Managing yucca in pastures

May 17, 2013
by WLJ

Yucca is a native perennial plant throughout much of the central western states of the U.S., ranging from the Mississippi to California. Yuccas are hardy plants and survive drought, fire and livestock grazing. Plant density can be as high as 2,000 plants per acre and at high densities, yucca can severely reduce quality and quantity of forage for livestock and wildlife.

Yucca infestation can have negative impacts on wildlife as well as livestock. If there are only a few plants, they can provide protection, food and nesting habitat for birds and small mammals. But when yucca numbers are too high, deer, pronghorn and cattle will eat yucca fruit and flowers. Crude protein content of yucca is 3-5 percent and therefore poor quality, robbing cattle of valuable nutrients if they turn to this plant as forage.

Seasonal development of established yucca begins in May with flowering. The fruits yucca form ripen in July and seed disperses in September. New plants are established by seed or ramets. Ramets are parent plant clones via rhizomes. Usually yucca establishes a new plant via seed and then colonizes the area via ramets.

Yucca control can be accomplished mechanically, mowing or shredding, but since mowing has rhizomes, mowing must be repeated.

Two methods of herbicide delivery have been tested, broadcast and directed whorl spraying. Broadcast application of Roundup Ultra (6 qt) and Ally (0.75 oz.) works pretty well. Yucca control after 15 weeks was 65 percent of plants under these protocols. But, of course, it uses a non-selective herbicide and may harm some of the desirable plants. Directed spraying with Remedy is much more effective but more labor intensive. Directed whorl spraying was 100 percent effective even after 30 months.

Directed whorl spraying to control yucca is simple. The Remedy/diesel fuel mix is 15 percent and 85 percent, respectively. Use a 5500-X1 nozzle and spray directly into the whorl for two seconds. This nozzle and length of time will allow the herbicide mix to penetrate the whorl. When mixing the herbicide with diesel, add Remedy to the tank first and then diesel till the mix is 15 percent herbicide and 85 percent diesel. Remedy RTU (ready to use) is already mixed for use.

Yucca is difficult to control in rangeland without help from herbicides. Fire must reach a high temperature and last a long time to kill the plants and seeds. Mowing isn’t effective since yucca can be regenerated from underground rhizomes. In heavily yucca infested areas, re-vegetation of grass and forages may be necessary. — Robert Tigner, University of Nebraska-Lincoln Extension Educator