Observation: Leafy spurge control in western prairie fringed orchid habitat

Abstract

The western prairie fringed orchid (Platanthera praeclara Sheviak and Bowles) is a threatened species of the tallgrass prairie. Invasion by leafy spurge (Euphorbia esula L.) is a serious threat to western prairie fringed orchid habitat. The objectives 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.-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 imazapic, 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 seral 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, longerterm studies need be conducted to ensure that repeated herbicide treatments do not harm the western prairie fringed orchid.

Rehabilitating Downy Brome (Bromus tectorum)–Invaded Shrublands Using Imazapic and Seeding with Native Shrubs

“…Imazapic suppressed invasive species without affecting native plant species in some studies (Davidson and Smith 2007;Kirby et al 2003), whereas others found imazapic negatively affected some native species (Baker et al 2009;Shinn and Thill 2004). If imazapic is used in the fall, it may be selective for actively growing plants with minimal harm to perennial plants (Davidson and Smith 2007;Vollmer and Vollmer 2008).…”