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Transcript of Spotted Knapweed
- 1. Slide 1Spotted Knapweed (Centaurea stoebe ssp. micranthos)Susan FarringtonNatural History Biologist, Ozark RegionMissouri Department of ConservationSpotted knapweed was first introduced to North America from Eurasia as a contaminant in alfalfa seed inBritish Columbia in 1893. Its suspected that there were multiple accidental introductions, not just one.Slide 2Spotted knapweed is a short lived perennial which reproduces solely from seeds. It is called spotted because it has dark spots on the floral bracts.
2. Slide 3It typically forms a rosette in its first year, sending down a very taproot.Slide 4It flowers in subsequent years, typically flowering in June in our area. 3. Slide 5Its good to be able to recognize the seedheads, which retain the spotted bracts. These seedheads are visiblethroughout the winter.Slide 6The leaves are usually highly lobed and grey green in color, whitened with tiny hairs. They resemble a thistleleaf somewhat, but 4. Slide 7 Native field thistle (Cirsium discolor) Exotic bull thistle (Cirsium vulgare)there are no prickles on the leaves or stems. Here you see native field thistle on the left, with its whitenedundersides, and exotic bull thistle on the right, with its green undersides.Slide 8 Native Grey headed coneflower(Ratibida pinnata) Spotted knapweedIt also resembles native grey headed coneflower, but the coneflower leaves are a darker green and have fewerand larger lobes. 5. Slide 9Spotted knapweedGrey headed coneflowerConeflower also has spreading hairs on the stems and leaves, whereas knapweeds hairs are very tiny and fineand lay tightly against the leaf and stem.Slide 10Knapweed seeds remain viable in the seed bank 5-8 years, and germinate from spring through fall. Mowing itback does not prevent it from flowering or going to seed: I have seen it in a close-cropped lawn in upstate NewYork, blooming at 2 in height! 6. Slide 11Spotted knapweed is extremely adaptable, found at elevations up to and over 10,000 feet, and in areas thatreceive from 8 to 80 inches of rain annually.Slide 12It prefers well-drained, light-textured soils that receive summer rainfall. In MO, it likes roadcuts, gravel barsalong rivers and streams, pastures, glades and prairies. 7. Slide 13It can be easily spread when it is mowed after going to seed. It is also spread in gravel from infested gravel pits,or from ATV travel.Slide 14 Photos provided by MoDOTRoute 133 Pulaski CountyMay 2010This is Highway 133 in Pulaski County in May 2010. You can see knapweed showing up as blue-green patches amidst the fescue. 8. Slide 15Fall 2011Here it is in fall of 2011, and the patches have taken over nearly the entire highway interchange.Slide 16Although it typically starts in a disturbed area, it is very capable of moving into healthy pastures andundisturbed areas of high natural integrity. It exhibits allelopathic activity, suppressing the growth of otherplants. It does not compete well with vigorously growing grasses in moist areas, but in sunny dry areas, it canrapidly become a monoculture, and Ive seen it displace sericea lespedeza! 9. Slide 17Because it forms monocultures and crowds out other forage foods, this is a great threat to cattle producers.However, I had always thought knapweed was bad for cows, and have since learned it is actually reasonablygood forage. No one in their right mind would PLANT it in a pasture, but when faced with an infestation, cattleCAN be trained to eat it, and if they graze it BEFORE flowering, they can help keep it from going to seed.Slide 18Knapweed is highly branched above, and retains very little foliage below. In winter, this means there is verylittle vegetation on the ground except small rosettes. 10. Slide 19Spotted knapweed increases runoff and sediment (Lacey 1989) - harming aquatic wildlifeAs a result, spotted knapweed infested hillsides increased runoff 56% and sediment yield 192% overneighboring hillsides covered with native bunch grass (Lacey 1989). This can negatively affect our aquaticwildlife, including the Ozark hellbender, which has recently been listed as federally endangered.Slide 20Thru 1955In Missouri, knapweed was first collected in 1933 in Boone County and in Oregon County in 1955. 