Progress 07/01/10 to 06/30/15
Outputs
Target Audience:Each project objective has a different target audience. A. The target audience for this objective has been canal operators, water operators and county, state, and federal water managers. I have also done programing that focuses on private lake management. B. The target audience for this objective has been other CSU researchers with interests in herbicide resistant weed management and herbicide resistance mechanisms. I have also been involved in extending research finding to stakeholder audiences. C. The target audience for this objective has been private, county, state, and federal land managers. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Based on these objectives, I became involved in two organizations, the Tamarisk Coalition and the Aquatic Plant Management Society. The Tamarisk Coalition holds a meeting each year that alternates between research and extension/outreach. I have participated in these meeting for the past seven years as a learner and as an educator. The Aquatic Plant Management Society provided many opportunities for professional development and graduate student support. How have the results been disseminated to communities of interest?Research results have been published as journal manuscripts and as one book chapter. At the same time this information has been distilled into more site specific management strategies and presented at a variety of extension/outreach meetings. The Tamarisk Coalition meeting has been the main source for disseminating results related to tamarisk research. The results of research focused on aquatic plant management has been provided to a number of organizations primarily at the request of County Extension Educators. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Control strategies for Eurasaian watermilfoil, sago pondweed and horned pondweed were evaluted and information on herbicide behavior was developed. This information was specific to Colorado conditions and provided to stakeholders with research based information that would allow them to make informed management decisions. For tamarisk, this project developed site specific information on the ecological impacts of various management strategies. These data were specific to the Arkansas River watershed, which accounts for about 70% of all the tamarisk in Colorado. Information was also developed on the impacts of herbicide treatments on passive restoration.
Publications
- Type:
Book Chapters
Status:
Published
Year Published:
2013
Citation:
Douglass, C. H., S. J. Nissen, and C. R. Hart. 2013. Tamarisk Management. in Tamarix: A Case Study of Ecological Change in the American West, eds A. Sher and M. F. Quigley. Oxford University Press
ISBN 978-0-19-989820
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Vassios, J.D., S.J. Nissen, T.J. Koshnick, and M.A. Heilman. 2014. Triclopyr absorption and translocation by Eurasian watermilfoil (Myriophyllum spicatum) following liquid and granular applications. Weed Sci. 62:22-28.
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Douglass, C.H., S.J. Nissen and A.R. Kniss. 2016. Efficacy and environmental fate of imazapyr from directed helicopter applications targeting Tamarix species infestations in Colorado. Pesticide Manag Sci. 72:379-387.
- Type:
Journal Articles
Status:
Awaiting Publication
Year Published:
2016
Citation:
Douglass, C.H., S.J. Nissen, P.J. Meiman, and A.R. Kniss. 2016. Impacts of imazapyr and triclopyr soil residues on the growth of several restoration species. Rangeland Ecology and Management (in press)
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: County, state, federal land managers and private land owners Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? This research project provided the training and professional development for a graduate student, results from this research were a major part of her thesis and have been submitted for publication. A number of undergraduates were also involved in this project and received training. How have the results been disseminated to communities of interest? Research results have been presented at a professional meeting that was attended by state and federal land managers, as well as contractors involved in large scale restoration projects. What do you plan to do during the next reporting period to accomplish the goals? During the next reporting period I plan to develop a more detailed approach to downy brome management that will involve multiple years of control and should reduce and potentially eliminate downy brome from the soil seed bank.
Impacts
What was accomplished under these goals?
Downy brome (Bromus tectorum L.) is a highly successful invasive species primarily because it fills an open niche in native plant communities. It also produces large amounts of litter over time. We hypothesized that removing accumulated litter with a prescribed burn before applying herbicides would improve herbicide efficacy, extending the duration of control. In January 2012, two downy brome infested sites were burned. In March 2012, post-emergent applications of glyphosate, imazapic, and tebuthiuron were made in a split-plot design. Aboveground biomass was collected at 6, 18 and 27 months after treatment (MAT) to evaluate treatment effects. In non-burned areas, all herbicide treatments were similar to the control 27 MAT; however, burning combined with imazapic or tebuthiuron still reduced downy brome biomass by 81% ± 4.55 SE and 84% ± 19.33 SE, respectively. Remnant species responded positively to burning and herbicide treatments. Cool season grass biomass increased after burning, while warm season grass biomass increased following tebuthiuron treatments. The impact of litter on imazapic and tebuthiuron availability was also evaluated. Herbicide interception increased in a linear relationship with increasing litter. For every 50 g·m-2 increase in litter there was a 7% increase in the amount of herbicide intercepted, meaning that 75% of the applied herbicide was intercepted by 360 g·m-2 of litter. The majority of the herbicide was not tightly bound and a 15 mm simulated rainfall event removed 75% to 79% of the herbicide. This indicates that at sites with surface litter, timely precipitation could be critical for herbicide efficacy; however, when burning was used to remove litter and was followed by herbicides with residual soil activity, downy brome control could be extended. Due to downy brome's relatively short seed viability in the soil, extending herbicide efficacy to several years could help to reduce the soil seed bank.
