Open Space Advisory Board Agenda and Packet 2019 10 09

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Results: In the common mullein site, all treatments, had significantly reduced common mullein cover compared to the non -treated check 30 months after treatment (MAT) (Table 1, Figure 1). The Method + Esplanade treatment was omitted due to what appears to be an application error. The Tordon+Esplanade, Method/Telar + Esplanade and Tordon/Telar + Esplanade treatments were providing the best control 30 MAT, with an average of only 0.8% common mullein cover across all three treatments. Overall, treatments including Esplanade, except for Esplanade alone, had significant reductions in common mullein compared to treatments with Plateau (Table 1 and Figure 1). Treatments which included Esplanade also had 0% diffuse knapweed cover, while treatments which included Plateau did not reduce diffuse knapweed cover compared to the control (Table 1). Overall, treatments containing Esplanade had less weed cover compared to treatments without Esplanade (Figure 2). The Esplanade plots did have higher cover of Russian thistle and field bindweed compared to the other treatments. Downy brome seemed to outcompete Russian thistle and field bindweeds in treatment that lacked downy brome control (Figure 2). Evaluating perennial grass response at the Davidson Mesa common mullein site, there were significant increases in perennial grass biomass in the Tordon+Esplanade and Tordon/Telar+Esplanade compared to the non -treated check (Table 2 and Figure 3). Treatments without Esplanade did not have any increases in perennial grass. There were no significant differences in forb biomass, although forbs are inconsistently dispersed throughout the site. In the initial application season, all treatments except for Esplanade alone provided downy brome control, but by 30 MAT only treatments which included Esplanade continued to provide downy brome control (Table 1 and Figure 2). Downy brome, perennial grass and forb biomass were collected at the Davidson Mesa downy brome site. Initially, in the season following application (2017), Plateau was the only treatment to significantly control downy brome at both timings. In the assessment done 30 MAT, Esplanade treatments at 5 and 7 oz/A, along with the 3.5 oz/A rate at the late POST timing, had no downy brome present in the plots, while the Plateau treatments at both timings were no longer providing downy brome control (Figure 4). There were some increases in perennial grass and forb biomass among a few of the Esplanade treatments, especially treatments applied at the late POST timing (Figure 5). Downy brome, perennial grass, and forb cover was evaluated at the Aquarius Trailhead and Hillside sites in 2019. Diffuse knapweed cover was also evaluated at the Trailhead site. These sites were burned approximately 10 months after the early POST herbicide applications and 8 months after the late POST herbicide applications. Even with the burning, Esplanade at 5 and 7 oz/A were still providing excellent downy brome control, with cover averaging <1% among both treatments at the two sites (Tables 3 and 4, Figure 6). At the Aquarius Trailhead site, significant increases in perennial grass cover were observed in most of the treatments that were providing significant reductions in downy brome cover, while no increases in grass cover were observed in treatments that did not reduce downy brome cover (Table 3). Furthermore, all Esplanade treatments that provided significant reductions in downy brome cover also provided significant reductions in diffuse knapweed at the Trailhead site (Table 3). At the Aquarius Hillside site, there was less downy brome invasion, dense perennial grass and no forbs present. Perennial grass cover was not impacted at this site (Table 4). 18