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Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum)
Rangeland Ecology & Management xxx (xxxx) xxx
Contents lists available at ScienceDirect
Rangeland Ecology & Management journal homepage: http://www.elsevier.com/locate/rama
Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum)* Daniel R. Tekiela* University of Wyoming, Laramie, WY 82071, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 August 2019 Received in revised form 9 October 2019 Accepted 11 October 2019
Downy brome (Bromus tectorum) is one of the most problematic invasive plant species in the United States. Downy brome invasions are associated with reductions in diversity and an increase in fire intensity. Bioherbicides that are reported to effectively control downy brome have been developed. Pseudomonas fluorescens strain D7 is one such bioherbicide that is of significant interest to land managers in Wyoming. A spatially replicated field trial was performed to identify what effect D7 has on downy brome in Wyoming. The field trial showed no response of any downy brome fitness metrics to D7; only commonly used synthetic herbicides were able to reduce downy brome cover. This work suggested D7 may not be a viable product for downy brome control, or more information may be needed about the field conditions required for a positive result when using D7. © 2019 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Key Words: cheatgrass invasive soil inoculation weed
Introduction Downy brome (Bromus tectorum) is one of the most widespread and problematic invasive plant species in the United States (Knapp 1996). Downy brome is associated with reductions in plant biodiversity and fitness (Gasch et al. 2013; Parkinson et al. 2013), reductions in wildlife habitat (Dumroese et al. 2015), and increases in fire risk (Bradley et al. 2018), among many other negative impacts (e.g., Melgoza et al. 1990). Due to the negative impacts associated with downy brome invasion, landscape managers continue to seek new strategies to remove downy brome and restore previously invaded habitats (Kelley et al. 2013). Bioherbicides have been a recent alternative tool of significant interest for downy brome control (Kremer and Kennedy 1996; Aston and Gorton 2015). In particular, the use of specific genetic strains of the soil bacteria Pseudomonas fluorescens has been reported to reduce the vigor and cover and downy brome among other invasive annual grasses (Gealy et al. 1996; Tranel et al. 1993, 2014). One such strain, D7, has been registered by the Environmental Protection Agency as a bioherbicide for use on downy brome in rangeland systems (EPA Registration 2014). Therefore, the
* This work was supported by the Pesticide Safety Education Funds Management Program (grant 0000000028) and USDA-NIFA-CPPM EIP (grant 2017-7000627281). * Correspondence: Daniel R. Tekiela, University of Wyoming, 1000 E University Ave, Laramie WY 82071, USA. E-mail address: [email protected]. (D. Augustine).
intent of this study was to identify the effect of P. fluorescens D7 on downy brome in Wyoming and determine if it may be a viable alternative to current management strategies. Methods To test the effect of P. fluorescens on downy brome, a field study was performed during the 2017 growing season. The product P. fluorescens D7 was used because it is the only current P. fluorescens product labeled for downy brome control. Because P. fluorescens is a living agent, prehandling of bioherbicide is more important when compared with synthetic herbicides to ensure it survives and can incorporate into the soil (D7 Label 2014). In all cases, the product was kept near freezing until just before application as is recommended. A replicated field test was performed in Albany, Goshen, and Laramie County, Wyoming. At each of the three sites, various combinations of the bioherbicide D7 and synthetic herbicides imazapic and indaziflam were applied to a preexisting population of downy brome at total solution volume of 187 L/ha with a six-flat fan nozzle boom (Table 1). To avoid any confounding issues with surfactants and to focus on preemergent activity, no surfactants were used with any treatments. Applications were applied to individual 3 m 9.1 m plots. Four replicates of each treatment were applied at each site. Applications occurred during November and December of 2016. Because D7 is a living biological product, application conditions were carefully monitored to ensure proper application (D7 Label 2014). Air temperatures were above freezing
https://doi.org/10.1016/j.rama.2019.10.007 1550-7424/© 2019 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Please cite this article as: Tekiela, D.R., Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum), Rangeland Ecology & Management, https://doi.org/10.1016/j.rama.2019.10.007
2
D.R. Tekiela / Rangeland Ecology & Management xxx (xxxx) xxx
Table 1 Untreated control, bioherbicide D7, and synthetic herbicides applied and their application rates for field trials occurring in Albany, Goshen, and Laramie Counties Wyoming. Herbicide
Rate product
Rate active ingredient
Untreated Imazapic Indaziflam D7 D7 D7 D7 þ Imazapic D7 þ Indaziflam
N/A 584 mL/ha 511 mL/ha 36 mL/ha (0.5) 73 mL/ha (1.0) 146 mL/ha (2.0) 73 mL/ha þ 584 mL/ha 73 mL/ha þ 511 mL/ha
N/A 140 g ai/ha 123 g ai/ha 5 1010 CFU/ha 1 1011 CFU/ha 2 1011 CFU/ha 1 1011 CFU/ha þ 140 g ai/ha 1 1011 CFU/ha þ 123 g ai/ha
CFU indicates colony forming unit.
