Control strategies for sericea lespedeza
Sericea lespedeza continues to be a major concern on rangeland, pasture, and some CRP acres in Kansas. This state-wide noxious weed infests nearly 500,000 acres in Kansas (Figure 1).
Figure 1. Distribution of sericea lespedeza in Kansas.
Identification is an important first step before initiating a control program. Sericea lespedeza is a perennial legume with trifoliate leaves. The leaves are club or wedged shaped (Figure 2.). Plants are usually about 3 feet tall, but can grow to several feet in height under ideal conditions. Plants will start to bloom in August with white to cream-colored flowers with a purple throat. Most seed production occurs in September.
Figure 2. Trifoliate, wedge-shaped leaflets of sericea lespedeza. Photo by Walt Fick, K-State Research and Extension.
Currently, sericea lespedeza is in a vegetative growth stage (Figure 3) and is rapidly growing. By the end of June plants will begin to branch and become woodier.
Figure 3. Vegetative growth stage of sericea lespedeza. Photo by Walt Fick, K-State Research and Extension
There are no known biological controls that can be effectively used on sericea lespedeza. However, grazing with goats can suppress sericea lespedeza stands and produce a saleable product. It takes 4 to 5 goats per acre (of sericea) to graze the plant heavily enough to eliminate seed production.
Frequent mowing will reduce sericea lespedeza, but is also damaging to plants that might be growing/competing with sericea. A single mowing in mid- to late-July will eventually reduce stands of sericea lespedeza to some extent. Sericea has not been eliminated, however, even after several years of mowing. A late-summer mowing will eliminate most seed production. Application of appropriate herbicides about 4-6 weeks after mowing will help reduce sericea lespedeza stands, but will also damage other forbs. Prescribed burning in April seems to stimulate seed germination and needs to be followed up with an herbicide application. Burning in August and early September nearly eliminates seed production.
Herbicides applied at the correct time and under favorable environmental conditions can significantly reduce sericea lespedeza. Remedy Ultra (triclopyr) and PastureGard HL (triclopyr + fluroxypyr) can provide effective control when applied during June and into early July when the sericea plants are in a vegetative growth stage. Broadcast applications of Remedy Ultra at 1 to 2 pints/acre and PastureGard HL at 0.75 to 1.5 pints/acre should be applied in spray volumes of 10 to 20 gallons/acre.
Products containing metsulfuron, such as Escort XP, Cimarron Plus, and Chaparral, are generally more effective in the late summer when sericea lespedeza is actively blooming. Recommended rates are 0.5 oz/acre of Escort XP, 0.625 oz/acre Cimarron Plus, and 2.5 to 3 oz/acre Chaparral. Use a non-ionic surfactant with all of these products.
For spot application, mix 0.5 fl oz PastureGard HL per gallon of water, use a 1% solution of Remedy Ultra in water, or 0.3 gram Escort XP per gallon of water. Aerial applications of these products should be done with a minimum spray volume of 3 gallons per acre. Higher volumes, e.g. 5 gallons per acre, will generally be more effective.
Sericea lespedeza is a state-wide noxious weed in Kansas and therefore needs to be controlled. Sericea lespedeza has a tremendous seed bank that helps reestablish stands.
Herbicide treatments will need to be repeated every 2 to 4 years to keep this invasive species in check. Initial treatments should reduce dense stands to the point where spot treatment can be used in future years. Left untreated, sericea lespedeza will dominate a site, greatly reducing forage production and species diversity.
Walt Fick, Rangeland Management Specialist