Publications
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals? Now that I am back in the US, I have several projects that are underway dealing with managment of aquatic and terrestrial invasive weed species. Three of this projects will be completed this reporting season. I plan to publish this research in appropriate journals and provide extension/outreach programing to various clientele groups and stakeholders.
Impacts
What was accomplished under these goals?
I was on sabbatic leave from 1/1/2013 to 12/15/2013. I traveled to Perth, WA to work with Dr. Stephen Powles at the University of Western Australia on various aspects of herbicide resistance in several weed species. With funding from the Brazilian government under the CAPES program I worked with Dr. Pedro Christoffoleti at ESALQ in Piracicaba, SP. In Brazil, I taught several shortcourses on herbicide modes of action and herbicide resistance mechanisms in key weed species in Brazil and the US.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Lindenbayer, R. B., S. J. Nissen, P. Westra, D. L. Shaner, and G. Brunk. 2013. Aminocyclopyrachlor absorption, translocation, and metabolism in field bindweed (Convolulus arvensis). Weed Sci. 61:63-67.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: Field bindweed (Convolulus arvensis) is an herbaceous perennial weed introduced from Eurasia. It is one of those weed species that seems to be equally adapted to irrigated, dryland and non-crop environments. It is extremely difficult to control because of its extensive, creeping root system and so far has resisted mechanical, chemical and biological control. DuPont is developing a new herbicide, aminocyclopyrachlor, that has excellent activity against field bindweed at relative low use rates, for example rates as low as 30 g/ha. Many native grasses are tolerant to aminocyclopyrachlor so it appears that this new herbicide could be extremely useful for controlling field bindweed in non-crop settings where land managers want to establish native grasses. The objective of this project was to understand how field bindweed responds to aminocyclopyrachlor by tracing the movement and metabolism of aminocyclopyrachlor using radiolabeled herbicide. Compared to other herbicides, aminocyclopyrachlor had greater translocation to below ground plant parts (14% of applied activity) and no herbicide metabolism was detected 192 hours after treatment (HAT). Aminocyclopyrachlor translocated equally throughout the plant with the treated leaf, shoot and root all accumulating 13-14% of the applied radioactivity. The lack of herbicide metabolism 192 HAT could be one reason that field bindweed appears to be highly susceptible to this new herbicide. PARTICIPANTS: Dr. Brad Lindenmayer was a graduate student working on this new molecule. He is now a field biologist with Syngenta Corp. Dr. Dale Shaner is a plant physiologist with USDA-ARS Water Resources Group in Fort Collins and a well known weed scientist with a background in industry. Dr. Phil Westra is a professor of weed science at CSU. Mr. Galen Brunk is a research associate in the Weed Research Lab at CSU. He developed and validated all the analytical procedures used in this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Land managers have been looking for new management options to control field bindweed especially in areas where active restoration is planned. Aminocyclopyrachlor is a new herbicide that could be very useful to local, state, and federal land managers because it would provide long-term field bindweed control and still allow for native grass establishment. This research project provides some basic information about the behavior of this new molecule in a key weed species.
Publications
- Lindenmayer, R. B., S. J. Nissen, P. Westra, D. L. Shaner, and G. Brunk. 2012. Aminocyclopyrachlor absorption, translocation, and metabolism in field bindweed (Convolulus arvensis). Weed Sci. (in press).
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Eurasian watermilfoil (Myriophyllum spicatum) is an invasive aquatic macrophyte that infests lakes and some irrigation canals in Colorado. This invasive species can drastically impact recreation and ecosystem services normally provided by aquatic environments. Selective Eurasian watermilfoil control can be achieved with a number of herbicides like 2,4-D, triclopyr and endothall. Recently, a new herbicide, imazamox, was registered for aquatic uses, and its behavior in Eurasian watermilfoil was evaluated. This research is one of the more comprehensive studies evaluating herbicide absorption and metabolism in an aquatic species. Only about 1% of the imazamox in the water column was absorbed by the plant and absorption was directly related to the external concentration, indicating that movement into the plant was driven by diffusion. Imazamox metabolism was fairly rapid with only 20% of the absorbed imazamox remaining after 24 hours. As soon as the external concentration was reduced, imazamox moved from the plant to the water column to establish a new equilibrium concentration. Aquatic macrophytes, like Eurasian watermilfoil, have been studied as bio-accumulates of organic compounds for bio-remediation and as a risk to animals using these plants for food. This research represents one of the few studies examining the behavior of a highly water soluble herbicide in an invasive aquatic species. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: The target audiences for this research are local, state, and federal land managers that have responsibilities for management of invasive aquatic species. In addition, homeowner associations, golf courses, and irrigation companies will benefit from this research. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Managers of aquatic ecosystems are often dealing with invasive species like Eurasian watermilfoil. The results of this research provide these managers with critical information necessary to make appropriate decisions about using this new herbicide. Imazamox has attributes that make it a reasonable choice for managing this species. Applicators now have very detailed information about its behavior in the plant and the importance of managing water movement during treatment.
