Progress 09/10/05 to 09/09/10
Outputs
Progress Report Objectives (from AD-416) To develop microbial herbicides to control important agricultural and invasive weeds and ecologically based weed management strategies for sustainable and organic production systems. Approach (from AD-416) A world collection of Pseudomonas syringae pv. tagetis will be screened for biological activity on Cirsium arvense to select the most efficacious strain. Molecular techniques will be used to enhance the biological activity of selected microbial biological control agents. The role of tagetitoxin in the biological activity of P. syringae pv. tagetis will be determined. A combination of descriptive research to define the impact of long-term cropping systems and component research to identify superior crop cultivars and cover crop management systems will be used to improve weed management systems. The resources of three long-term cropping systems experiments will be used to explore the influence of conventional and organic cropping systems on weed population dynamics. The influence of cover crop residue decomposition and its interactions with soil properties and seed depth on weed seedling recruitment will be determined. Research has been conducted during the five years of this project to develop biological agents for the control of weeds with a focus on developing phytotoxin-producing bacteria. Experiments were initiated to identify the regulatory mechanisms involved in the production of the phytotoxin, tagetitoxin, by P. syringae pv. tagetis, and to what extent these regulatory mechanisms could be altered to increase tagetitoxin production. Regulatory genes that up regulate and down regulate genes involved in virulence and pathogenicity in this organism were identified and characterized. This is the first study to identify genes required for tagetitoxin production and show that manipulation of biological mechanisms, such as membrane transport and regulatory systems for pathogenicity and virulence, may enhance the efficacy of this biological control agent. A polymerase chain reaction (PCR) protocol was developed to distinguish tagetitoxin-producing strains from non-toxigenic strains of P. syringae pv. tagetis. A surveyed of eastern Colorado and Wyoming and western Nebraska was conducted to determine the current distribution of the rust mite Aceria anthocoptes as a biological control for Canada thistle in mid-western states. The mite was found to be present throughout the region, although not present in all sites included in the survey. Based on plant density measurements at one of the locations, a gradual decline and ultimate disappearance of Canada thistle over an eight year period may have been attributed to the presence of the mite suggesting potential for use as a biological control agent. Research was also conducted to develop ecologically based management strategies for controlling weeds in sustainable and organic cropping systems. Initial research to identify competitive traits of soybean cultivars led to negative results and this approach was abandoned. However, research to establish that field crops had greater competitive ability against weeds in organic than in conventional cropping systems was completed through specific cooperative agreements with Penn State and Rodale Institute. Research for incorporating cover crops into reduced tillage organic weed management systems were pursued in collaboration with Penn State weed ecology scientists. We demonstrated that a two factor system including cover crop residue plus a high soybean population could synergistically suppress weeds compared to expected suppression based on either factor alone. Research under a USDA NEIPM grant demonstrated that success of a reduced tillage system with a hairy vetch cover crop for corn production was dependent on maintaining low weed populations as well as on the timing of planting relative to the pattern of weed emergence. Accomplishments 01 Demonstrated that a two factor system including cover crop residue plus high soybean population can synergistically suppress weeds compared to expected suppression based on either factor alone. Rye cover crop resid can serve as an initial agent of weed suppression while a closed soybean leaf canopy can effectively suppress weed establishment after leaf canop closure. By combining the early weed suppression of the mulch with the late weed suppression of the soybean canopy, the synergistic potential o this combination of tactics was demonstrated. We developed synergistic variations on a multiplicative model to describe weed responses to cerea rye mulch rate and soybean population density, individually, and to the combination of these tactics. This research shows one approach to achieving optimum weed management efficacy in high-residue, reduced- tillage cropping systems by employing multiple ecologically based tactic that may be marginally effective individually but can provide effective control when used in combination. 02 Factors influencing the efficacy of reduced-tillage organic corn production were identified. Reducing tillage in organic grain productio is a means of reducing the environmental, economic, and energetic costs grain production, however weed control is a major obstacle to achieving these goals. Supplemented weed communities seeded at three population levels at Penn State and ARS, Beltsville, were monitored to determine th affect of planting date and high-residue cultivation on weed establishme and subsequent crop yield. Corn yield declined with increasing weed abundance as a result of increasing weed seed populations in all site years. Delaying seeding reduced the degree of yield reduction by weeds but also included a yield penalty in some site years. High residue cultivation only consistently decreased weed biomass and improved corn yields in Maryland. Results suggest that the success of reduced tillage organic corn production is dependent on long-term reduction in the weed seedbank, but that delay in planting date and high residue cultivation c supplement weed control in selected situations.
