Chemical control of yucca

Encroachment of Yucca sp. onto 130 million ha of native rangeland in the southwestern U.S. presents a critical situation to the range conservationist of today. Once mesquite (Prosopis sp.), juniper (Juniperus ashii and Juniperus pinchotii), and oak (Quercus sp.) are controlled, yucca often invades the cleared area. An evaluation of ten herbicides applied on two range sites (sandyland and mixedland range sites) indicates that the noxious species can be controlled with herbicides. Most foliarly applied herbicides, however, were ineffective when applied across all rates and dates. Dry herbicides, picloram (10% a.i. pellets), tebuthiuron (20% a.i. pellets), and dicamba (10% a.i. granules) gave the best results. Picloram (pellets) proved to be the most effective when applied in both range sites because the active ingredient is more effective at a lower concentration in the root zone. Both tebuthiuron and dicamba resulted in good control on the mixedland range site but were much less effective on the sandyland range site.