Publications
- Vassios, J.D., S.J. Nissen and G. Brunk. 2011. Imazamox absorption, desorption, and metabolism by Eurasian watermilfoil. J. Aquat. Plant Manage. 49:44-49.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: Ongoing research with Colorado's most common invasive perennial species, Canada thistle (Cirsium arvense), has built upon research conducted in 2009 with the herbicide aminopyralid and also focused on understanding the behavior of another new herbicide being developed by DuPont, aminocyclopyrachlor. Like aminopyralid, aminocyclopryachlor has excellent activity on Canada thistle and a number of other important invasive weed species. Research to understand the interactions of aminopyralid with soil was completed and results published in 2010. This work indicated that aminopyralid was not tightly bound to soil so most of the herbicide would be available for absorption by Canada thistle roots. This information helps to explain the wide range of effective application timings that we see with aminopyralid, but did raise some concerns about leaching potential. However, the leaching potential for aminopyralid appears to be less than with clopyralid, a herbicide previously considered the best choice for Canada thistle control. Aminocyclypyrachlor behaves much like aminopyralid when applied to Canada thistle. It has very limited translocation to Canada thistle roots, which would indicate that soil activity must be very important for control. Two new herbicides are available for Canada thistle control and both appear to rely heavily on root absorption for long-term control. There appears to be a balance between having enough herbicide available for root absorption and not having too much soil residue that might negatively impact restoration efforts. PARTICIPANTS: This project provided professional development for Dr. Bekir Bukun from Harran University, Sanlaurfa, Turkey. Dr. Bukun was a visiting scientist in my lab for 2 years. Dr. Dale Shaner is a collaborating scientist with the USDA-ARS in Fort Collins. This research also provided a training opportunity for Ph.D. student, Mr. R. Bradley Lindenmayer. TARGET AUDIENCES: The target audiences for this research are federal, state and local land managers and private landowners dealing with invasive weed species. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Federal, state and local land managers have limited budgets for invasive plant management and subsequent restoration programs. For many years, the conventional wisdom has been to spray perennial weeds like Canada thistle in the fall; however, this is also the best time to establish perennial grasses and forbs. This research indicates that perhaps paradigm shift is necessary to encourage land managers to consider using these new herbicides in the spring and seedling perennial grasses and forbs in the winter. Foliar absorption and subsequent translocation to Canada thistle roots is not the key for long-term control. Root absorption appears to be more important.
Publications
- Bukun B., R. B. Lindenmayer, S. J. Nissen, P. Westra, D. L. Shaner, and G. Brunk. 2010. Absorption and Translocation of Aminocyclopyrachlor and Aminocyclopyrachlor-Methyl Ester in Canada Thistle (Cirsium arvense). Weed Sci 58:96-102.
- Bukun B. , D. L. Shaner, S. J. Nissen, P. Westra, and G. Brunk. 2010. Comparison of the Interactions of Aminopyralid vs. Clopyralid with Soil. Weed Sci 58:473-477.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Canada thistle remains one of most common invasive perennial weed species in Colorado. It occurs in crop, non-crop, and riparian environments. A large regional project established that the new herbicide, aminopyralid, could provide long term Canada thistle control across many environments. A previous experiment concluded in 2007, included 10 environments across five states. While we knew that aminopyralid was effective, there was no information available about how aminopyralid behaved in Canada thistle. To better understand this herbicide's behavior in Canada thistle, we initiated a research project to compare absorption, translocation and metabolism of the new herbicide, aminopyralid, to a well-known and closely related herbicide, clopyralid. Experiments were conducted using radiolabeled aminopyralid and clopyralid that followed the herbicide's movement and metabolism over an eight-day time course. Clopyralid had significantly better absorption and translocation compared to aminopyralid and greater translocation to Canada thistle roots. Considering that aminopyralid provides better Canada thistle control at much lower field use rates than clopyralid, we have concluded that aminopyralid is either much more biologically active at the herbicide's target site or has better residual soil activity. We have initiated additional research to study the soil residual activity of aminopyralid and clopyralid. PARTICIPANTS: Dr. Bekir Bukun was a visiting scientist from Turkey that worked in my lab as part of a training program designed for career advancement in Turkey. Dr. Bukun is the equivalent of an associate professor in the Plant Protection Department at Harran University in Sanliurfa, Turkey. TARGET AUDIENCES: While this is a more basic research question, the results will be used to help local, state and federal land managers. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
With our understanding of how this herbicide behaves in plants we can begin to unravel the importance of herbicide application timing on long-term Canada thistle management. We now know that very little aminopyralid translocates to Canada thistle roots and yet this new herbicide has proven to provide consistent control. This suggests that there is considerably more leeway in application timing because foliar absorption does not appear to be critical factor. This finding suggests that land managers might have a much wider window of opportunity to seed restoration grasses than previously thought.