Impacts
(N/A)
Publications
- Mirsky, S.B., Gallandt, E.R., Mortensen, D.A., Curran, W.S., Shumway, D.L. 2010. Reducing the germinable weed seedbank with soil disturbance and cover crops. Weed Research. 50:341-352.
- Ryan, M., Mortensen, D., Bastiaans, L., Teasdale, J.R., Mirsky, S.B., Curren, W., Seidel, R., Wilson, D.O., Hepperly, P.R. 2010. Elucidating the apparent maize tolerance to weed competition in long-term organically managed systems. Weed Research. 50(1):25-36.
- Ryan, M.R., Smith, R., Mirsky, S.B., Mortensen, D.A., Seidel, R. 2010. Management filters and species traits: Weed community assembly in long- term organic and conventional systems. Weed Science. 58(3):265-277.
- Ryan, M.R., Smith, R.G., Mortensen, D.A., Teasdale, J.R., Curran, W.S., Seidel, R., Shumway, D.L. 2009. Weed-crop competition relationships differ between organic and conventional cropping systems. Weed Research. 49(6) :572�580.
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) To develop microbial herbicides to control important agricultural and invasive weeds and ecologically based weed management strategies for sustainable and organic production systems. Approach (from AD-416) A world collection of Pseudomonas syringae pv. tagetis will be screened for biological activity on Cirsium arvense to select the most efficacious strain. Molecular techniques will be used to enhance the biological activity of selected microbial biological control agents. The role of tagetitoxin in the biological activity of P. syringae pv. tagetis will be determined. A combination of descriptive research to define the impact of long-term cropping systems and component research to identify superior crop cultivars and cover crop management systems will be used to improve weed management systems. The resources of three long-term cropping systems experiments will be used to explore the influence of conventional and organic cropping systems on weed population dynamics. The influence of cover crop residue decomposition and its interactions with soil properties and seed depth on weed seedling recruitment will be determined. Significant Activities that Support Special Target Populations An experiment was conducted in 2008 and 2009 to determine the role of the phytotoxin tagetitoxin in disease caused by Pseudomonas syringae pv. tagetis. The results of this experiment demonstrate that, in the absence of tagetitoxin, virulence of P. syringae pv. tagetis is greatly diminished, with the organism failing to induce stunting or impact seed yield, two major effects of this disease. Consequently, experiments were initiated to identify the regulatory mechanisms involved in the production of the phytotoxin and to what extent these regulatory mechanisms can be altered to increase tagetitoxin production by P. syringae pv. tagetis. An experiment was conducted in 2008 and 2009 to determine the importance of planting date, weed management, and weed seed density on reduced- tillage corn grown in a hairy vetch cover crop. Results of this experiment indicate that initial weed seedbank density strongly influences the success and required intensity of weed management and ensuing crop yield loss in reduced-tillage systems. While corn planting date did not significantly influence total weed biomass there was a shift toward a weed community structure where the dominant species were less competitive against corn. Another set of experiments were initiated to investigate various management practices for inhibiting the impact of weeds on soybeans grown in a rye cover crop.
