Late summer and early fall can be a good time to treat sericea lespedeza with herbicides, according to Walt Fick, K-State Research and Extension range management specialist.
This noxious weed is a problem on grazing lands in Kansas since it is unpalatable to cattle and competes with desirable grasses and forbs, Fick says.
Controlling sericea lespedeza has proven to be unusually difficult, but a combination of practices that include well-timed herbicide applications can be effective.
"Sericea can be difficult to control with grazing, mowing, or burning alone. Most often, a herbicide application will be necessary as part of an integrated management approach. Managers should be aware, however, that drought stress can greatly reduce the effectiveness of herbicides applied for sericea lespedeza control," Fick explains. "A good indicator of drought stress is the amount of flowering. Sericea will produce very few flowers when under drought stress."
If the sericea hasn't flowered yet, Remedy (triclopyr) at 1.5 pints/acre can give good control, Fick says. Remedy can be applied anytime from four to six weeks after grazing termination up until the pre-flowering stage of growth.
After sericea has flowered and up until the first freeze, metsulfuron (Escort, Ally, Cimarron, and other trade names) is the best herbicide to use, he says.
"Metsulfuron can control sericea even through seed fill, unless the plants are under drought stress. Managers should control the plants before mid-seed fill, however. If the sericea has already formed viable seeds when it is treated with the herbicide, the seeds can germinate the following year and spread the problem," the agronomist says.
Grasslands with sericea lespedeza infestations should not be grazed or hayed after the sericea has gone to seed. That could spread the seed to other areas, he says.
Control measures taken this fall need to be followed up for control to be most effective.
"Next spring, areas with a sericea infestation should be burned in the spring to encourage germination of sericea seed, to remove new sericea growth, and remove all dead growth. After the burn, these areas should be intensively grazed until no later than mid-July," Fick says. "Then, four to six weeks after grazing termination, any remaining sericea can be treated with Remedy (triclopyr) anytime up until flowering. An alternative to the burn-plus-graze-plus-herbicide approach is to spray sericea in June when the plants are in a vegetative growth stage with Remedy (1-1.5 pints/acre) or PastureGard (2 pints/acre)."
More information about sericea lespedeza is available on the K-State Research and Extension Web site: www.oznet.ksu.edu/sericea.