Open Space Advisory Board Agenda and Packet 2019 10 09

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Section 1: Abstract Abstract: Invasive species management on non -crop and rangeland remains a constant challenge throughout many regions of the United States. While there are over 300 rangeland weeds, downy brome (Bromus tectorum L.), Dalmatian toadflax (Linaria dalmatica), musk thistle (Carduus nutans), common mullein (Verbascum thapsis), and diffuse knapweed (Centaurea diffusa) have emerged as some of the most invasive and problematic. Downy brome (Bromus tectorum L.) is a competitive winter annual grass that is considered one of the most problematic invasive species in rangeland. It has been estimated the western United States rangeland is infested with over 22 million hectares of downy brome. While glyphosate, imazapic, and rimsulfuron are the current industry standards for annual grass control, all of these restoration options provide inconsistent control or cause injury to desirable perennial species. The increasing spread of biennial species is a result of their adaptability, life cycle, and prolific seed production. Herbicides with both foliar and soil -residual activity (2,4-D, aminocyclopyrachlor, aminopyralid, chlorsulfuron, clopyralid, dicamba, fluroxypyr, metsulfuron, and picloram) are most commonly used, yet these control options lack residual seedling control resulting in rapid re -invasions. For this study, vegetative surveys were conducted after herbicide treatments were applied to evaluate control of weed species and release of desirable perennial grasses and forbs. All data was analyzed in ARM by analysis of variance to determine optimum treatments. First year results showed that treatments including Esplanade or Plateau plus Method or Tordon had significant reductions in common mullein cover, while Esplanade treatments also provided Russian thistle control. By the second year, treatments which included Esplanade provided superior common mullein control compared to most treatments which included Plateau. The combination of Esplanade plus Method and Telar provided excellent common mullein control while also increasing perennial grass biomass and not effecting native forb cover. In year one, Plateau was the only treatment to provide downy brome control. By year two, only treatments which contained Esplanade (5 or 7 oz/A) were providing downy brome control (near 100%). This research ultimately provides a new, long-term control option for controlling noxious weed species on City of Louisville Open Space properties including Aquarius and Davidson Mesa Open Space. Section 2: Introduction Objective: Objective 1: To demonstrate that indaziflam (EsplanadeTM, Bayer CropScience) can be used as a new chemical treatment for successfully restoring Open Space lands invaded by downy brome and other invasive weeds such as common mullein. Objective 2: To better understand which herbicides alone, and in combination, provide long-lasting invasive weed seedling control without injuring perennial species. Objective 3: To evaluate how desirable native grass, forb, and shrub species respond to herbicide treatments. Objective 4: Compare the efficacy of herbicide treatments using a prescribed burn management approach as compared to non -burned sites Hypothesis: 11