Impacts
(N/A)
Publications
- Michels, Jr., G.J., Carney, V.A., Lydon, J., Ochoa, R., Renn, R.L. 2008. New records for Aceria anthocopes (Acari: Eriophyidae) occurring on Canada thistle in Colorado, Nebraska and Wyoming. Entomological News. 119:483-491.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) To develop microbial herbicides to control important agricultural and invasive weeds and ecologically based weed management strategies for sustainable and organic production systems. Approach (from AD-416) A world collection of Pseudomonas syringae pv. tagetis will be screened for biological activity on Cirsium arvense to select the most efficacious strain. Molecular techniques will be used to enhance the biological activity of selected microbial biological control agents. The role of tagetitoxin in the biological activity of P. syringae pv. tagetis will be determined. A combination of descriptive research to define the impact of long-term cropping systems and component research to identify superior crop cultivars and cover crop management systems will be used to improve weed management systems. The resources of three long-term cropping systems experiments will be used to explore the influence of conventional and organic cropping systems on weed population dynamics. The influence of cover crop residue decomposition and its interactions with soil properties and seed depth on weed seedling recruitment will be determined. Significant Activities that Support Special Target Populations Studies on the regulation of virulence factors of the weed pathogen Pseudomonas syringae pv. tagetis were conducted. Regulatory genes that up regulate and down regulate other genes involved in virulence and pathogenicity in this organism were identified and characterized. The research conducted is within the National Program Crop Protection and Quarantine (304), Research Component B. Weed Science, Component IX Biological Control of Weeds, A. Agent Discovery and Selection and Risk Assessment. A two-year field experiment was concluded on the persistence and identification of compounds released from rye cover crop residue that are allelopathic to annual weeds. After completion of laboratory analysis of allelopathic compounds, this project will be reported. A new field project has been initiated to determine the influence of weed population levels and community structure on weed management efficacy within several agronomic systems for managing cover crops in organic production of corn. This research was conducted within the National Program Crop Protection and Quarantine (304), Component X Weed Management Systems; Section A, Cultural and Mechanical Control, and Section B, Integrated Weed Management in Cropland. Technology Transfer Number of Web Sites managed: 1
Impacts
(N/A)
Publications
- Teasdale, J.R., Coffman, C.B., Mangum, R.A. 2007. Potential long-term benefits of selected no-tillage and organic cropping systems for grain production and soil improvement. Agronomy Journal. 99:1297-1305.
- Teasdale, J.R., Brandsaeter, L.O., Calegari, A., Neto, F.S. 2007. Chapter 4. cover crops and weed management. In: Upadhyaya, M.K., Blackshaw, R.E., editors. Non Chemical Weed Management Principles, Concepts and Technology. Wallingford, UK: CABI. p. 49-64.
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Progress 10/01/06 to 09/30/07
Outputs
Progress Report Objectives (from AD-416) To develop microbial herbicides to control important agricultural and invasive weeds and ecologically based weed management strategies for sustainable and organic production systems. Approach (from AD-416) A world collection of Pseudomonas syringae pv. tagetis will be screened for biological activity on Cirsium arvense to select the most efficacious strain. Molecular techniques will be used to enhance the biological activity of selected microbial biological control agents. The role of tagetitoxin in the biological activity of P. syringae pv. tagetis will be determined. A combination of descriptive research to define the impact of long-term cropping systems and component research to identify superior crop cultivars and cover crop management systems will be used to improve weed management systems. The resources of three long-term cropping systems experiments will be used to explore the influence of conventional and organic cropping systems on weed population dynamics. The influence of cover crop residue decomposition and its interactions with soil properties and seed depth on weed seedling recruitment will be determined. Significant Activities that Support Special Target Populations Vinegar application has been investigated as a method for weed management in organically managed edamame (Glycine max L.) and fall broccoli. Vinegar at 20% acetic acid concentration was applied to weeds within the crop row to achieve complete foliar