Long-term results of tebuthiuron herbicide treatment on creosote bush ( Larrea tridentata ) in southeast Arizona, USA

Creosote bush (Larrea tridentata) is native to the southwestern United States and central Mexico. Experimental plots of creosote bush treated with tebuthiuron herbicide in southeast Arizona in the early 1980s were rediscovered in 2010. The response over the 30-year period was monitored, revealing creosote bush was effectively controlled by tebuthiuron; however, the anticipated recolonization by native grasses was not realized. Reducing the overall vegetative canopy cover of the site may leave the soil more susceptible to erosion, negatively affecting its hydrologic function. Land management strategies should more thoroughly consider shrub treatments in ecosystems receiving less than 254 mm of annual rainfall and inadequate seed source, such as this study site. Low and inconstant precipitation are typical of the American Southwest. This study demonstrates that, while brush management techniques are effective for long periods of time, the reduction of shrub cover does not directly stimulate recolonization of the site with native grasses.