1a.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.

1b.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.

3.Progress Report
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.

4.Accomplishments
1. While several biological control agents have been developed and released to control Canada thistle (Cirsium arvense), this invasive species continues to be a major pest in temperate regions of the U.S. To assess the use of the rust mite Aceria anthocoptes as a biological control for Canada thistle in mid-western states, a survey was conducted in eastern Colorado and Wyoming and western Nebraska to determine its current distribution in these areas. 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. This study, which provides information on the current distribution of A. anthocoptes on Canada thistle, will be of value to biological control practitioners interested in controlling Canada thistle in agricultural and natural areas. NP 304, Research Component B. Weed Science, Biological Control of Weeds.

5.Significant Activities that Support Special Target Populations
None.

6.Technology Transfer

Number of Web Sites Managed	1
Number of Non-Peer Reviewed Presentations and Proceedings	3
Number of Newspaper Articles and Other Presentations for Non-Science Audiences	2

Review 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.