coverage. Weeds between rows were controlled by cultivation. Edamame yields in treated rows were the same as yields from untreated plants. Broccoli plants treated with vinegar showed diminished leaf turger compared to the non-vinegar treated plants within 30 minutes of application. Plants treated with vinegar did not differ in size from the plants in the controls, although the lower leaves were chlorotic. Broccoli head counts were 8% higher than the unweeded controls and equivalent to the hand weeded treatment. However, total head weights and mean individual head weights were 25 and 30% lower for the vinegar treatments than for the hand weeded and unweeded controls, respectively. NP304 Component X, Weed Management Systems, Problem B, Integrated Weed Management in cropland. Accomplishments Organic Farming Improves Soil Fertility Compared to Conventional No- tillage Farming. Crop production without tillage is well-known for increasing soil organic carbon while organic farming is also known to increase soil carbon and improve soils in many of the same ways as no- tillage production. However, there is skepticism whether organic farming can improve soils as well as conventional no-tillage systems because of the requirement for tillage associated with many organic farming operations. A USDA-ARS research team at the Sustainable Agricultural Systems Lab conducted a nine-year comparison of selected minimum-tillage strategies for grain production of corn, soybean, and wheat in Beltsville, Maryland, from 1994 to 2002. After nine years, corn yields were 28% lower in the organic farming system than in the standard no-tillage system, partly due to poorer weed control in the organic systems. Despite the use of tillage, higher organic inputs into the organic system led to higher soil carbon and nitrogen concentration in the organic soils compared to those in all other systems. A uniformity trial was conducted from 2003 to 2005 with no-tillage corn grown on all plots. Yield of corn grown on plots with a nine-year history of organic management were 18% higher than those with a history of conventional no-tillage production, probably as a result of higher soil carbon and nitrogen. These results suggest that organic farming systems can provide greater long-term soil improvement than conventional no-tillage systems despite the use of tillage in organic systems, however, these benefits may not be realized because of difficulty controlling weeds in organic systems. NP304 Component X. Weed Management Systems. Problem B. Integrated Weed Management in Cropland. Crops Grown in Organic Farming Systems Enhance Tolerance to Weed Competition over the Long-Term. Research at the long-term Rodale Institute Farming Systems Trial investigated the competitive relations between weeds and grain crops as part of a collaboration between Penn State, Rodale Institute, and ARS under sibling projects 1265-22000-164- 01S and 1265-22000-164-02S. An analysis of weed biomass data collected since the start of the experiment in 1981 showed that weed biomass variation was greatest in the two organically managed systems and was sensitive to environmental fluctuations in rainfall timing and amount. The legacy effect from increased weed biomass in poor weed control years was negligible and did not result in immediate increases in weed biomass in subsequent years. Unexpectedly, crop yields were not significantly different among conventional and organic systems despite weed biomass averaging six times higher in the two organic systems. Experiments that were conducted within the long-term cropping systems trial in 2005 and 2006 to quantify the effects of crop and soil management practices on corn and soybean tolerance to weed competition showed that soil mediated resource availability and relative crop growth rate likely contributed to increased corn tolerance to weed competition in the organic systems. These results suggest that long-term organic farming can result in enhanced crop tolerance to weed competition as a result of integrated processes that buffer crop fitness during years of less than ideal weed control. NP304 Component X. Weed Management Systems. Problem B. Integrated Weed Management in Cropland. Technology Transfer Number of Web Sites managed: 2 Number of Non-Peer Reviewed Presentations and Proceedings: 5 Number of Newspaper Articles,Presentations for NonScience Audiences: 7
Impacts
(N/A)
Publications
- Casale, J., Lydon, J. 2007. Apparent effects of glyphosate on alkaloid production in coca plants grown in colombia. Journal of Forensic Science. 52:573-578.
- Teasdale, J.R., Abdul Baki, A.A., Park, Y.B., Rosecrance, R.C. 2007. The potential for allelopathy during decomposition of hairy vetch residue. In: Fujii, Y., Hiradate, S., editors. Allelopathy: New Concepts and Methodology. Enfield, NH:Science Publishers. p. 211-225.