and below 10 C during application. Conditions were overcast at each site due to oncoming precipitation, another recommended condition. At all sites, precipitation occurred within 48 h of application. At the time of application in Laramie (air temperature 0 C, ground temperature 4.5 C) and Albany County (air temp 2 C, ground temperature 4 C), no cheatgrass germination had occurred. At Goshen County (air temp 5 C), downy brome had, on average, three leaves per plant. In 2017 approximately 9 mo after treatment and in 2018 approximately 21 mo after treatment, percent cover data was collected to the nearest 1% for downy brome. Percent cover was collected across the entire plot for each year. A repeated measures analysis of variance was performed for all data using treatment as the explanatory variable nested within year, downy brome cover as the response, and site as a block using JMPv13. Means were separated using a Student’s t-test. Results Downy brome cover was significantly affected by herbicide treatments (P ¼ 0.0001). However, in 2017, only treatments that included imazapic significantly reduced downy brome cover below the untreated control (Fig. 1). D7 alone did not reduce downy brome cover when compared with the untreated control. In 2018, only combinations of synthetic and bioherbicides significantly reduced cover below the untreated control; however, these two treatments were not significantly different from the synthetic herbicides alone (Fig. 2).
Discussion P. fluorescens strain D7 did not decrease downy brome cover regardless of the application rate. Even at a 2 rate there was no effect on cheatgrass. This is contrary to results from the Pacific Northwest (Kennedy 2018, 1991). Most applications of P. fluorescens in Wyoming are in combination with synthetic herbicides with the belief that synergies occur between the two treatments. Unfortunately, there was also no synergistic effect when combining D7 and either of the synthetic herbicides. The effect was driven exclusively by the synthetic herbicide. Without information on the individual effect of the treatments, applications could continue with the belief that there was an “added effect” from D7. Thus, results from the study should be used to guide future downy brome management decision making. Bioherbicides unlike synthetic herbicides have special handling and application procedures to ensure the best chance of establishing the living agent into the soil microbiome. In all locations, these parameters were met as best as possible given the constraints of Wyoming weather conditions in 2016. Identifying a time window in which temperatures were appropriate (0 C10 C) and precipitation was imminent was difficult to meet in Wyoming. In 2017 precipitation did not come within that temperature window until late in the year when temperatures were near freezing and equipment failure due to freezing was possible. This made the window to apply D7 very small and possibly unrealistic for many land managers, regardless of its efficacy. This challenge may be seen across the western arid states where the required combination of precipitation and temperature could be difficult to find. This may not have been the case in Washington, where positive results have been shown (Kennedy 2018, 1991) and may also suggest additional differences in the environment that allowed D7 to reduce downy brome fitness. Further research is needed to identify the environmental conditions required to see the positive effects seen in Washington and avoid failed applications, such as was seen in this study. As microbial bioherbicides become more common, better information on the required environmental conditions to successfully use these products will become increasingly important. This information will help in identifying the ecological niche in which the bioherbicide may be effective. The challenging timing of application of D7 also made the window not overlap with the ideal timing for preemergent synthetic herbicides. Particularly at the site in Goshen County, downy brome
Figure 1. Response of downy brome percent cover to various synthetic herbicides and the bioherbicide D7 z1 yr after treatment. Ima is imazapic, and ind is indaziflam. Parenthetical numbers represent a relative application rate to recommended rates. Error bars represent standard error. Bars sharing the same letter do not statistically vary in their means.
