Russian Knapweed (Centaurea repens)

Description

Introduced from Asia. Perennial, reproducing by roots, rhizomes and seeds. Plants up to about 3 feet in height, from a particularly well-developed branching root system. Stems branched at base, striate, covered with downy-white hairs. Leaves of new shoots alternate, broadly lanceolate, a little toothed, somewhat whitish underneath. Lower leaves of plant rough; leaves of the flowering stems similar but much shorter. Flowers numerous, all tubular, rose to purple or blue, in composite heads which are flask-shaped, about 1-2 cm. long, solitary on the ends of leafy branches. Seeds are an ivory to light brown color, 2-3 mm. long, flattened, ovate shaped, longitudinal ridges, basal scar not oblique, with capillary pappus. Flowers, June - August. Seeds, August - September.

Prevention of Spread of Russian Knapweed

New infestations at Russian Knapweed may be reduced by planting weed free seed, feeding materials free of Russian Knapweed seed and cleaning equipment before leaving infested fields. Close attention should be placed on any feed or seed materials imported from the northern and northwestern states. Quick identification and destruction of Russian Knapweed plants is essential to prevent its spread.

Russian Knapweed Control Practices

Control of Russian Knapweed shall mean preventing production of viable seed and destroying the plant's ability to reproduce by vegetative means.

Cultural Control Practices

Cultural control methods have not been developed at this time.

Herbicides Approved for Controlling Russian Knapweed

The following herbicides may be used for cost-share with landowners. Other products labeled and registered for use on this noxious weed in Kansas may be used in accordance with label directions but are not available for cost-share. Be sure to follow all label directions and precautions. For additional information consult the current KSU publication of "A Chemical Weed Control for Field Crops, Pastures, Rangeland, and Non-cropland".

• 2,4-D Low Volatile Ester. Apply at the early bud stage. Follow label directions and precautions.

• Dicamba (Banvel, Clarity, Vanquish). Application shall be at the early bud stage in the spring and fall on pastures, rangeland and non-cropland. Follow label directions and precautions.

• Picloram (Tordon 22k). Restricted use pesticide. Follow label directions and precautions.

• Imazapic (Plateau). Apply during senescence in the fall. Follow label directions and precautions.

• Imazapic + Glyphosate (Journey). Apply during senescence in the fall. Follow label directions and precautions.