Green Horizons

After our GH article on invasive plant species (Vol. 9, No. 2), a subscriber from Platte County wrote us about finding sericea lespedeza in their 40-acre field of native warm season grasses and asked if there was a way to kill the invasive plant without harming the native forbs.

Conventional management practices of grazing and prescribed burning have not been effective in preventing the spread of sericea. It is difficult to give grasses a competitive edge over sericea with season-long and rotational grazing because cattle will select grasses and leave the sericea plants. Grazing with meat goats has been used to reduce the production of seed. Stocking rates must be maintained at levels that will keep the sericea lespedeza grazed below a 3 to 4-inch height.

Spring burning removes the dead growth of sericea, but has no negative effect on established plants. Fire increases seed germination, thus promoting the establishment of new plants. However, burning can improve the effectiveness of herbicides if applied to regrowth the same year.

Mowing will reduce the vigor of sericea plants if cut close to the ground multiple times each year. Plants should be mowed each time they reach a height of 12 to 18 inches. The most damaging time to cut sericea is late in the growing season when the plants are trying to build root reserves for next year’s growth. Mowing will not kill sericea and may damage desirable grasses, depending on timing and frequency of cutting. In addition, a large sericea seed bank will remain in the soil, ready to germinate when conditions are suitable.

Very few herbicides for broadleaf weed control have provided good control of sericea lespedeza. Sericea has not been controlled with 2,4-D, and minimal kill has been achieved with a combination of picloram and 2,4-D (Tordon RTU^TM or Pathway ^TM) or dicamba and 2,4,D (Weedmaster^TM).

However, excellent control of sericea has been obtained with triclopyr (Garlon 3A^TM or Remedy^TM) and triclopyr + fluroxypyr (PastureGard^TM) applied in June to mid-July, and metsulfuron (Escort^TM or Cimarron^TM) applied in mid-July to late-September. While these herbicides can be used for weed control in the establishment and maintenance of native grasses, it is recommended that you first treat a small area to confirm the tolerance of your specific mix of native forbs before you treat the entire area. As always, read and follow label instructions and cautions.

A combination of the above control measures offers the most effective control of sericea lespedeza. Here is an example of an integrated program: Burn in late-spring (mid-May to mid-June) to remove new and dead sericea lespedeza growth, and to encourage germination of sericea seed. If grazing is an option, intensively graze areas until no later than mid-July. Three to five weeks after grazing ends apply a herbicide containing triclopyr or triclopyr+ fluroxypyr to the vegetative growth. During September, apply a herbicide containing metsulfuron to developing flowers and seeds of any plants that were missed by the earlier treatment. Exclude livestock from areas where sericea stands are producing seed to prevent further spread. If grazing is not an option, apply a herbicide containing triclopyr or triclopyr+ fluroxypyr to vegetative growth from June to mid-July, and/or herbicides containing metsulfuron to developing flowers from mid-July to late-September.