Publications
- Bukun, B., Gaines, T.A., Nissen, S.J., Westra, P., Brunk, G., Shaner, D.L., Sleugh, B.B. and Peterson, V.F. 2009. Aminopyralid and clopyralid absorption and translocation in Canada thistle (Cirsium arvense). Weed Sci. 57:10-15.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Canada thistle continues to be a serious weed problem in Colorado and many western states. It is an aggressive perennial that is adapted to both crop and non-crop environments. Canada thistle control in riparian areas has been difficult because many herbicides have ground water advisories that exclude application near surface water and in areas with shallow water tables. In the past year, two new herbicides have been registered that provide excellent Canada thistle control and have no ground water or surface water restrictions. Aminopyralid (Dow Agrosciences) and aminocyclopyrachlor (DuPont) could provide the opportunities for public and private land managers to control Canada thistle (especially in riparian areas), while establishing native plant communities that could resist re-invasion. The sensitivity of eight warm-season and seven cool-season native grasses to pre-emergence and post-emergence applications of these new herbicides was evaluated under field conditions. Aminopyralid and aminocyclopyrachlor were applied in June and September, 2007, followed by grass establishment in February, 2008. Once grasses emerged herbicide applications were made to seedling and fully tillered grasses. Both herbicides allowed for excellent grass establishment if the herbicides were applied in June 2007 or to fully tillered grasses in summer 2008. The other application timings cause significant injury and reduced grass establishment. These data indicate that shifting herbicide applications to the spring rather than the standard fall timing, will significantly enhance the establishment of native grass communities in Canada thistle infested areas. A vigorous native plant community that can provide wildlife habitat will be more resistant to re-invasion by Canada thistle and should provide the basis for sustainable weed management. PARTICIPANTS: Dr. Phil Westra, Colorado State University; Dr. Dale Shaner, USDA-ARS, Ft. Collins; Dr. George Beck, Colorado State University; Dr. Ken Lair, formally with Bureau of Reclamation TARGET AUDIENCES: city, county, state and federal land managers; NRCS districts; private consultants; county weed control supervisors; weed management cooperatives PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Public and private land managers need integrated programs that can provide long-term solutions to invasive weed problems. This research project was designed to provide information about herbicide rates, application timings and the response of native grass species so that a city, county and state land managers could design weed management programs with the greatest potential for success. In this case, success means that weed infestations are replaced by competitive, native grass communities and that the cost of making this transition is keep to a minimum by making minor changes in management techniques, i.e., spring vs fall herbicide applications.
Publications
- No publications reported this period
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Drought conditions have resulted in reduced recharge of many wildlife and recreational areas around Colorado. Cattails (Typha latifolia L.) and rushes (Juncus spp.) previously dominated these plant communities when water was more abundant; however, these plant communities have been replaced by invasive species like Canada thistle (Cirsium arvense (L.) Scop). Managing Canada thistle in these locations has been very problematic because most herbicides that could reduce these weed populations are restricted to upland sites with deeper water tables. Many land managers have resorted to mowing these sites just before flowering as their primary weed control strategy. A new reduced risk herbicide, aminopyralid (Dow Agrosciences), can be used in these environments, but there was no information on long-term Canada thistle control. A five state research protocol was established to evaluate aminopyralid rate and application timing (spring vs fall) and to compare efficacy to other
recommended treatments. Results from Colorado, Nebraska, North Dakota, South Dakota, and Wyoming were analyzed. Canada thistle control with aminopyralid was not significantly affected by herbicide rate or application timing and control was greater than 90% across locations. Control was also comparable to other commonly used herbicides. A number of additional studies have been established to evaluate aminopyralid in restoration programs designed to establish native or improved grass communities that will resist re-invasion by Canada thistle.
