Evaluating Herbicide Combinations and Application Rates on Texas Pricklypear

Pricklypear ( Opuntia spp.) occurs on about 28% of rangelands (10.3 million ha) in Texas and coverage is expanding due to overgrazing and mechanical disturbance. Although a native species to Texas rangelands, pricklypear can become so dense that it outcompetes other native vegetation, suppresses forage production, inhibits biodiversity, and limits livestock movement within pastures. Picloram (Pc) and picloram + fluroxypyr (Pc + F) have been effective at managing pricklypear, however, a herbicide combining picloram, fluroxypyr, and aminopyralid (Pc + F + A) has been reported to increase speed of plant mortality and enhance overall efficacy. We examined varying individual plant treatment and ground broadcast application rates consisting of combinations of picloram, fluroxypyr, and aminopyralid compared to standard industry rates of picloram and picloram + fluroxypyr on overall pricklypear mortality using individual plant treatment and ground broadcast applications across 13 sites on Texas rangeland from 2016 to ​2018. Individual plant treatment Pc + F + A (1%) achieved the highest mortality rate of 98.0 ± 3.5% two years post-application, significantly outperforming Pc (1%) at 76.4 ± 19.3%, while including aminopyralid at lower rates (0.75% and 0.5%) yielded comparable control at 96.2 ± 8.2% and 89.6 ± 14.5%, respectively. Ground broadcast applications showed no significant differences in mortality between Pc + F + A (2 336 mL/ha), Pc (2 336 mL/ha), and Pc + F (4 672 mL/ha), ranging from 66.8 ± 21.3% to 78.1 ± 20.2%, though lower rates (8 oz/ac and 16 oz/ac) reduced control to 44–59% ± 25%. These findings highlight the efficacy of higher treatment rates for consistent pricklypear management, with some lower rates offering similar outcomes, providing flexible options for rangeland managers.