Please cite this article as: Tekiela, D.R., Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum), Rangeland Ecology & Management, https://doi.org/10.1016/j.rama.2019.10.007
D.R. Tekiela / Rangeland Ecology & Management xxx (xxxx) xxx
3
Figure 2. Response of downy brome percent cover to various synthetic herbicides and the bioherbicide D7 z2 yr after treatment. Ima is imazapic, and ind is indaziflam. Parenthetical numbers represent a relative application rate to recommended rates. Error bars represent standard error. Bars sharing the same letter do not statistically vary in their means.
had already emerged when the application was applied, too late for a recommended timing of either imazapic and indaziflam to work effectively as preemergent herbicides. Typically, the application of indaziflam would occur at least 2 mo before germination to allow for soil incorporation via moisture (Sebastian et al. 2016), and imazapic requires at least some moisture to optimally work (Plateau label 2011). As previously mentioned, managers commonly apply tank mixes of bioherbicides and synthetic herbicides. If managers attempt to find an ideal time for bioherbicides, it may negate the efficacy of the synthetic tank mix partner. Synthetic herbicides did have an effect on downy brome. In particular, imazapic, a commonly used preemergent herbicide for downy brome control, did reduce cover alone and in combination with D7 one season after application. However, this effect did not persist into the second year (Elseroad and Rudd 2011). This shows the limited effect that some of the most common current chemical management strategies have and why managers still seek alternatives such as bioherbicides. Implications Downy brome management is still a challenge for many managers across the western United States. Unfortunately, P. fluorescens strain D7 did not have any effect on downy brome at multiple sites in Wyoming, making it unlikely to be an effective product in diverse environmental conditions. Unfortunately, synthetic herbicides did not offer long-term control either. This research shows why land managers have and will continue to seek alternative management strategies to deal with the continuing challenges of downy brome invasion. References Aston, L.M., Gorton, A.M., 2015. Scale-up trials using weed suppressive soil bacteria in rangeland restorationddesign, methods, and implementation: an experts’ workshop. US DOE, Washington, DC, USA.
Bradley, B.A., Curtis, C.A., Fusco, E.J., Abatzoglou, J.T., Balch, J.K., Dadashi, S., Tuanmu, M.N., 2018. Cheatgrass (Bromus tectorum) distribution in the intermountain western United States and its relationship to fire frequency, seasonality, and ignitions. Biological Invasions 20, 1493e1506. Dumroese, R.K., Luna, T., Richardson, B.A., Kilkenny, F.F., Runyon, J.B., 2015. Conserving and restoring habitat for Greater Sage-Grouse and other sagebrushobligate wildlife: the crucial link of forbs and sagebrush diversity. Native Plants Journal 16, 276e299. Elseroad, A.C., Rudd, N.T., 2011. Can imazapic increase native species abundance in cheatgrass (Bromus tectorum)invaded native plant communities? Rangeland Ecology & Management 64, 641e648. Gasch, C.K., Enloe, S.F., Stahl, P.D., Williams, S.E., 2013. An aboveground-belowground assessment of ecosystem properties associated with exotic annual brome invasion. Biological Fertility Soils 49, 919e928. Gealy, D.R., Gurusiddaiah, S., Ogg Jr., A.G., Kennedy, A.C., 1996. Metabolites from Pseudomonas fluorescens strain D7 inhibit downy brome (Bromus tectorum) seedling growth. Weed Technology 10, 282e287. Kelley, W.K., Fernandez-Gimenez, M.E., Brown, C.S., 2013. Managing downy brome (Bromus tectorum) in the Central Rockies: land manager perspectives. Invasive Plant Science Management 6, 521e535. Kennedy, A.C., 2018. Selective soil bacteria to manage downy brome, jointed goatgrass, and medusahead and do no harm to other biota. Biological Control 123, 18e27. Kennedy, A.C., 1991. Rhizobacteria suppressive to the weedy downy brome. Soil Science Society of America Journal 55, 722e727. Knapp, P.A., 1996. Cheatgrass (Bromus tectorum) dominance in the Great Basin desert. History, persistence, and