Response of Yucca to Fire, Herbicide, and Mechanical Treatments

Abstract

Response of individual yucca (Yucca glauca) plants to fire, herbicide, and mechanical treatments, applied singularly and in combination, was evaluated during two consecutive growing seasons. Plant tops were removed by burning plants with a propane burner or shredding to a 6 inch stubble height. Tebuthiuron [N-(5(1,I-dimethylethyl) -I,3,4-thiadiazol-2-yl)-N,N'dimethylurea] was applied at rates of 1 and 2 Ib a.i.lac and a 1:1 mixture of picloram (4-amino-3,5,6-trichloropicolinic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) was applied to yucca foliage at 2 lb/ac. Greatest plant mortality occurred when herbicides were applied alone, 67%, or when tebuthiuron at 2 Ib/ac was applied following burning or shredding, 73 and 93%, respectively. In contrast, burning and shredding alone caused yucca mortalities of only 13and 33%, respectively. Burned yucca, regardless of herbicide treatment, produced an average of 1.3 new shoots/plant compared to 0.3 shoots produced by unburned plants. Across all treatments, yucca weight declined 85% during the study period.