PARTICIPANTS: Dr. Scott Nissen, Professor, BSPM; Dr. Phil Westra, Professor, BSPM; Dr. George Beck, Professor, BSPM
TARGET AUDIENCES: Federal, state, county land managers and small acreage land owners
PROJECT MODIFICATIONS: none to report
Impacts
Canada thistle is the most ubiquitous invasive perennial in Colorado. It is one of the few major weed species that is equally adapted to agricultural and non-crop sites. In non-crop, riparian environments Canada thistle is almost impossible to control because effective herbicides were not available and other non-chemical strategies (mowing, burning, etc) do not reduce stem densities. Now land managers and small acreage land owners have the information necessary to use this new management option in the most cost effective manner with a research based understanding of the what to expect in terms of Canada thistle management.
Publications
- Enloe, S.F, R. G. Lym, R. Wilson, P. Westra, S. Nissen, G. Beck, M. Moechnig, V. Peterson, R. A. Masters, and M. Halstvedt. 2007. Canada thistle (Cirsium arvense ) control with aminopyralid in range, pasture and noncrop areas. Weed Tech. 21:890-894
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Progress 01/01/06 to 12/31/06
Outputs
Recreation and irrigation are important uses of Colorado's limited aquatic resources. These uses are threatened by the spread and rapid growth of both native and exotic submersed aquatic plants. The invasive, Eurasian watermilfoil (Myriophyllum specatum), currently infests 33 states including Colorado and negatively impacts recreation and the efficiency of water delivery systems ie., irrigation and drainage canals. In Colorado, Eurasian watermilfoil has spread from a single location in Boulder County to at least 10 other locations mainly along the Front Range. The native, sago pondweed (Potamogeton pectinatus L.), is a problem weed of rivers, irrigation and drainage canals throughout temperate and subtropical parts of the world. Sago pondweed is a recurring problem in irrigation canals along the Front Range and the eastern plains of Colorado. Once water temperatures reach 60F sago pondweed growth increases rapidly forcing irrigation districts to dredge canals with
backhoes in order to maintain water flow. Field and greenhouse research projects were established to evaluate the efficacy of imazamox for Eurasian watermilfoil and sago pondweed control. Imazamox is an imidazolinone herbicide registered for a number of terrestrial uses and currently under investigation as a potential new herbicide for aquatic weed management. Working under an Experimental Use Permit from EPA, we used imazamox to treat three small lakes heavily infested with Eurasian watermilfoil and monitored weed control and imazamox dissipation from mid May to August. The imazamox treatments significantly reduced Eurasian watermilfoil growth, keeping these lakes completely open for the summer. The imazamox concentration in these lakes decreased rapidly after application due to photodegradation. The half-life of imazamox in these aquatic ecosystems was approximate 4 days. Emerged sago pondweed was not susceptible to imazamox; however, imazamox did reduce sago pondweed biomass by 95%
when shoots emerged through treated soil. This indicates that imazamox could be used to treat dry irrigation ditches in the fall or spring and provide sago pondweed control the following irrigation season.
Impacts
A safe and cost effective method to control Eurasian watermilfoil will increase the recreational use of affected lakes and ponds, while the ability to control sago pondweed in irrigation canals will increase the efficiency of water delivery for irrigation and augmentation. Imazamox appears to be effective at much lower use rates than products currently labeled for Eurasian watermilfoil control and controlling sago pondweed with pre-emergence fall or spring application could reduce or eliminate the need to use acrolein. Acrolein is a highly toxic compound that was used for chemical warfare in World War I. Very few people are qualified to apply acrolein in the west and acrolein applications are dangerous and costly.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Riparian wetlands in the arid and semiarid west have been seriously degraded by the invasion of tamarisk. In a relatively short period of time this shrubby tree has destroyed native wetlands in Arizona, Southern California, Colorado, New Mexico, Texas and has moved north into Montana. Tamarisk control and restoration of native communities are possible, but this process can be very expensive and can fail to achieve the desired management goal. Research to evaluate integrated control strategies and their impacts on restoration success has been initiated at three locations in Southern Colorado. We found the interception of aerial applied herbicide, imazapyr, was only about 60% resulting in significant amounts of herbicide reaching the soil. This can seriously impact the cost of control and the success of subsequent native community establishment. In addition, the mechanical removal of tamarisk without herbicide treatments resulted in significant tamarisk regrowth (which
we did anticipate) and the proliferation of another invasive species, downy brome (Bromus tectorum). The ease with which one invasive plant species replaces another in these disturbed areas is a serious issue that will need to be address in any management plan. Analysis of soil samples for herbicide residue suggests that since the initial application in fall of 2004, the amount of herbicide present in the soil has decreased by almost an order of magnitude. Greenhouse bioassays studies indicate that a number of important native species will still be affected by herbicide residues of this concentration. Of the species tested, alkali sacaton (Sporobolus airoides) appears to be one of the most sensitive, while western wheatgrass (Pascopyrum smithii) is much more tolerant.