influences to human activities. Global Environmental Change 6, 37e52. Kremer, R.J., Kennedy, A.C., 1996. Rhizobacteria as biocontrol agents of weeds. Weed Technology 10, 601e609. Melgoza, G., Nowak, R.S., Tausch, R.J., 1990. Soil water exploitation after fire: competition between Bromus tectorum (cheatgrass) and two native species. Oecologia 83, 7e13. Parkinson, H., Zabinski, C., Shaw, N., 2013. Impact of native grasses and cheatgrass (Bromus tectorum) on Great Basin forb seedling growth. Rangeland Ecology & Management 66, 174e180. Pesticides, B., 2014. D7 label. Northwest Agricultural Products, Pasco, WA, USA. Sebastian, D.J., Sebastian, J.R., Nissen, S.J., Beck, K.G., 2016. A potential new herbicide for invasive annual grass control on rangeland. Rangeland Ecology & Management 69, 195e198. Tranel, P., Gealy, D., Kennedy, A., 1993. Inhibition of downy brome (Bromus tectorum) root growth by a phytotoxin from Pseudomonas fluorescens strain D7. Weed Technology 7, 134e139. Tranel, P.J., Gealy, D.R., Irzyk, G.P., 2014. Physiological responses of downy brome (Bromus tectorum) roots to Pseudomonas fluorescens strain D7 phytotoxin. Weed Science 41, 483e489.
Please cite this article as: Tekiela, D.R., Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum), Rangeland Ecology & Management, https://doi.org/10.1016/j.rama.2019.10.007
Contents lists available at ScienceDirect
Rangeland Ecology & Management journal homepage: http://www.elsevier.com/locate/rama
Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum)* Daniel R. Tekiela* University of Wyoming, Laramie, WY 82071, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 August 2019 Received in revised form 9 October 2019 Accepted 11 October 2019
Downy brome (Bromus tectorum) is one of the most problematic invasive plant species in the United States. Downy brome invasions are associated with reductions in diversity and an increase in fire intensity. Bioherbicides that are reported to effectively control downy brome have been developed. Pseudomonas fluorescens strain D7 is one such bioherbicide that is of significant interest to land managers in Wyoming. A spatially replicated field trial was performed to identify what effect D7 has on downy brome in Wyoming. The field trial showed no response of any downy brome fitness metrics to D7; only commonly used synthetic herbicides were able to reduce downy brome cover. This work suggested D7 may not be a viable product for downy brome control, or more information may be needed about the field conditions required for a positive result when using D7. © 2019 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Key Words: cheatgrass invasive soil inoculation weed
Introduction Downy brome (Bromus tectorum) is one of the most widespread and problematic invasive plant species in the United States (Knapp 1996). Downy brome is associated with reductions in plant biodiversity and fitness (Gasch et al. 2013; Parkinson et al. 2013), reductions in wildlife habitat (Dumroese et al. 2015), and increases in fire risk (Bradley et al. 2018), among many other negative impacts (e.g., Melgoza et al. 1990). Due to the negative impacts associated with downy brome invasion, landscape managers continue to seek new strategies to remove downy brome and restore previously invaded habitats (Kelley et al. 2013). Bioherbicides have been a recent alternative tool of significant interest for downy brome control (Kremer and Kennedy 1996; Aston and Gorton 2015). In particular, the use of specific genetic strains of the soil bacteria Pseudomonas fluorescens has been reported to reduce the vigor and cover and downy brome among other invasive annual grasses (Gealy et al. 1996; Tranel et al. 1993, 2014). One such strain, D7, has been registered by the Environmental Protection Agency as a bioherbicide for use on downy brome in rangeland systems (EPA Registration 2014). Therefore, the
* This work was supported by the Pesticide Safety Education Funds Management Program (grant 0000000028) and USDA-NIFA-CPPM EIP (grant 2017-7000627281). * Correspondence: Daniel R. Tekiela, University of Wyoming, 1000 E University Ave, Laramie WY 82071, USA. E-mail address: [email protected]. (D. Augustine).
