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Response of the Western Prairie Fringed Orchid to Herbicides and Biological Control Agents For Leafy Spurge Control

 Rod Lym

Question 1. What major problem or issue is being resolved and how are you resolving it?

Recovery of a leafy spurge infested habitat that sustains the western prairie fringed orchid (Platanthera praeclara Sheviak and Bowles). The orchid is a federally listed threatened plant species in the United States. The objectives of this research are to develop a herbicide treatment that controls leafy spurge while sustaining the western prairie fringed orchid populations and communities. Ideally a herbicide will control leafy spurge, allow the orchid to establish, and have minimum effect on other native species. Once the leafy spurge population is reduced biological control agents will be introduced to maintain leafy spurge control.

Question 2. How serious is the problem? Why does it matter?

Once widespread throughout the tallgrass prairie, the western prairie fringed orchid populations are now limited to isolated prairie remnants. According to the U.S. Fish and Wildlife Service there are approximately 40 populations of the orchid remaining. The three largest known populations of the orchid occur in Minnesota and North Dakota in the United States and southern Manitoba in Canada, with one of the largest occurring in the Sheyenne National Grassland of North Dakota. Areas in the grassland that presently support the orchid are impacted by leafy spurge which infests over 20% of the grassland and continues to expand. The continued spread of leafy spurge in the grassland is a major reason for loss of habitat for the orchid.

Question 3. How does it relate to the National Program(s) and National Program Component(s)?

The TEAM Leafy Spurge project is a part of the USDA/ARS Area-Wide Management Program. It is a component of Crop and Commodity Pest Biology, Control, and Quarantine (304). TEAM Leafy Spurge complements efforts to develop new and improved pest control technologies and assess component technologies for integrated pest management (IPM)systems.

Question 4. What was your most significant accomplishment this past year?

The objectives of this research are to develop a herbicide treatment that controls leafy spurge while sustaining the western prairie fringed orchid populations and communities. Unfortunately the location of our orchid/herbicide work established in 1998 was flooded from mid-September 1999 until July 2000 and had to be abandoned. A new location was selected in July 2000 and 95 orchids were marked and are ready for herbicide treatment in late-September 2000 in southeastern, ND. Our goals include the evaluation of an annual herbicide treatment on the orchid population (both regrowth and seed viability), demonstrating leafy spurge control and orchid recovery on a large scale (going from plots to several acres), and evaluation of the interaction of biocontrol agents, the western prairie fringed orchid, and herbicides.

Question 5. Describe your major accomplishments over the life of the project, including their predicted or actual impact.

Previously we had found that a fall herbicide treatment applied over the orchid does not adversely affect orchid growth the following season and in fact there was a tendency for more orchids to be found in treated compared to untreated plots. Treatments evaluated included imazapic (Plateau), quinclorac (Paramount), and a combination of glyphosate plus 2,4-D (Landmaster), and an untreated control.

Orchids regrew in an average of 66% of the plots treated with herbicides compared to 50% remaining in the untreated control plots. Numerous orchids germinated in many of the plots. The highest total number of orchids regrowing was 21 following the quinclorac treatment, with 16, 11 and 13 orchids found in the glyphosate plus 2,4-D, imazapic, and control treatments, respectively.

In addition to the orchid data, we conducted a seed-bank study to determine what plant species are most likely to regrow following a leafy spurge control program. Leafy spurge comprised 40% of all germinated seedlings followed by grasses (25%), and forbs (22%). These data indicate that once leafy spurge is controlled, the most likely plant to reinfest the area remains leafy spurge. Thus, an ongoing integrated control program will be needed, likely using both biological and chemical control methods.

Question 6. What do you expect to accomplish year by year, over the next three years?

Our goals include the evaluation of an annual herbicide treatment on the orchid population (both regrowth and seed viability), demonstrating leafy spurge control and orchid recovery on a large scale (going from plots to several acres), and evaluation of the interaction of biocontrol agents, the western prairie fringed orchid, and herbicides. These projects are ongoing in the Sheyenne National Grassland.

Question 7. 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?

We reported our results at the annual meeting of the Western Society of Weed Science which was well received and sparked a lot of interest as indicated by the numerous questions following the talk. News stories explaining the project and results to date were released by the NDSU Extension Service Communications Department for both print and broadcast media. In addition reporters from Minnesota Public Radio, Prairie Public Radio, and the Bismarck Tribune came to Lisbon to do stories on the orchid, leafy spurge, and our recovery efforts.

Question 8. List your most important publications in the popular press (no abstracts) and presentations to non-scientific organizations, and articles written about your work (NOTE: this does not replace your peer-reviewed publications which are listed below).

"NDSU research creates insight for managing federally protected plant". NDSU Ag Communications news release. 29 July 1999.

Attended the 16th Annual North Dakota Weed Control Association annual meeting and presented a paper entitled "Controlling Leafy Spurge with Minimal Damage to Endangered Species". Jamestown, ND. 11 to 13 Jan 2000. Attendance 155.

The MPR story (as mentioned in No. 7 above) received especially wide circulation as I have received favorable comments from people around the region including Minnesota, North Dakota, and Montana.

Question 9. Scientific publications

Sterling, J. J., R. G. Lym, and D. R. Kirby. 2000. Response of the prairie fringed orchid to herbicides for leafy spurge control. Res. Prog. Rep. West. Soc. Weed Sci. p. 207-209.

Sterling, J. J., D. R. Kirby, and R. G. Lym. 2000. Response of the western prairie fringed orchid to herbicides for leafy spurge. Proceed. West. Soc. Weed Sci. 53:98.

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