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter? This project addresses the general need for novel biologically based weed management strategies in two parts. Part A focuses on development of microbial biological control agents (NP 304 Component IX, Biological Control of Weeds), while Part B addresses the development of ecologically based weed management (NP 304 Component X, Weed Management Systems). Part A is designed to develop microbial herbicides to control important agricultural and invasive weeds, with an emphasis on the invasive perennial weed, Cirsium arvense (L.) Scop. (Canada thistle). A world collection of Pseudomanas syringae pv. tagetis will be screened for biological activity on several genotypes of C. arvense and for pathogenicity on a range of related non-host plants, plants typically found in areas where the
biological control would be used, and crop plants. Efforts will be undertaken to enhance the biological activity of selected strains using molecular techniques to introduce genes for phytotoxin production, such as phaseolotoxin, tabtoxin, and caronatine. Non-toxigenic and toxin regulator mutants of P. syringae pv. tagetis will be developed and their biological activity compared to the wild-type strain to determine the role of tagetitoxin in the disease process. The genetic characterization of Aceria anthocoptes, the Canada thistle rust mite, will be conducted. Based on genetic differences identified, a DNA- based technique will be used to determine the natural distribution and host specificity of A. anthocoptes. Part B identifies ecologically based weed management strategies for sustainable and organic production systems. A combination of descriptive research to define the impact of long-term cropping systems and component research to identify superior crop cultivars and cover
crop management systems will be used to determine improved weed management systems. The resources of three long-term cropping systems experiments will be used to explore the influence of conventional and organic cropping systems on weed population dynamics. This research will define weed population trajectories, community structure, and competitiveness over the 10 to 25 years these experiments have been in operation and will provide insight into the most effective systems and rotational phases for controlling weeds. Unique tall growing soybean germplasm that has been developed at Beltsville will provide an opportunity to test the role of the tall growth trait on the competitiveness of soybeans with weeds. Finally, the influence of cover crop residue decomposition and its interactions with soil properties and seed depth on weed seedling recruitment will be determined. This information will allow the design of improved cover crop and tillage management approaches that could permit
the development of viable reduced- tillage organic cropping systems, currently an elusive goal. 2. List by year the currently approved milestones (indicators of research progress) Year 1 (FY 2006) 1. Strains of P. syringae pv. tagetis will be genetically characterized. 2. P. syrinage pv. tagetis will be modified with self-replicating plasmids containing phytotoxin-production genes and phytotoxin production by the resulting transformants will be evaluated. 3. Identify genes involved in the production of tagetitoxin, a phytotoxin produced by the biological control agent P.syringae pv. tagetis. 4. Analysis of basic agronomic data from the long-term Demo site will be completed. 5. Evaluation of the weed suppressive ability of soybean germplasm will be completed. 6. Initiate experiments to determine residue and soil factors that influence the recruitment of weed seedlings. Year 2 (FY 2007) 1. The efficacy of various P.syringae pv. tagetis strains will be determined. 2.
