Extension Agent: Field sandbur control in pastures
By Sam Womble
After two years of drought followed by plentiful rains, field sandburs (grassburs) are thriving in many locations. Sandburs are classified as a grassy annual weed and can be a problem in bermudagrass pastures. They prefer dry sandy soils, but can be found growing in many different soil types. The information that follows looks at Prowl H20, Roundup WeatherMax and Pastora. The application rates and evaluation results were documented through work conducted at the Samuel Roberts Noble Foundation.
Prowl H20 is a product that is applied to bermudagrass when it is dormant before the sandbur emerge. Pre-emergents are generally put out in February. Most pre-emergents require a rainfall event within a couple weeks after application for good results. Prowl H20 was applied at 2.1 and 3.2 quarts per acre and rated at 63 and 70 percent control.
Roundup WeatherMax (glyphosate) is an option for sandbur control following the first hay cutting on bermudagrass. It's important to note that when using glyphosate you generally have a five- to seven-day window following hay harvest. Roundup WeatherMax was applied at a 6.5 and 11 ounce per acre rate. Sandbur control was rated at 100 percent for each rate. Discoloration and reduced plant height was observed 14 days following the application, but the bermudagrass recovered. When the plots were harvested, there was no yield difference between the Roundup WeatherMax plots and the control.
Pastora is a product that has garnered a lot of attention recently. Perhaps one of the best attributes of this product is that there are no grazing or haying restrictions, which afford producers lots of flexibility. Pastora is applied when sandburs are less than 1.5 inches tall and bermudagrass is less than 4 inches tall following initial green up or after a cutting for hay. In the study, Pastora was applied at 1 and 1.5 ounces per acre. Sandbur control was rated at 97 percent and 100 percent, respectively. Although some crop injury was observed post treatment, the bermudagrass recovered. At harvest 35 days after the treatments, no statistically significant yield differences were noted in comparison to the control.
In summary, the data showed that all treatments have application in dealing with field sandbur. Visual crop injury is to be expected, but symptoms decreased significantly after 30 days. Prowl H20 showed good results, but a rainfall event following application is necessary. Roundup WeatherMax looks to have some value in a haying enterprise while Pastora looks to provide good post emergent results. Keep in mind that controlling field sandbur is not necessarily a one-time job. Additional follow up treatments may be necessary. Always follow the label and abide by any hay harvesting or grazing restrictions. Herbicide applications should be part of an overall management plan that includes good fertility and other best management agronomic practices.
Sam Womble is a Victoria County extension agent - natural resources.