Impacts
Land owners and land managers across the west now realize the enormous negative impact that tamarisk is having on riparian ecosystems. The main impact of this research will be to empower land managers and landowners to initiate tamarisk removal and restoration programs that 1) are adapted to infestation densities, 2) preserve and protect as much native flora as possible, and 3) incorporate complementary strategies (biological control, herbicides, fire, shredding, planting native species, etc) to reduce the need for highly disruptive and expensive tactics like root plowing and root raking. This research seeks to develop a database that provides land managers and landowners with information about probable outcomes of integrated pest management (IPM) strategies applied to various infestation types (high, medium and low density tamarisk) with varying levels of remnant native vegetation.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Herbicide resistant weed management continues to be a significant issue for potato, onion, sugar beet and dry bean producers. Selection pressure is high in crops like corn and wheat where there are many other options for alternative modes of action. Producers that rely on other crops for their incomes must deal with these resistant weeds using a limited number of herbicide modes of action. Until recently potato, dry bean and onion growers did not have new modes of action to help manage triazine and acetolactate synthase (ALS) resistant weed populations. Based on research results from this project potato, dry bean and onion growers will have new products with modes of action that were not available two or three years ago. Sulfentrazone now has a Section 3 label that includes applications to potatoes and dry beans for 2004 field season, while flumioxazon has a Section 3 label for potatoes and onions for the 2005 field season. Field research results from this project
have been used to support these new registrations and provide information to develop directions for use. This project has also supported the Colorado onion industry by providing data necessary to support a Section 18 label for fluroxypyr to control volunteer potatoes in dry bulb onions. Volunteer potatoes are not only highly competitive with the onion crop, but can also serve a source of late blight inoculum. This project has also provided data to support a Section 18 label for fomesafen to control ALS resistant common waterhemp, which appears to be moving into eastern Colorado from western Kansas.
Impacts
Sulfentrazone and flumioxazon will not only provide potato growers with a new mode of action for weed control and resistance management, but could potentially save as much as $14 per acre in weed control costs. This could save the potato industry in Colorado $1.1 million per year. The impacts to the dry bean industry are also significant because this new product should improve late season nightshade control and provide a strategy to help control ALS resistant common waterhemp with to separate modes of action. For onion growers with significant volunteer potato problems conventional control methods resulted in a yield loss of 20-40%. Incorporating fluroxypyr in a weed management program could reduce yield losses to as little as 8-10%. Fortunately, there are a limit number of acres where onions are planted after potatoes.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The current recommendation for herbicide resistant weed management is to rotate crops and herbicide modes of action. Until recently potato, dry bean and onion growers did not have many new modes of action to help reduce triazine and ALS resistant weed populations. Based on research results from this project potato, dry bean and onion growers will have new products with modes of action that were not available two or three years ago. Sulfentrazone now has a Section 3 label that includes applications to potatoes and dry beans. Field research results from this project have been used to support these new registrations. This project has also supported the Colorado onion industry by providing data necessary to support a Section 18 label request for fluroxypyr to control volunteer potatoes in dry bulb onions. Volunteer potatoes are not only highly competitive with the onion crop, but can also serve a source of late blight inoculum.
Impacts
For potato growers the impact of this new product is not just a new mode of action for weed control but a saving of as much as $14 per acre in weed control costs. This could save the potato industry in Colorado $1.1 million per year. The impacts to the dry bean industry are also significant because this new product should improve late season nightshade control. For onion growers with significant volunteer potato problems conventional control methods resulted in yield losses of 20-40%. Incorporating fluroxypyr in a weed management program could reduce yield losses to as little as 8-10%.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Evaluations of new herbicides for weed control in potatoes have identified two compounds that have selectivity for weed control in potatoes. Sulfentrazone and flumioxazin have activity on weed species important in potato production and provide a new management tool for herbicide resistant weed management. Based on research results from this project that evaluated potato variety and weed response over several years and in Colorado's two potato production regions, a Section 18 label for sulfentrazone was granted in 2002. Because EPA approval was so late only a limited number of acres were treated with sulfentrazone in 2002. Growers were pleased with the results and cost so we anticipate that more acres will be treated in 2003.
Impacts
The impact of this new pest management technology will be to significanly reduce the cost of broadleaf weed control for growers. Current weed control costs per acre are approximately $30. New technology identified by this project can reduce that cost to $16 per acre. The savings to the Colorado potato industry would be approximately $1.1 million per year. In addition, this new product provides a new herbicide mode of action that is not currently used in potato production, providing a new tool for management of herbicide resistant weeds.
Publications
- Wilson, D. E., S. J. Nissen, and A. Thompson. 2002. Potato variety and weed response to sulfentrazone and flumioxazin. Weed Tech. 16: 567-574.