Non-toxigenic mutants of P. syringae pv. tagetis will be developed/selected. 3. The genetic characterization of Aceria mites will be completed. 4. A PCR protocol to distinguish A. anthocoptes from other Aceria mites will be developed. 5. A decision will be made whether further study of soybean cultivars and/or traits is warranted. Year 3 (FY 2008) 1. The host range of the most efficacious strain of P. syringae pv. tagetis identified in studies from the previous year will be determined. 2. Studies on the epidemiology of P. syringae pv. tagetis in populations of Canada thistle will be conducted. 3. The natural host range of A. anthocoptes will be determined. 4. The efficacy of bacterial biological control agents of weeds modified with phytotoxin production genes will be evaluated. 5. The role of tagetitoxin in the biological activity of P. syringae pv. tagetis will be determined. 6. Analysis of weed seedbank population trajectories and community dynamics at the Demo site and
relationship to similar data at the long- term FSP and FST sites will be completed. Year 4 (FY 2009) 1. Studies on the epidemiology of P. syringae pv. tagetis in populations of Canada thistle will be conducted. 2. Complete experiments to determine residue and soil factors that influence the recruitment of weed seedlings. 4a List the single most significant research accomplishment during FY 2006. Genetic and chemical characterization of a new bacterial pathogen of Canada thistle. A bacterium, Pseudomonas syringae strain CT99, that causes symptoms in Canada thistle that are similar to those caused by Pseuemonas syringae pv. tagetis was shown to be genetically different from all available Pseudomonas syringae pv. tagetis strains. Preliminary analysis suggests, however, that the phytotoxin produced by CT99 is chemically similar to tagetitoxin, a RNA polymerase inhibitor only reported to be produced by P. syrinage pv. tagetis. This newly discovered pathogen of Canada thistle needs
further evaluation to determine its host range and efficacy as compared to P. syringae pv. tagetis or other P. syringae strains isolated from diseased Canada thistle. [Natonal Program 304, Component IX, Biological Control of Weeds, Problem A. Agent Discovery and Selection and Risk Assessment.] 4d Progress report. Under objective B2, six cultivars of soybeans that ranged in height from tall to medium, that ranged in early growth rate from fast to slow, and that ranged in leaf shape from thin to wide were assessed for ability to suppress weeds. The trial was conducted in two fields with planted weed populations within row to achieve uniform weed pressure across each field and between fields. Although soybean cultivars exhibited the range of traits described above, there was no difference between cultivars in weed suppression. There also were small or no differences in the degree of cultivar growth and yield response to weed pressure. Results of this research demonstrated that the
hypothesis for objective B2, that tall stature and fast early growth will improve soybean competitiveness against annual weeds, was false. Therefore, scarce resources will no longer be allocated to this objective but will be directed to objectives B1 and B3, instead. 5. Describe the major accomplishments to date and their predicted or actual impact. Synergistic enhancement of weed control with a cover crop-herbicide combination. During the past decade, researchers and farmers have been developing preventive systems for controlling weeds that minimize the use of interventions such as herbicides. Cover crops are an important tool for protecting soil, managing nutrients, and suppressing weeds in sustainable production systems, however, cover crop residue left on the surface of soil often provides incomplete or inconsistent weed control. This research explored the relationship between the amount of residue of the cover crop, hairy vetch, and the amount of the herbicide, metolachlor,
applied to the soil surface on weed control. A synergistic relationship was demonstrated, meaning that by combining amounts of residue and herbicide that were marginally effective when used alone, a high degree of weed control was achieved. These results could open a new area of research that would target combinations of cover crops and low levels of selected phytotoxins to maximize weed control with minimal environmental impact (Component X - Weed Management Systems, Problem B. Integrated Weed Management in Cropland). Allelopathy makes short-term contribution to weed suppression by cover crops. Residue of leguminous cover crops such as hairy vetch contributes to integrated weed management and provides nitrogen for subsequent crops. Research was conducted to determine the role that toxins released by decomposing residue play in suppressing weeds, a process known as allelopathy. Results showed that hairy vetch residue that was allowed to decompose in the field or that was subjected
to leaching in the laboratory was less suppressive of weed emergence and/or growth than was residue that was fresh. Results demonstrated that allelopathy contributes to weed suppression by the release of water-soluble phytotoxins from fresh hairy vetch residue for a relatively short time following cover crop kill until leaf tissue has decomposed (Component X - Weed Management Systems, Problem A. Cultural and Mechanical Control). 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The research results from the characterization of P. syringae strain CT99 should be available to other scientists in FY2007.
Impacts
(N/A)
Publications
- Teasdale, J.R., Pillai, P., Collins, R.T. 2006. Synergism between hairy vetch residue and low rates of metolachlor [abstract]. Weed Science Society of America Meeting Abstracts. 46:51.
- Teasdale, J.R., Abdul Baki, A.A., Park, Y.B., Rosecrance, R.C. 2006. The potential for allelopathy during decomposition of hairy vetch residue [abstract]. Proceedings of Northeastern Weed Science Society. 60:58.
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