This has been a good year for grasslands in most of the eastern half of Kansas. But grasses and beneficial forbs aren´t the only plants that have benefited from the favorable conditions.
"Sericea lespedeza plants are starting to bloom across Kansas, with flowering likely to occur through much of September," said Kansas State University agronomist Walt Fick.
This is a good time to treat the invasive noxious weed with herbicides, said Fick, who is a rangeland management specialist with K-State Research and Extension. 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.
"At the bud and early flowering stage, sericea lespedeza can be controlled with Remedy Ultra (triclopyr) at 1.5 pints per acre," Fick said. "After sericea has reached the full-bloom stage until the first freeze, products containing metsulfuron are the herbicides of choice. Examples include Escort XP, Cimarron Plus, and others. The rate to use for any of these products is one-half ounce of metsulfuron per acre."
Metsulfuron can control sericea lespedeza even through seed fill, unless the plants are under drought stress, he said. However, the plants should be controlled before mid-seed fill.
"If the sericea has already formed viable seeds when it is treated with metsulfuron, the seeds can germinate the following year and spread the problem," the agronomist said.
Fick advised that grasslands with sericea lespedeza infestations should not be grazed or hayed after the sericea has gone to seed. This will only serve to spread the seed to other areas.
Next spring, areas with a sericea lespedeza infestation should be burned to encourage germination of sericea seed, remove new sericea growth and remove all dead plant material.
"After the burn, these areas should be intensively grazed until no later than mid-July. Four to six weeks after grazing ceases, any remaining sericea can be treated with Remedy Ultra," he said.
Fick said an alternative to the "burn-plus-graze-plus-herbicide" approach is to spray sericea lespedeza in June when the plants are in a vegetative growth stage with Remedy (1 to 1.5 pints per acre) or PastureGard (2 pints per acre).
More information is available at county and district K-State Research and Extension offices, or in the publication "Sericea Lespedeza: History, Characteristics, and Identification," The publication is alsK-State publication MF-2408: http://www.oznet.ksu.edu/library/crpsl2/mf2408.pdf.