intent of this study was to identify the effect of P. fluorescens D7 on downy brome in Wyoming and determine if it may be a viable alternative to current management strategies. Methods To test the effect of P. fluorescens on downy brome, a field study was performed during the 2017 growing season. The product P. fluorescens D7 was used because it is the only current P. fluorescens product labeled for downy brome control. Because P. fluorescens is a living agent, prehandling of bioherbicide is more important when compared with synthetic herbicides to ensure it survives and can incorporate into the soil (D7 Label 2014). In all cases, the product was kept near freezing until just before application as is recommended. A replicated field test was performed in Albany, Goshen, and Laramie County, Wyoming. At each of the three sites, various combinations of the bioherbicide D7 and synthetic herbicides imazapic and indaziflam were applied to a preexisting population of downy brome at total solution volume of 187 L/ha with a six-flat fan nozzle boom (Table 1). To avoid any confounding issues with surfactants and to focus on preemergent activity, no surfactants were used with any treatments. Applications were applied to individual 3 m 9.1 m plots. Four replicates of each treatment were applied at each site. Applications occurred during November and December of 2016. Because D7 is a living biological product, application conditions were carefully monitored to ensure proper application (D7 Label 2014). Air temperatures were above freezing
https://doi.org/10.1016/j.rama.2019.10.007 1550-7424/© 2019 The Society for Range Management. Published by Elsevier Inc. All rights reserved.
Please cite this article as: Tekiela, D.R., Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum), Rangeland Ecology & Management, https://doi.org/10.1016/j.rama.2019.10.007
2
D.R. Tekiela / Rangeland Ecology & Management xxx (xxxx) xxx
Table 1 Untreated control, bioherbicide D7, and synthetic herbicides applied and their application rates for field trials occurring in Albany, Goshen, and Laramie Counties Wyoming. Herbicide
Rate product
Rate active ingredient
Untreated Imazapic Indaziflam D7 D7 D7 D7 þ Imazapic D7 þ Indaziflam
N/A 584 mL/ha 511 mL/ha 36 mL/ha (0.5) 73 mL/ha (1.0) 146 mL/ha (2.0) 73 mL/ha þ 584 mL/ha 73 mL/ha þ 511 mL/ha
N/A 140 g ai/ha 123 g ai/ha 5 1010 CFU/ha 1 1011 CFU/ha 2 1011 CFU/ha 1 1011 CFU/ha þ 140 g ai/ha 1 1011 CFU/ha þ 123 g ai/ha
CFU indicates colony forming unit.
and below 10 C during application. Conditions were overcast at each site due to oncoming precipitation, another recommended condition. At all sites, precipitation occurred within 48 h of application. At the time of application in Laramie (air temperature 0 C, ground temperature 4.5 C) and Albany County (air temp 2 C, ground temperature 4 C), no cheatgrass germination had occurred. At Goshen County (air temp 5 C), downy brome had, on average, three leaves per plant. In 2017 approximately 9 mo after treatment and in 2018 approximately 21 mo after treatment, percent cover data was collected to the nearest 1% for downy brome. Percent cover was collected across the entire plot for each year. A repeated measures analysis of variance was performed for all data using treatment as the explanatory variable nested within year, downy brome cover as the response, and site as a block using JMPv13. Means were separated using a Student’s t-test. Results Downy brome cover was significantly affected by herbicide treatments (P ¼ 0.0001). However, in 2017, only treatments that included imazapic significantly reduced downy brome cover below the untreated control (Fig. 1). D7 alone did not reduce downy brome cover when compared with the untreated control. In 2018, only combinations of synthetic and bioherbicides significantly reduced cover below the untreated control; however, these two treatments were not significantly different from the synthetic herbicides alone (Fig. 2).
