. -
<br />'r' >~
<br />rr ,
<br />~~+~~
<br />4
<br />~~~
<br />~t
<br />'f~:.. ; t~t.:.
<br />,:, j"~~....,
<br />.. • a ..
<br />y..,,
<br />6patket ~;x~fff
<br />`~- -
<br />l4e~nrlp~ hrtda
<br />Spotted knapweed germinates in spring or fall. Perennial
<br />plants resume growOr 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 warm areas. It occupies dry meadows, pastureland, stony
<br />hills, roadsides, and the sandy or gravelly tloodplains 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 knapweed can be managed similarly. They aze
<br /> readily controlled with herbicides. However; the weeds will reinvade unless
<br />Spotted knapweed inlesfafions are not cultural techniques are used.
<br />as severe rn Colorado as diffuse CLemical conro4 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 />mPtaN- Far example, spotted knapweed 0.67 to 1 pUA, Curtail (clopyralid + 2,4-D) at 4 to 6 pUA, or BanveU
<br />was first observed in Gallatin County,
<br />Montana, in ttie 1920s, but is now Vanquish/Clarity (dicamba) at 1 to 2 pUA control diffuse knapweed. Tank
<br />found in all Montana counties. Today, mixes of BanvelNanquish/Clarity plus 2,4-D at 1 pt + 2 pUA or BanveV
<br />over 4.7 miAion acres are ;Wrested. VanquishlClarity 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-mites
<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 /> aeeas 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 lb)
<br />Livestock (sheep, goats, cattle) wilt 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 are used.
<br />research completed by Cdorado State Cultural control If desirable grass competition is evident in diffuse
<br />University shoes that cattle grazing
<br />diffuse knapweed twice in spring
<br />or spotted knapweed stands, judicious herbicide application that does not
<br />decreased seed set by 50 percent arai rnJLLTe grasses may allow them to compete effectively with the weeds.
<br />tumbling o/f-site over winter by t5 Irrigation (where possible) may help stimulate grass competition in these
<br />percent. Catde were managed to cases. However, infested rangeland or pasttues often aze degraded, allowing
<br />achieve 5o percent usfizaGon of pasture knapweed invasion, and herbicides alone will not restore Ute land to a
<br />arrd ware allowed m graze at too fa productive state. Seeding suitable perennial grasses is necessary to prevent
<br />day intervals when diffuse knapweed weed reinvasion.
<br />was boning afro' about s m f2 inches Biological control Many insects are being evaluated for biological
<br />talt 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 />~Cororadosrateuniwrsi(yrooperative Several insects are available in Colorado, from the Colorado
<br />r=xtension weed speaatisr and professor. Department of Agriculture. The seedhead flies Utaphora ajjinis and U.
<br />plant pamorogy and weed silence.
<br />quadrijasciata have been released in many Front Range counties. These
<br />Issued in furtherance cf Cooperative insects cause plants to produce fewer viable seeds and abort terminal or
<br />Extension work, Ads of May 8 and June 39, lateral flbwe75.
<br />1974, in cooperation with the U.S.
<br />oeparlmemotneer.,,hore,MiianA.ftewart~,
<br />Root-feeding insects may have a more detrimental effect on knapweed
<br />Director oFCooperative Exension, Cobrado populations than seed-feeding ones. Larvae of the diffuse knapweed root beetle
<br />state unitersiry, Fort Cdl;ns, Colorado. (gphenoptera jugoslavica) feed in the roofs of diffuse knapweed. Larvae of the
<br />Cooperative Extension programs are
<br />available to allwithou[discrimination.No
<br />yellow-winged knapweed moth (Agapera zoegana) feed and the knapweed
<br />erMorsemant olproduds mentioned is root weevil (Cyphocleorrus achates) in the roots of both ]mapweed species.
<br />intended nor is txiticism implied of products
<br />trot merrdOrred.
<br />
|