Progress 04/29/14 to 09/30/18
Outputs Target Audience:Agricultural educators, pesticide applicators, and other scientists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Several graduate students were involved in design, implementation, data collection and analysis of studies during this period. How have the results been disseminated to communities of interest?Reports have been given to sugarbeet grower cooperatives and presentations given at the Western Society of Weed Science and Weed Science Society of America. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts What was accomplished under these goals?
Field studies were conducted in Sheridan, Wyoming, Huntley, Montana, Scottsbluff, Nebraska, and Fort Collins, Colorado. A total of 5 herbicide programs were applied in a randomized complete block design with six replicates at all locations. Herbicide programs included a control treatment that included only glyphosate applied four times to maintain the plots weed-free without causing sugarbeet injury. All other treatments contained the same glyphosate rates and timings, with other herbicides added in for control of resistant weeds. The other four herbicide treatments were selected based on their expected control of Palmer amaranth or kochia. For each target weed, a herbicide program was chosen that we expected would provide maximum postemergence control, and included the combination of phenmedipham plus desmedipham. Since this postemergence combination is no longer registered by the EPA, we also included a treatment for each target weed that relied on residual products only. At the 10 to 12 true-leaf stage, the GR Palmer POST herbicide treatment caused the greatest root biomass reduction of 20 to 23% compared to the glyphosate weed-free control (Table 2). The GR Palmer residual treatment and the GR kochia POST treatments showed an intermediary response, reducing root biomass by 12 to 17%. The injury observed shortly after the herbicides were applied was similar to that observed at the end of the season. Sugarbeet yield was reduced by at least one conventional herbicide treatment at 3 out of 4 field sites, with Huntley, MT being the exception where all herbicide treatments provided similar yields (Table 3). When all sites were combined for analysis, the GR Palmer POST treatment reduced sucrose yield by 11%, but all other treatments were statistically similar to the glyphosate weed-free control treatment. When analyzed individually by location, the GR kochia POST treatment reduced yield significantly at Sheridan, and showed an intermediary response at Scottsbluff and Ft. Collins. The herbicide programs tested, even those that cause substantial sugarbeet injury, will not provide consistent control of glyphosate-resistant Palmer amaranth or kochia. Previous research has shown the GR kochia POST treatment will typically provide between 70 to 85% control of glyphosate-resistant kochia, and the GR kochia residual treatment is likely to provide only up to 75% control of kochia. We have much less data on GR Palmer amaranth control in sugarbeet, but our expectation is that both treatments will provide less than 80% control of glyphosate-resistant Palmer amaranth. Therefore, even after these herbicide treatments are applied to glyphosate-resistant weeds, a substantial number of these weeds will still probably survive in sugarbeet fields.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Kniss, A. R Long-term trends in the intensity and relative toxicity of herbicide use. Nat. Commun. 8, 14865 doi: 10.1038/ncomms14865 (2017).
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Progress 10/01/16 to 09/30/17
Outputs Target Audience:Workshops were conducted involving professional agronomists, crop advisors, and farmers. A paper was published targeting scientists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Graduate students and undergraduate students participated in field studies related to this project. How have the results been disseminated to communities of interest?Hands-on workshops, field day presentations, andpeer-reviewed publications. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts What was accomplished under these goals?
A) An analysis of herbicide toxicity was conducted to determine the impact of large-scale changes in herbicide use in the United States. These findings have been useful in determining the need to reduce herbicide reliance. B) Preliminary data on kochia germination suggests that crop rotation and stale seedbed approaches may be a viable tool for kochia management over the long-term. C) We have continued to screen various herbicide modes of action in sugarbeet to find alternatives to glyphosate for reduced tillage sugarbeet production.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Gaines TA, Barker AL, Patterson EL, Westra P, Westra EP, Wilson RG, et al. (2016) EPSPS Gene Copy Number and Whole-Plant Glyphosate Resistance Level in Kochia scoparia. PLoS ONE 11(12): e0168295. https://doi.org/10.1371/journal.pone.0168295
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Kniss AR, Savage SD, Jabbour R (2016) Commercial Crop Yields Reveal Strengths and Weaknesses for Organic Agriculture in the United States PLOS ONE https://doi.org/10.1371/journal.pone.0161673
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Kniss AR (2017) Long-term trends in the intensity and relative toxicity of herbicide use. Nature Communications. 14865 doi:10.1038/ncomms14865
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Progress 10/01/15 to 09/30/16
Outputs Target Audience:The target audience was primarily other agricultural scientists during this reporting period. 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?During this reporting period, a peer-reviewed journal article was published in an open access journal. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts What was accomplished under these goals?
Glyphosate resistant kochia has become an increasing problem in Wyoming and surrounding states. We quantified the relationship between whole-plant kochia response to glyphosate and the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene copy number for kochia accessions collected from Wyoming, Nebraska, Colorado, and Montana. Our results suggested thatglyphosate resistance levelcan be accurately diagnosed using a relatively rapid test forEPSPS gene copy number, and documented the distribution of this problem in the 4-state region.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Gaines TA, Barker AL, Patterson EL, Westra P, Westra EP, Wilson RG, Jha P, Kumar V, Kniss AR. (2016) EPSPS Gene Copy Number and Whole-Plant Glyphosate Resistance Level in Kochia scoparia. PLoS ONE 11(12): e0168295. doi:10.1371/journal.pone.0168295
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Progress 10/01/14 to 09/30/15
Outputs Target Audience:Farmers, agriculturalists, and the general public were reached through several outreach venues, including presentations, meetings, and web postings. 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?Many field days and general presentations on the topics of herbicides were held. Blog posts were also written and published at www.weedcontrolfreaks.com. What do you plan to do during the next reporting period to accomplish the goals?Continue with field based studies as outlined in the original proposal.
