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United States Department of Agriculture

Agricultural Research Service

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Location: Foreign Disease-weed Science Research

2010 Annual Report

1a. Objectives (from AD-416)
The objectives of this research are to: 1) demonstrate the ability of Canada thistle seedlings, systemically diseased with the rust fungus Puccinia punctiformis, to reduce thistle density and provide sustainable biological control, 2) implement successful biological control of Canada thistle on a relatively large scale, and 3) provide land managers with the techniques to mass produce systemically diseased seedlings, introduce them into thistle patches, and effectively manage the patches to optimize biological control with the rust fungus and expand areas under control.

1b. Approach (from AD-416)
Canada thistle seedlings systemically diseased with the rust fungus, P. punctiformis, will be produced in greenhouses in either Ft. Detrick (for use in Maryland) or at Pennsylvania State University (for use in Pennsylvania). Diseased seedlings will be produced using teliospores of the fungus collected from the state of intended use, and seedlings will be transplanted to healthy patches in April. Either 0, 2, 4, or 6 systemically diseased seedlings will be established per each patch with one inoculum level per patch. At each inoculum level, half the number of the patches will be mowed and the other half left un-mowed. Procedures for producing systemically diseased seedlings will be transferred to stakeholders. We plan on locating and using 96 Canada thistle patches in 12 field sites, with about half of the sites in Maryland and half in Pennsylvania. A minimum of ten healthy thistle patches will be used for each field site. Stakeholders in charge of sites will mow or arrange to mow half of the patches in these sites. Data from each patch will be collected each year in June - July. Dependent variables will be: healthy Canada thistle density, diseased shoot density, and patch diameter. Data collection will be done by student interns under the supervision of a graduate student at Pennsylvania State University.

3. Progress Report
Project objectives are to: mass-produce Canada thistle seedlings systemically diseased with Puccinia punctiformis; establish mass-produced systemically diseased seedlings within naturally occurring thistle patches; assess, over a period of four years, the effects of systemically diseased plants on: 1) total thistle density; 2) systemically diseased shoot density; 3) patch diameter; and 4) demonstrate to public and private land managers the effectiveness of establishing systemically diseased seedlings on Canada thistle control. Diseased seedlings produced by this method at FDWSRU and Penn State University were planted into field sites in Maryland and Pennsylvania, respectively, during April and May, 2009. Disease progress is being assessed annually by students and technical support staff. In patches with established systemic disease, the density of healthy thistle plants has declined significantly while the density of systemically diseased plants has increased significantly. Results from these field sites and from laboratory tests have also led to a more complete understanding of the disease cycle of the rust fungus, and it is now possible to establish systemic disease through direct inoculation of Canada thistle plants with teliospores. This inoculation approach is more effective than establishing diseased seedlings in thistle patches and should lead to routine establishment of the disease in thistle patches. Inoculations with teliospores are planned for the fall of 2010 in farmers’ fields. Numerous meetings have been held with Penn State collaborators and with personnel from NRCS, state departments of agriculture, and state highway administrations to locate and manage these field sites.

4. Accomplishments

Last Modified: 06/24/2017
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