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.

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.

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®).

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).

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

Eighty-one monitoring plots within the Minidoka National Wildlife refuge on the Snake River Plain in south-central Idaho were surveyed in July-August from 2020 to 2023 to evaluate the effects of herbicides on the vegetation-community across areas that varied in both burn history and background cheatgrass abundance. Surveys consisted of line-point intercept measurements along two 6m or 50m transects with 100 points of observation per line. In spring of 2023 "escaped" cheatgrass individuals were counted in each 6x6m herbicide-treated plot.

Eighty-one monitoring plots within the Minidoka National Wildlife refuge on the Snake River Plain in south-central Idaho were surveyed in July-August from 2020 to 2023 to evaluate the effects of herbicides on the vegetation-community across areas that varied in both burn history and background cheatgrass abundance. Surveys consisted of line-point intercept measurements along two 6m or 50m transects with 100 points of observation per line. In spring of 2023 "escaped" cheatgrass individuals were counted in each 6x6m herbicide-treated plot.

Post-fire rehabilitation seeding in the U.S. Intermountain West, primarily conducted by the Bureau of Land Management, is designed to reduce the risk of erosion and weed invasion while increasing desirable plant cover. Seeding effectiveness is typically monitored for three years following treatment, after which a closeout report is prepared. We evaluated 220 third-year closeout reports describing 214 aerial and 113 drill seedings implemented after wildfires from 2001 through 2006. Each treatment was assigned a qualitative success rating of good, fair, poor, or failure based on information in the reports. Seeding success varied by both treatment (aerial or drill) and year. Aerial seedings were rated 13.6% good, 18.3% fair, 29.6% poor, and 38.5% failure. Drill seedings were rated as 30.1% good, 24.8% fair, 23.0% poor, and 22.1% failure. Logistic regression analysis found that aerial seedings were more successful with increasing elevation, long-term average precipitation, and precipitation received in the first and third years following treatment. Drill seeding success was best explained by elevation only, suggesting that these treatments are less sensitive to long-term average and precipitation received after treatment than aerial seedings. We found monitoring reports did not report seeding success consistently using quantiative objectives, control areas to proived adequate comparisons, and did not provide maps, making them difficult to assess spatially. Providing additional information in monitoring reports about important factors that can influence seeding success such as pre-fire vegetation would be useful for the creation of a decision analysis tool to aid land managers who are confronted with whether or not to perform post-fire rehabilitation treatments given limited resources and budgets.