- Coggon, D. F., S. J. Nissen, S. D. Miller, and R. G. Wilson. 2002. Flumioxazin as a component of weed management in dry beans. Proceeding Western Society of Weed Science 55:10.
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Progress 01/01/01 to 12/31/01
Outputs
Soil applied herbicides represent the mainstay of potato weed management. Yield and quality losses from weed competition force potato growers to aggressively control weeds in order to produce profitable yields. Weeds can also harbor insects that vector potato diseases and reduce harvest efficiency. Research efforts have focused on identifying newer herbicides that will provide different modes of action for control of herbicide resistant weeds and potentially have a lower risk for movement to ground water. Sulfentrazone and flumioxazin are newer herbicides that inhibit an enzyme involved in the early stages of chlorophyll production. These herbicides control a number of weed species important in potato production. Various nightshade species are very susceptible to these herbicides at low rates. Field research suggests that when applied as pre-emergence treatments there is sufficient crop safety for use in potatoes and that most commonly grown varieties are tolerant.
Broadleaf weed control has been excellent over a number of years, across environments, soil types and irrigation systems. Data from this research was used to move sulfentrazone and flumioxazin into the IR-4 process. Residue tolerances and subsequent Special Local Need registrations are anticipated in the next several years. This new mode of action will provide potato growers with a valuable tool for the management of herbicide resistant weeds.
Impacts
This research will provide potato growers with more options in the battle to control herbicide resistant weeds. The number of herbicide resistant weeds has increased significantly since 1975 and only one new product for weed control in potatoes has been introduced in the last 15 years.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
Weed control in onions continues to be a significant input cost for growers; and with limited options for weed management, hand weeding is still necessary. Research has focused on developing new weed control technologies to replace DCPA for pre-emergence weed control. Early season weed competition can significantly reduce onion yield and quality. Pendimethalin has shown promise as an inexpensive pre-emergence herbicide for onions. Data generated by this research project has established rates and timing of pendimethalin applications that provide good to excellent early season weed control with acceptable crop tolerance. Pendimethalin provides good to excellent kochia control but has limited nightshade activity. Post-emergence nightshade and kochia control has been difficult with current technology. Weed control evaluations and onion variety response to fluroxypyr continue in support of a fluroxypyr IR-4 project. Ethofumesate has been evaluated for several years and is
currently moving through IR-4 to establish a tolerance for dry bulb onions.
Impacts
Data generated by this research was used to establish a delayed pre-emergence use for pendimethalin in dry bulb onions. This provided onion growers with an inexpensive way to control important weeds like kochia, lambsquarters and pigweed during stand establishment. This is the most critical period for weed management in onions.
Publications
- Coggon, D. and S. J. Nissen. 2000. EPTC incorporation methods: effects of varying time and quantities of water. Proceedings of Western Society of Weed Science 53:59.
- Nissen, S. J. and M. Bartolo. 2000. Pendimethalin and ethofumesate as DCPA replacements in dry bulb onions. Proceedings of Western Society of Weed Science 53:60
- Kazarian, D., S. J. Nissen, and A. Thompson. 2000. Sulfentrazone and flumioxazin for broadleaf control in potatoes. Proceedings of Western Society of Weed Science 53:76
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Progress 01/01/99 to 12/31/99
Outputs
The effects of weed competition on crop yield and quality impact net income for producers. Crops like potatoes and onions are marketed for quality as much as yield. Field experiments were conducted to evaluate management options that would limit the effects of weed competition on these crops. The loss of DCPA for pre-emergence weed control in onions has significantly limited the producer's ability to economical control the variety of weeds commonly found in most production areas. Pendimethalin has been used for several years for post emergence weed control, but limited information is available on the suitability of pendimethalin as a pre-emergence replacement for DCPA. Six field experiments were conducted to further evaluate the potential for pendimethalin to be used as a pre-emergence herbicide in dry bulb onions. The six locations varied in soil and irrigation type. At all locations, pre-emergence applications of pendimethalin provided weed control superior to DCPA,
with yields equal to, are greater than a handweeded check plot. EPTC is a commonly used for weed management in potatoes and is often applied by chemigation in major production areas of Colorado. Chemigation is an efficient method of application; however, continuing research has provided insights into the potential environmental fate of EPTC during and after chemigation. Soil moisture conditions at the time of application have a significant impact on the secondary volatility of EPTC. When EPTC is applied to soil with even moderate soil moisture, significantly amounts of the herbicide can be lost due to secondary volatility. Depending on soil moisture levels, EPTC losses can range from 30 to 60% within one hour of application. Chemigation or broadcast applications of EPTC to a dry soil surface greatly reduces the risk of volatility.
