soil for years after application. We tested these against and in combination with the “workhorse” pre-emergent herbicide most frequently sprayed by land managers for exotic annual grass control, Imazapic (Plateau®).

The exotic grass-fire cycle is degrading semiarid rangelands, such as the vast areas of shrub-steppe in North America now invaded by fire-promoting cheatgrass. Chemical- or bio-herbicides are sprayed onto soils to inhibit the invaders, but information on chemical- or bio-herbicide effects on plant communities is limited. We asked how the plant community responded to the bioherbicide Pseudomonas fluorescens strain ACK55 (Battalion Pro®) in comparison to the separate and combined effects of the most conventional pre-emergent chemical herbicide, imazapic (Plateau®), in two cheatgrass-invaded sagebrush-steppe sites. Plant community responses are compared with soil microbial community responses in the Larger Work, and soil microbial data are available in GenBank. Plant community responses are compared with soil microbial community responses in the Larger Work, and soil microbial sequence data were deposited to the NCBI Short Read Archive (BioProject PRJNA1254875).

Selective herbicide application is a common restoration strategy to control exotic invaders that interfere with native plant recovery after wildfire. Whether spraying with preemergent or bioherbicides releases native plants from competition with exotics (“spray-and-release” strategy) and can make communities resistant to re-invasion by exotic annual grasses (e.g., cheatgrass, medusahead), without risks to non-target native plants or secondary invasion, is a major question for land managers of semiarid plant communities. We applied chemical herbicides (imazapic, rimsulfuron) and weed-suppressive bacteria (Pseudomonas fluorescens strains MB906 and D7) to three different SW Idaho sagebrush-steppe communities after fire. We measured plant cover prior to burning and for four years after treatments.

Selective herbicide application is a common restoration strategy to control exotic invaders that interfere with native plant recovery after wildfire. Whether spraying with preemergent or bioherbicides releases native plants from competition with exotics (“spray-and-release” strategy) and can make communities resistant to re-invasion by exotic annual grasses (e.g., cheatgrass, medusahead), without risks to non-target native plants or secondary invasion, is a major question for land managers of semiarid plant communities. We applied chemical herbicides (imazapic, rimsulfuron) and weed-suppressive bacteria (Pseudomonas fluorescens strains MB906 and D7) to three different SW Idaho sagebrush-steppe communities after fire. We measured plant cover prior to burning and for four years after treatments.

Evaluating factors that affect recovery of canopy-forming, foundational species is needed to guide effective treatment implementation aimed at mitigating their loss due to the changing fire regimes being experienced in semi-arid shrub-steppe of the Western USA. Most inferences on factors influencing recovery are based on one-time measurements taken as a snapshot in time, usually focused on the short-term initial establishment phase or outcomes observed decades after. We measured factors associated with the secondary establishment of big sagebrush in nearly 2000 plots across a heterogeneous landscape five years after a megafire (115,000 ha) and the diverse mosaic of restoration treatments implemented and compare these findings to previously published inferences on initial, first-year germination patterns observed on the same plots.

We used Rangeland Condition Monitoring Assessment and Projection (RCMAP) maps of annual herbaceous fractional components (mostly invasive annual grasses) to calculate mean rate of change in invasive annual grass cover over five-year time periods. We also created a map that identifies zones of the sagebrush biome that could be prioritized for different management goals. The invasion of annual grasses has altered fire regimes and has contributed to the decline of sagebrush ecosystems. The vast expanse of annual grass invasions has required land managers to prioritize treatments in locations where they expect to be able to make a meaningful impact on invasion outcomes. Maps of invasive annual grass cover are useful in that they show the extent and severity of the invasion, but on their own, cover maps do not illustrate context such as how invasive cover is changing over time (i.e., increasing, stable, decreasing). The rate of change in invasive annual grass cover describes the trajectory of invasion. This information can be used by land managers to fine-tune priority locations and strategies for invasive species treatments in addition to other data sources (e.g., invasive annual grass cover maps).

We used Rangeland Condition Monitoring Assessment and Projection (RCMAP) maps of annual herbaceous fractional components (mostly invasive annual grasses) to calculate mean rate of change in invasive annual grass cover over five-year time periods. We also created a map that identifies zones of the sagebrush biome that could be prioritized for different management goals. The invasion of annual grasses has altered fire regimes and has contributed to the decline of sagebrush ecosystems. The vast expanse of annual grass invasions has required land managers to prioritize treatments in locations where they expect to be able to make a meaningful impact on invasion outcomes. Maps of invasive annual grass cover are useful in that they show the extent and severity of the invasion, but on their own, cover maps do not illustrate context such as how invasive cover is changing over time (i.e., increasing, stable, decreasing). The rate of change in invasive annual grass cover describes the trajectory of invasion. This information can be used by land managers to fine-tune priority locations and strategies for invasive species treatments in addition to other data sources (e.g., invasive annual grass cover maps).

Protection of intact habitat from the spread of invasive plants is a global priority, especially where the invaders alter wildfire occurrence. Invasion of perennial sagebrush-steppe ecosystems by cheatgrass and other fire-promoting exotic annual grasses (EAGs) is one of the most notorious examples of this problem. Protection and expansion of the remaining intact "core" habitat sagebrush areas are key management goals, and whether this can be accomplished by temporarily inhibiting annual plant populations with preemergent herbicides is a key question. We applied indaziflam in fall 2019 to replicate plots within two sagebrush-steppe sites in the Northern Great Basin, USA: 1) a relatively intact, uninvaded, unburned "core" site, and 2) a partially invaded site that burned in the 2015 Soda Wildfire. Vegetation cover, density, and growth responses of native perennials were measured annually to 2024. We asked whether our treatments "defended" and "grew" core sagebrush-steppe areas

Invasive-plant treatments often target a single or few species, but many landscapes are diversely invaded. Exotic annual grasses (EAGs) increase wildfires and degrade native perennial plant communities in cold-desert rangelands, and herbicides are thus sprayed to inhibit EAG germination and establishment. We asked how EAG-target and nontarget species responded to an herbicide mixture sprayed over a large, topographically diverse landscape after wildfire. We focused on how whole-community and natural EAG-pathogen treatment responses varied over years and physical properties of sites. We monitored plant cover and diversity in 41 pairs of plots located inside or outside areas (486 ha total) treated with a combined aerial broadcast spray of pre-emergent herbicide (imazapic) and weed-suppressive bacteria (Pseudomonas fluorescens, “MB906”) to target EAGs after wildfires in southwest Idaho, USA.

Invasive-plant treatments often target a single or few species, but many landscapes are diversely invaded. Exotic annual grasses (EAGs) increase wildfires and degrade native perennial plant communities in cold-desert rangelands, and herbicides are thus sprayed to inhibit EAG germination and establishment. We asked how EAG-target and nontarget species responded to an herbicide mixture sprayed over a large, topographically diverse landscape after wildfire. We focused on how whole-community and natural EAG-pathogen treatment responses varied over years and physical properties of sites. We monitored plant cover and diversity in 41 pairs of plots located inside or outside areas (486 ha total) treated with a combined aerial broadcast spray of pre-emergent herbicide (imazapic) and weed-suppressive bacteria (Pseudomonas fluorescens, “MB906”) to target EAGs after wildfires in southwest Idaho, USA.