Discussion P. fluorescens strain D7 did not decrease downy brome cover regardless of the application rate. Even at a 2 rate there was no effect on cheatgrass. This is contrary to results from the Pacific Northwest (Kennedy 2018, 1991). Most applications of P. fluorescens in Wyoming are in combination with synthetic herbicides with the belief that synergies occur between the two treatments. Unfortunately, there was also no synergistic effect when combining D7 and either of the synthetic herbicides. The effect was driven exclusively by the synthetic herbicide. Without information on the individual effect of the treatments, applications could continue with the belief that there was an “added effect” from D7. Thus, results from the study should be used to guide future downy brome management decision making. Bioherbicides unlike synthetic herbicides have special handling and application procedures to ensure the best chance of establishing the living agent into the soil microbiome. In all locations, these parameters were met as best as possible given the constraints of Wyoming weather conditions in 2016. Identifying a time window in which temperatures were appropriate (0 C10 C) and precipitation was imminent was difficult to meet in Wyoming. In 2017 precipitation did not come within that temperature window until late in the year when temperatures were near freezing and equipment failure due to freezing was possible. This made the window to apply D7 very small and possibly unrealistic for many land managers, regardless of its efficacy. This challenge may be seen across the western arid states where the required combination of precipitation and temperature could be difficult to find. This may not have been the case in Washington, where positive results have been shown (Kennedy 2018, 1991) and may also suggest additional differences in the environment that allowed D7 to reduce downy brome fitness. Further research is needed to identify the environmental conditions required to see the positive effects seen in Washington and avoid failed applications, such as was seen in this study. As microbial bioherbicides become more common, better information on the required environmental conditions to successfully use these products will become increasingly important. This information will help in identifying the ecological niche in which the bioherbicide may be effective. The challenging timing of application of D7 also made the window not overlap with the ideal timing for preemergent synthetic herbicides. Particularly at the site in Goshen County, downy brome
Figure 1. Response of downy brome percent cover to various synthetic herbicides and the bioherbicide D7 z1 yr after treatment. Ima is imazapic, and ind is indaziflam. Parenthetical numbers represent a relative application rate to recommended rates. Error bars represent standard error. Bars sharing the same letter do not statistically vary in their means.
Please cite this article as: Tekiela, D.R., Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum), Rangeland Ecology & Management, https://doi.org/10.1016/j.rama.2019.10.007
D.R. Tekiela / Rangeland Ecology & Management xxx (xxxx) xxx
3
Figure 2. Response of downy brome percent cover to various synthetic herbicides and the bioherbicide D7 z2 yr after treatment. Ima is imazapic, and ind is indaziflam. Parenthetical numbers represent a relative application rate to recommended rates. Error bars represent standard error. Bars sharing the same letter do not statistically vary in their means.
had already emerged when the application was applied, too late for a recommended timing of either imazapic and indaziflam to work effectively as preemergent herbicides. Typically, the application of indaziflam would occur at least 2 mo before germination to allow for soil incorporation via moisture (Sebastian et al. 2016), and imazapic requires at least some moisture to optimally work (Plateau label 2011). As previously mentioned, managers commonly apply tank mixes of bioherbicides and synthetic herbicides. If managers attempt to find an ideal time for bioherbicides, it may negate the efficacy of the synthetic tank mix partner. Synthetic herbicides did have an effect on downy brome. In particular, imazapic, a commonly used preemergent herbicide for downy brome control, did reduce cover alone and in combination with D7 one season after application. However, this effect did not persist into the second year (Elseroad and Rudd 2011). This shows the limited effect that some of the most common current chemical management strategies have and why managers still seek alternatives such as bioherbicides. Implications Downy brome management is still a challenge for many managers across the western United States. Unfortunately, P. fluorescens strain D7 did not have any effect on downy brome at multiple sites in Wyoming, making it unlikely to be an effective product in diverse environmental conditions. Unfortunately, synthetic herbicides did not offer long-term control either. This research shows why land managers have and will continue to seek alternative management strategies to deal with the continuing challenges of downy brome invasion. References Aston, L.M., Gorton, A.M., 2015. Scale-up trials using weed suppressive soil bacteria in rangeland restorationddesign, methods, and implementation: an experts’ workshop. US DOE, Washington, DC, USA.
