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Observation: Leafy spurge control in western prairie fringed orchid habitat


Kirby, Donald R.; Lym, Rodney G.; Sterling, John J.; Sieg, Carolyn Hull. 2003. Observation: Leafy spurge control in western prairie fringed orchid habitat. Journal of Range Management. 56(5): 466-473.

The western prairie fringed orchid (Platanthera praeclara Sheviak and Bowles) is a threatened species of the tallgrass prairie. Invasion by leafy spurge (Euphorbiaes esula L.) is a serious threat to western prairie fringed orchid habitat. The obiectives of this study were to develop a herbicide treatment to control leafy spurge while sustaining western prairie fringed orchid populations and to evaluate the soil seedbank composition of leafy spurge-infested sites to guide long-term management strategies. Quinclorac (3,7-dichloro-8-quinolinecarboxylic acid), imazapic ((±)-2-[4,5-dihydro-4-methyl-4-(l-methylethyl)-5-oxo-1H-imidazol- 2=yl]-5-methyl-3-pyridinecarboxylic acid), and glyphosate [N-(phosphonomethyl)glycine] plus 2,4-D (2,4-dichlorophenoxy acetic acid) were applied in the fall for 2 consecutive years, and changes in leafy spurge cover, density, yield, and herbaceous yield were assessed. In a separate study, quinclorac, imazapic, and glyphosate plus 2,4-D were each fall-applied to 12 western prairie fringed orchids and assessed for reoccurrence and density of orchids 1-year after treatment. Quinclorac and irnazapic, but not glyphosate plus 2,4-D, reduced leafy spurge cover, density, and yield without causing deleterious effects to associated native herbaceous cover and yields. Western prairie fringed orchid reoccurrence and density were unaffected by any herbicide 1 year after treatment. Soil cores were removed in spring and fall following the first year herbicide treatment, washed and placed in trays. Seedlings were allowed to germinate for 16 weeks in the greenhouse. Over 50 plant species were identified in the soil seedbank, of which approximately 60% were early sera1 species indicative of disturbance. Given the dominance of leafy spurge in the seed bank, a long-term management program to control this noxious species is warranted. Although these results are promising, longer-term studies need be conducted to ensure that repeated herbicide treatments do not harm the western prairie fringed orchid.

Keywords: invasive species, herbicides, range improvement, soil seedbank


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Title: RMRS Other Publications: Observation: Leafy spurge control in western prairie fringed orchid habitat
Electronic Publish Date: March 18, 2008
Last Update:
March 18, 2008

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