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<br />Spotted knapweed germinates in spring or fall. Perennial
<br />plants resume growth in eazly spring and bolt at approximately the
<br />same time as diffuse knapweed. Flowering occurs through the
<br />summer into fall.
<br />Spotted knapweed is native to central Europe, where it is
<br />found in light, porous, fertile, well-drained and often calcareous
<br />soils in warn azeas. It occupies dry meadows, pastureland, stony
<br />hills, roadsides, and the sandy or gravelly floodplains of streams
<br />and rivers. Spotted knapweed tolerates dry conditions, similaz to
<br />diffuse knapweed, but survives in higher moisture areas as well
<br />(e.g., it thrives in the wetter conditions of the western Montana
<br />mountains). Spotted and diffuse knapweed infestations often occur
<br />together in Colorado.
<br /> Management
<br /> Diffuse and spotted Irnapweed can be managed similarly. They aze
<br /> readily controlled with herbicides. However, the weeds will reinvade unless
<br />Spotted knapweed infestations are no[ cultural techniques aze used.
<br />as severe in Colorado as diffuse Chemical control Research conducted at Colorado State University
<br />knapweed. However, this weed spreads indicates that Tordon 22K (picloram) at 1 to 2 pUA, Transline (clopyralid) at
<br />rapidly. For example, spotted knapweed 0.67 to 1
<br />11UA, Curtarl (clopyralid + 2,4-D) at 4 to 6 pUA, or Bam'eU
<br />was first observed in Gallatin County, Vanquish/Clarity (dicamba) at 1 to 2 pUA control diffuse knapweed. Tank
<br />Montana, in the r920s, but is now
<br />found in all Montana counties. Today, mixes of Bam'eUVanquish/Clarity plus 2,4-D at I pt + 2 pUA or BanveU
<br />over 4.7 minion acres are infested. Vanquish/Clarity plus Tordon 22K at 1 to 2 pt + 0.5 to 1 pUA or Tordon plus
<br /> 2,4-D at 0.75 pt + 2 pUA all control diffuse knapweed. These tank-mixes
<br /> may save money and reduce grass injury resulting from higher use rates of a
<br /> single herbicide.
<br /> Spotted knapweed and diffuse knapweed generally occupy the same
<br /> azeas in Colorado, so the same herbicide treatments can be applied. Weed
<br /> scientists at Montana State University indicate that 1 pUA of Tordon (0.25 ]b)
<br />Livestock (sheep; goats, came) will eat controls spotted knapweed for two to three yeazs, but the weed will reinvade
<br />diffuse and spotted knapweed. Recent the area unless other management techniques aze used.
<br />research completed by Caoredo State Cultural control If desirable grass competition is evident in diffuse
<br />University shows that came grazing or spotted knapweed stands, judicious herbicide application that does not
<br />diffuse knapweed twice in spring
<br />decreased seed set by 50 percent and
<br />injure grasses may allow them to compete effectively with the weeds.
<br />tumbling oft--site over winter by t5 Irrigation (where possible) may help stimulate grass competition in these
<br />percent Came were managed to cases. However, infested rangeland or pastures often are degraded, allowing
<br />achieve 50 percent utilization of pasdrre knapweed invasion, and herbicides alone will not restore the land to a
<br />and were allowed to graze at two ra productive state. Seeding suitable perennial grasses is necessary to prevent
<br />day intervals when diffuse knapweed weed reinvasion.
<br />was bating and about s to r2 inches Biological control. Many insects are being evaluated for biological
<br />hat control of diffuse and spotted knapweeds. Researchers at Montana State
<br /> University believe it will take a complex of insects (perhaps 12) to reduce
<br /> diffuse and spotted knapweed populations.
<br />'Coloratlo Slate University Cooperative Several insects are available in Colorado, from the Colorado
<br />Extension weed spedalist and professor. Department of Agriculture. The seedhead flies Urophora affrnis and U.
<br />plant pathology antl weed science.
<br />quadrifasciata have been released in many Front Range counties. These
<br />Issued in furtherance of Cooperative insects cause plants to produce fewer viable seeds and abort terminal or
<br />Extension work, Acts of May 8 and June 3n, lateral flOwerS.
<br />1914, in cooperation with the U.S.
<br />Department ofAgricukure, Milan A. Rewerts,
<br />ROOt-feeding InSeetS IDay have a more detrimeIltal effect On knapweed
<br />DirectorofCooperative E#ensicn, Colorado populations than seed-feeding ones. Larvae of the diffuse knapweed root beetle
<br />state university, Fort Conies, Coloredo. (Sphenoptera jugoslavica) feed in the roots of diffuse kuapweed. Larvae of the
<br />Cooperative Extension pregrems are
<br />available to allwithoutdiscdmination.No
<br />yellow-winged knapweed moth (Agapeta zoegana) feed and the knapweed
<br />eadocsemem afpreducts memioned is root weevil (Cyphocleonus achates) in the roots of both knapweed species.
<br />intended nor is criticism implied of products
<br />notmentioned.
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