Bradley, B.A., Curtis, C.A., Fusco, E.J., Abatzoglou, J.T., Balch, J.K., Dadashi, S., Tuanmu, M.N., 2018. Cheatgrass (Bromus tectorum) distribution in the intermountain western United States and its relationship to fire frequency, seasonality, and ignitions. Biological Invasions 20, 1493e1506. Dumroese, R.K., Luna, T., Richardson, B.A., Kilkenny, F.F., Runyon, J.B., 2015. Conserving and restoring habitat for Greater Sage-Grouse and other sagebrushobligate wildlife: the crucial link of forbs and sagebrush diversity. Native Plants Journal 16, 276e299. Elseroad, A.C., Rudd, N.T., 2011. Can imazapic increase native species abundance in cheatgrass (Bromus tectorum)invaded native plant communities? Rangeland Ecology & Management 64, 641e648. Gasch, C.K., Enloe, S.F., Stahl, P.D., Williams, S.E., 2013. An aboveground-belowground assessment of ecosystem properties associated with exotic annual brome invasion. Biological Fertility Soils 49, 919e928. Gealy, D.R., Gurusiddaiah, S., Ogg Jr., A.G., Kennedy, A.C., 1996. Metabolites from Pseudomonas fluorescens strain D7 inhibit downy brome (Bromus tectorum) seedling growth. Weed Technology 10, 282e287. Kelley, W.K., Fernandez-Gimenez, M.E., Brown, C.S., 2013. Managing downy brome (Bromus tectorum) in the Central Rockies: land manager perspectives. Invasive Plant Science Management 6, 521e535. Kennedy, A.C., 2018. Selective soil bacteria to manage downy brome, jointed goatgrass, and medusahead and do no harm to other biota. Biological Control 123, 18e27. Kennedy, A.C., 1991. Rhizobacteria suppressive to the weedy downy brome. Soil Science Society of America Journal 55, 722e727. Knapp, P.A., 1996. Cheatgrass (Bromus tectorum) dominance in the Great Basin desert. History, persistence, and influences to human activities. Global Environmental Change 6, 37e52. Kremer, R.J., Kennedy, A.C., 1996. Rhizobacteria as biocontrol agents of weeds. Weed Technology 10, 601e609. Melgoza, G., Nowak, R.S., Tausch, R.J., 1990. Soil water exploitation after fire: competition between Bromus tectorum (cheatgrass) and two native species. Oecologia 83, 7e13. Parkinson, H., Zabinski, C., Shaw, N., 2013. Impact of native grasses and cheatgrass (Bromus tectorum) on Great Basin forb seedling growth. Rangeland Ecology & Management 66, 174e180. Pesticides, B., 2014. D7 label. Northwest Agricultural Products, Pasco, WA, USA. Sebastian, D.J., Sebastian, J.R., Nissen, S.J., Beck, K.G., 2016. A potential new herbicide for invasive annual grass control on rangeland. Rangeland Ecology & Management 69, 195e198. Tranel, P., Gealy, D., Kennedy, A., 1993. Inhibition of downy brome (Bromus tectorum) root growth by a phytotoxin from Pseudomonas fluorescens strain D7. Weed Technology 7, 134e139. Tranel, P.J., Gealy, D.R., Irzyk, G.P., 2014. Physiological responses of downy brome (Bromus tectorum) roots to Pseudomonas fluorescens strain D7 phytotoxin. Weed Science 41, 483e489.
Please cite this article as: Tekiela, D.R., Effect of the Bioherbicide Pseudomonas fluorescens D7 on Downy Brome (Bromus tectorum), Rangeland Ecology & Management, https://doi.org/10.1016/j.rama.2019.10.007