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Show 4 - HARRIED TIMES - SEPTEMBER 15, 1995 RUSSIAN KNAPWEED—A NEW INVADER IN CASTLE VALLEY This summer a new noxious weed has been discovered in the lower portions of Castle Valley. To date, patches have been found on the Carey property and along CV Drive near Amber Lane. Hopefully, control efforts by private individuals and the County Weed Board will be able to contain and eliminate these two infestations. Both sites involve areas where fill dirt was brought in from outside the Valley. The following information is from a brochure printed by the "Fri-County Knapweed Committee: ” “Knapweeds belong to an aggressive group of weeds now invading our desert ranges. There are at least five very troublesome species (diffuse and russian knapwwds have been identified in CV). “The best method of control is prevention of movement and growth of the weed. Recognition of the weeds will help greatly in preventing their movement throughout the ranges. “Movement of this weed is accomplished by animals and wheeled vehicles, particularly recreation vehicles, because they do not stay on the roads. Clean all weeds off your RV when you move from one area to another. “Burn the weeds, including seed heads, to eliminate them. Otherwise, leave them in the area that you found them. Before seed formation, cutting the root off [??] will also destroy the weed and prevent seed formation. “Biological controls have had some limited success. A seed head fly lays an ess in the seed head. The larva eats the seed as it completes its lifecycle. “Infestations of these weeds are serious business. They destroy crop production and rangeland and some can even cause illness or death in grazing animals [particularly horses]. Quick and effective control of these weeds is a priority, but it is only possible when there is documentation of infestations. Please watch for these weeds and report any sightings immediately to your local weed control department or extension service.” The extensive root system formed by this perennial makes it particularly difficult to kill. The Grand County weed control agent is Tim Higgs who can be reached via mobile phone 260—1197. The following information is from Weeds of Utah by Arthur Holmgren and Berniece Andersen: CENTAUREA REPENS L. Russian knapweed. Another scientific name formerly used was Centaurea picris Pall. Probably introduced from the Old World with alfalfa seed, Russian knapweed is now common in most of the Western States. In Utah, the weed has become abundant in many areas, growing in a variety of habitats, meadows, cultivated and grain fields, ditchbanks, roadsides, and waste places. Because of its aggressiveness, abundance, and diffi— culty to control, it has become one of the most serious of Utah’s weeds. The slender, extensive rhizomes may penetrate to a depth of more than 2 feet in good soils, making eradication difficult. Description. Russian knapweed is a perennial from extensive horizontal rhizomes. The stems become 2 to 3 feet tall. lts stem leaves are usually 1 to 2 inches long, oblong-lanceolate, and have entire or toothed margins. The purplish flowers are borne in heads less than one-half inch broad, which occur singly at the tips of the upper branches of the plant. The flowers are bisexual, hence all may produce seed. The achenes are less than $4 inch long and mottled gray or brown. Russian knapweed, Centurea repens: A, drawing showing plants arising from underground rootstock; B, head consisting of numerous flowers; C, seed in face view; D, seed in side view; E, pappus arm; F, bract of head. |