Impacts
Pendimethalin appears to have sufficient crop safety for pre-emergence applications to dry bulb onions and would provide an economical alternative to DCPA, with reduced risk of surface or ground water contamination. The environmental responsible use of EPTC requires that factors affecting herbicide performance be understood and communicated to producers. This research has identified a number of key factors that producers can control to improve the efficiency of EPTC use.
Publications
- Kazarian, D., Miller, P., Nissen, S.J., and Westra P. 1999. Dry edible bean response to shoot and foliar applications of dimethenamid, BAS656 and metolachlor. Proceedings Western Society of Weed Science p. 23.
- Coggan, D., Brunk, G., and Nissen, S.J. 1999. Effect of soil moisture on EPTC volatility. Proceedings Western Society of Weed Science p. 10.
- Nissen, S.J., Brunk, G., and Thompson S. 1999. Improving the efficiency of EPTC use in potato production. Proceedings Western Society of Weed Science p. 113.
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Progress 01/01/98 to 12/31/98
Outputs
Field evaluations of candidate herbicides to replace DCPA in onions indicate that ethosumasate and pendimethalin are potential replacement compounds; however, black and hairy nightshade still represent a significant problem in dry bulb onions. Weed control in transgenic sugarbeets suggests that glyphosate and glufosinate are generally superior to standard sugarbeet herbicides. Glyphosate provides better grass control than glufosinate, but effective weed management programs can be build around both compounds. The use of residual herbicides as PPI, PRE or lay-by treatments appears to reduce the number of glyphosate and glufosinate applications required. Eptc losses during chemigation are significant and primarily dependent on air temperature. Metolachlor and dimethenamid are not susceptible to losses during chemigation.
Impacts
(N/A)
Publications
- Nissen, S.J., G. R. Brunk, and G. Foster. 1998. Volatility losses of dimethenamid, metolachlor, and eptc during chemigation. WSWS Proceedings 51:12.
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Progress 01/01/97 to 12/31/97
Outputs
The voluntary removal of DCPA (Dacthal) from the market will significantly impact weed control options available for onion growers in Colorado. Dacthal was the only broad spectrum pre-emergence herbicide for use in onions and many other vegetable crops. Research efforts have been concentrated on identifying and supporting the registration of pest management products for pre-emergence weed control in onions. Field studies were conducted to evaluate a number of potential compounds for pre-emergence weed control. Ethofumesate has consistently provided good to excellent weed control with acceptable crop safety at rates up to 2 kg/ha. Weed control can be achieved with rates as low as 0.33 kg/ha. Under weed free conditions onion yields were not significantly different from ethofumesate treated plots compared to untreated control or DCPA treatments. Pesticide Clearance Requests were submitted for ethofumsate on dry bulb onions by most onion growing states in the west (this
effort was organized by Colorado). Data generated from this project have been used to support the need for ethofumesate as a pre-emergence and post-emergence compound for dry bulb onions. Ethofumesate use in dry bulb onions became a funded IR-4 project for 1998. Yellow nutsedge management has become a major concern for onion growers in Colorado and has been a second focus for research efforts. All major onion growing areas in the state have significant yellow nutsedge problems and 100% yield losses can occur with heavy infestations. Intense competition results in very small bulbs that have no market value. Metolachlor has a tolerance established on dry bulb onions by IR-4. Research was conducted to provide data in support of a Special Local Need Registration 24C. Under normal growing conditions metolachlor treated plots produced yields similar to untreated controls; however, adverse weather conditions can result in some stand reduction and yield loss. Heavy rainfall combined with
below normal temperatures result in for injury symptoms. The weed control benefits appear to be much greater than the risk of herbicide injury.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 01/01/96 to 12/30/96
Outputs
In Colorado, dry bulb onions are produced on approximately 18,000 irrigated acres, with an average gross revenue of over $50 million per year. Onion growers would like to reduce their reliance on hand labor for post-emergence weed control. Several herbicides evaluated under weed free conditions appear to have acceptable crop tolerance for pre-emergence and post-emergence weed control. Pendimethalin applied pre-emergence and ethofumesate applied alone as a pre-emergence treatment and applied post-emergence in combination with bromoxynil appear to provide good to excellent weed control with no adverse effects on onion yield. Pendimethalin is currently labeled for post-emergence applications only in onions and ethofumesate is used primarily in sugar beets. Thiazopyr was also evaluated for pre-emergence weed control in onions and appears to have acceptable crop tolerance at rates of 0.25 and 0.375 lb ai/ac. Data was generated to support a Special Local Need 24C Label for
post-emergence use of metolachlor in onions. Metolachlor would be very useful for the yellow nutsedge management in onions. Field survey data indicates that yellow nutsedge is a significant problem in all the onion producing areas of Colorado.
Impacts
(N/A)
Publications
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