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Russian Knapweed

Management

Cultural Management

Seeding and maintaining aggressive grasses such will help in competing with Russian knapweed and slow its spread. Proper fertilization, grazing, and supplemental irrigation of grasses are always effective cultural control methods.

Russian Knapweed flowerDue to the allelopathic properties of this weed, supplemental control methods, such as judicious use of herbicides, may be needed to give grasses a chance to compete. Additional herbicide treatments after grass establishment may be needed to keep Russian knapweed populations reduced to an acceptable level.

More complete information on grasses can be found on the Grass Seeding on the Eastern Front-Range of Colorado page or by contacting the Natural Resources Conservation Service.

Mechanical Management

Mowing and other mechanical methods can be employed every 14 to 21 days to prevent seed set and to stress the plants. Whether these efforts will reduce root mass and plant stand is unknown. As a creeping perennial, Russian knapweed is difficult to control by hand-pulling or grubbing. Cultivation is marginally effective on crop lands.

Biological Management

No effective biological control agents are known currently for this weed. Horses cannot be allowed to graze this knapweed as they can develop chewing disease. A root nematode (Subanguina picridis) Has provided poor control.

Herbicide Management

A number of herbicides are labeled for use on Russian knapweed. Those that have been effective when used independently or in combination with each other are: chlorosulfuron (Telar), picloram (Tordon), 2,4-D, glyphosate (Roundup, Rodeo), dicamba (Veteran 10G), and Curtail. Refer to table below for more information.

Herbicide
Labeled Site *
Rate (per acre)
Application Time
Tordon 22K All

1.0qt.

2qts. for spot treatment

Bud to early-flower stage and/or fall rosette.

Tordon 22K +

2,4-D Amine

All

1.0 pt. +

1 qt.

Bud to early-flower stage and/or fall rosette.
Curtail All 3 to 4 qts. Bud to early-flower stage. Fall is most effective.
Telar NC 1 to 3 oz. Perbloom to early-flower stage and/or 1 oz./ac. to fall rosettes.
Veteran 10g R & P, NC 1/2 to 1.0 lb. per 1000 s.f. To actively growing plants.
Transline & Redeem - - Contact weed department, online information will be posted soon.

* R & P = Range and Pasture; NC = noncrop; Crop = cropland; F = fallow; All = all of these sites.

Read the label to insure the herbicide is labeled for your application site.


 

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