Sweet resin bush on the Santa Rita Experimental Range: An eradication effort

Abstract

Sweet resin bush (Euryops subcarnosus DC ssp. vulgaris B. Nord; or, Euryops multifidis (L. f.) DC.), a South African shrub introduced to Arizona in the 1930s, was discovered on the Santa Rita Experimental Range (SRER) in 1998. Due to the threat of spread of this invasive plant and its potential to cause adverse environmental and economic effects, and because it posed a threat to the Federally listed endangered Pima pineapple cactus (Coryphantha sheerii Muehlenph. L.D. Benson var. robustispina L.D. Benson), we initiated a project in early 1999 with the overall goal of eradicating about 154 acres of the shrub from SRER. Prior to initial treatments in 1999, permanent monitoring plots were randomly established within grazed and ungrazed areas that contained heavy, moderate, or no amounts of sweet resin bush. Plant cover (percent) and density (plants per 15m2) were sampled in January and February for 4 consecutive years (1999 to 2002). Sweet resin bush was hand grubbed in 1999, 2000, and 2001. Picloram (Tordon 22K) was spot sprayed via a backpack sprayer in February 1999 to soil areas where sweet resin bush had been grubbed. Initial eradication treatments in 1999 (mechanical + chemical) greatly reduced sweet resin bush species composition and density, and apparently released soil moisture and nutrients, allowing some native plants to re-establish in 2000. Sweet resin bush seedling density increased substantially in 2001; however, the combined effects of mechanical and herbicidal treatments along with periodic drought substantially reduced sweet resin bush density and canopy cover by 2002. No new seed production occurred for sweet resin bush on SRER during this 4-year study, and we detected no encroachment of sweet resin bush into uninfested control plots (grazed or ungrazed). Although this project greatly reduced sweet resin bush on SRER, total eradication of the shrub was not accomplished. Surveys and eradication efforts for sweet resin bush are planned on SRER for at least another 10 years.

Parent Publication

• Santa Rita Experimental Range: 100 years (1903 to 2003) of accomplishments and contributions; conference proceedings; 2003 October 30-November 1; Tucson, AZ

Citation

Howery, Larry D.; Munda, Bruce D.; Robinett, Dan G.; Buck, Harry H. 2003. Sweet resin bush on the Santa Rita Experimental Range: An eradication effort. In: McClaran, Mitchel P.; Ffolliott, Peter F.; Edminster, Carleton B., tech. coords. Santa Rita Experimental Range: 100 years (1903 to 2003) of accomplishments and contributions; conference proceedings; 2003 October 30-November 1; Tucson, AZ. Proc. RMRS-P-30. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 169-174.