Impacts What was accomplished under these goals?
A survey of glyphosate resistant kochia was conducted over a four-state region. Data were used to develop an empirical model relating the resistance mechanism (gene amplification) to field-level resistance. This will help provide real-time management decisions in glyphosate-based cropping systems in the region.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Gustavo M. Sbatella, Andrew R. Kniss, Lori Howlett, Robert G. Wilson. Exploring the Potential of Clomazone for Weed Control in Sugarbeets. Proc. Western Soc. Weed Sci. 68:34-35
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2015
Citation:
Meeks, J., A.R. Kniss. Residual Corn Herbicide Effects on Fall Cover Crop Establishment. Proc. Western Soc. Weed Sci. 68:82.
- Type:
Journal Articles
Status:
Submitted
Year Published:
2016
Citation:
Gaines, T.A., A.L. Barker, E.L. Patterson, P. Westra, E.P. Westra, R.G. Wilson, and A.R. Kniss. Prediction of glyphosate resistance level based on EPSPS gene copy number in Kochia scoparia.
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Progress 04/29/14 to 09/30/14
Outputs Target Audience: Target audiences include farmers and ranchers in the region, weed scientists and agronomists, and the general public. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? Four graduate students and one undergraduate student have been trained in general field study design, maintenance and data analysis. How have the results been disseminated to communities of interest? The data and recommendations were presented at numerous sugarbeet grower meetings in 2014. Using conservative estimates, our data has demonstrated that by spending an additional $35 per acre in corn for kochia control, growers could save up to $66 per acre in the subsequent sugarbeet crop for a net economic gain of $31 per acre. What do you plan to do during the next reporting period to accomplish the goals? We are currently evaluating the mechanisms of competition as they relate to early season weed competition. These results will have direct application for management of weeds before planting, especially in limited tillage systems.
Impacts What was accomplished under these goals?
A series of proactive field studies were conducted in collaboration with researchers at the University of Nebraska to develop management strategies to minimize the economic impact of kochia in sugarbeet rotations. The best herbicide combination in the sugarbeet crop provided only 70 to 95% control of kochia depending on environmental conditions. This treatment will be quite expensive (compared with glyphosate alone), and is an indication of how the cost of weed control may increase once glyphosate-resistant kochia invades sugarbeet fields in our region. Because glyphosate-resistant kochia control will be difficult in sugarbeet, it is imperative that kochia be managed aggressively elsewhere in the rotation. Our research suggests that if corn precedes sugarbeet in the crop rotation, the density of kochia can be reduced significantly by using a corn herbicide program that includes both preemergence and postemergence herbicides that are effective on kochia. It will be very important to control any kochia plants that escape herbicide treatment in crops preceding sugarbeet, because kochia is a prolific seed producer, and each surviving plant can result in nearly 200 seedlings the following year. To emphasize this point, consider the following scenario based on the data obtained from these studies: If only 1 or 2 plants per 100 feet of row survive or escape herbicide application in corn, it is likely that corn yield will not be reduced. The grower may have little interest in spending the time or money to remove those plants, even though removing those plants at this early stage by hand would cost less than $10/acre. However, if those 1 or 2 plants are left to produce seed in the corn crop, our data indicate we could expect between 200 to 400 seedlings per 100 feet of row the following year in the sugarbeet crop. If those seedlings are glyphosate-resistant it is quite possible we would not realize it until it is too late to use any control practices other than hand weeding. It would then cost well over $300/A to handweed that sugarbeet field. But even if we use a herbicide program in sugarbeet to target glyphosate-resistant kochia, we will likely only get 70 to 90% control of those 200 to 400 kochia seedlings. Even after spending additional money on herbicides, we would still likely have to spend between $20 to $150 per acre on hand weeding. The following recommendations were developed based on the results of these field studies: (1) Target kochia as the primary weed in all crops grown in rotation with sugarbeet. Always manage kochia aggressively in the rotation. (2) Use non-glyphosate herbicides that are effective on kochia in each of the crops rotated with sugarbeet. If the preceding crop is corn, Verdict PRE followed by Roundup plus Status POST has shown excellent kochia control, and uses three different herbicide modes of action that are effective on kochia. (3) Have a near-zero tolerance for kochia escapes in the crop preceding sugarbeet in the rotation. Each dollar spent on an additional herbicide treatment or even hand-weeding in corn may result in many dollars saved on weed control in the sugarbeet crop. (4) If you suspect kochia will be a problem in your sugarbeet field, apply Nortron (or another ethofumesate product) PRE. Use at least 24 fluid ounces per acre on sandy soils, and increase the rate accordingly for heavier soils.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2014
Citation:
Claypool, D. A. and A.R. Kniss. 2014. Safety of Encapsulated Acetochlor to replanted Glyphosate-resistant Sugarbeet. Proc. Western Society of Weed Science. 67:101.
- Type:
Websites
Status:
Published
Year Published:
2014
Citation:
Kniss, A.R. 2014. Regulating herbicide resistance. [Web Log Post]. http://weedcontrolfreaks.com/2014/06/regulating-herbicide-resistance/ Posted 23-June-2014.
- Type:
Websites
Status:
Published
Year Published:
2014
Citation:
Kniss, A.R. 2014. Dear Dr. Oz: We don't spray feathers. [Web Log Post]. http://weedcontrolfreaks.com/2014/09/dear-dr-oz-we-dont-spray-feathers/ Posted 23-September-2014.
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