Long-term Effects of Giant Smutgrass Control

B. Justesen, UF/IFAS Extension, Osceola County, Kissimmee, FL, J. Strickland, UF/IFAS Extension, Osceola County, Kissimmee, FL, and J. Yarborough, UF/IFAS Extension. Orange County, Orlando, FL.

Situation: Giant Smutgrass (Sporobolus jacquemontii) is a perennial bunch- type grass that produces over 45,000 seeds per plant per year. Weeds in pastures and rangelands cost ranchers and livestock owners in excess of $180 million annually in Florida. Chemical control for smutgrass is a great option for producers and is important to complete during the rainy months and is highly dependent on rainfall.

Methods: The smutgrass control trial was completed to determine the percent control of smutgrass using the herbicide hexazinone. The research trial was completed on a 2.0 hectare complete randomized block design with three replications. The two variables measured a cut and uncut and method of application. The blocks represented a cut wipe method with a 30% solution one direction, uncut wipe 30% solution one direction, cut spray 2.34 L/Ha, uncut spray 2.34 L/Ha, uncut control, and cut control. A visual percent control of plant density was completed by multiple agents before the trials were started. The trial began in August 2018. The visual percent control of plant density was completed by multiple agents at a year and half post treatment. The visual percent control for post treatment was to determine the long-term effects of chemical and mechanical control on smutgrass.

Results: Visual measurements were taken a year and half post herbicide application. The cut wipe method showed the largest percent control with a 55% reduction. Uncut wipe shows the second-best method with 32.5% reduction.

Conclusion: Long-term results indicate that management of the invasive bunch grass is possible with proper chemical and mechanical control methods. Interestingly, the wiper was far more effective than the traditional spray method.