11. Slide 21 1960sTexas, Christian, McDonald and Holt Counties were added in the 1960s. Keep in mind the counties shown arethose where someone bothered to collect a specimen to submit to the MO Flora herbarium at the MOBotanical Garden.Slide 22 1970sIn the 70s, we added Stone, Carter, Reynolds, St. Francois, Franklin and St. Louis City to the list. 12. Slide 231980sIt spread more in the 80sSlide 241990sAnd the 90s 13. Slide 25 2000sAnd by the 2000s, it was established across much of southern Missouri, with additional populations scatteredareas around the state.Slide 26 Distribution in MOComparing the list of counties where it has been collected to the distribution listed on the EDD MappingSystem website, there are 5 more counties where it has been reported, but not collected for MBG. It ispossible that it is now in EVERY county in MO, but it hasnt been reported there yet. 14. Slide 27So what can we do to stop the onslaught? Small infestations of knapweed CAN be pulled, but it is difficult. Theplants have very deep tap roots, and it thrives in heavy clay and rocks, conditions that make it tough to pull.Make sure the ground is well moistened before you attempt pulling it. There is a persistent rumor thathandling it can cause cancer, but Ive never found anything to substantiate this claim. Gloves a good idea,though, as it may well be a skin irritant for some folks.Slide 28Spraying is far more practical. Currently, the best selective herbicide for it is aminopyralid, which is sold underthe brand name Milestone. It came out in 2005, and is selective mostly for forbs in the aster family. This is alarge family, unfortunately, so there are a number of forbs that are weakened or killed by the herbicide, but itis far more selective than previous herbicide recommendations for this noxious weed. 15. Slide 29 Milestone tolerance: Native forbCommon name Tolerance to Milestone: Allium stellatum Glade onion Tolerant Asclepias syriacaCommon milkweed Tolerant Echinacea purpurea Common name coneflower to Milestone: Native forb Allium stellatumPurple Glade onionToleranceTolerantTolerant Fragaria virginiana Common milkweed Asclepias syriacaWild strawberry TolerantTolerant Fragaria virginiana Wild strawberryTolerant Monarda fistulosa Monarda fistulosa Wild bergamot bergamotWildTolerantTolerant Verbena stricta VervainTolerant Verbena stricta Z. aptera GoldenVervain Zizia aurea and alexanders TolerantTolerant Aster laevis Zizia aurea and Z. aptera wild indigo alexanders tolerant Baptisia alba Smooth aster White GoldenModeratelyModerately tolerant Tolerant Aster laevis helianthoides GoldenSmooth aster Moderately tolerant Chrysopsis villosa Heliopsis aster Ox-eye sunflower Moderately tolerantModerately tolerant Baptisia alba Liatris asperaRough blazing starwild indigoWhite Moderately tolerant Moderately tolerant Silphium perfoliatumCup plantModerately tolerant Chrysopsis villosa Solidago giganteaGolden aster Moderately tolerant Late goldenrod Moderately tolerant Solidago missouriensis Missouri goldenrodModerately tolerant Heliopsis helianthoides prairie cloversunflower susceptible Dalea purpureaPurple Ox-eyeModeratelyModerately tolerant Desmodium canadense Showy tick trefoil Liatris asperacaptiata LespedezaRough blazingModerately susceptible star Round-headed bush clover Moderately susceptibleModerately tolerant Silphium perfoliatum CanadaCup plant Solidago canadensis Aster simplex goldenrodModerately susceptibleModerately tolerant White panicle asterSusceptible Solidago gigantea Dalea candidaLate goldenrod White prairie clover Susceptible Moderately tolerant Helianthus maximilliani Maximillian sunflowerSusceptible Solidago missouriensis Lobelia spicata Spiked Missouri goldenrodlobelia Susceptible Moderately tolerantOenothera biennis Common primroseSusceptibleRatibida pinnataGray headed coneflower SusceptibleRudbeckia hirta Black eyed Susan SusceptibleForbs that are tolerant or moderately tolerant of Milestone.Slide 30 Milestone tolerance:Native forb Common nameTolerance to Milestone:Dalea purpureaPurple prairie cloverModerately susceptibleNative forb Common nameTolerance to Milestone:Desmodium canadenseonionAllium stellatumGlade Showy tick trefoil TolerantModerately susceptibleAsclepias syriaca Common milkweedTolerantLespedeza captitataWild strawberryFragaria virginiana Round-headed bush clover TolerantModerately susceptibleMonarda fistulosa Wild bergamotTolerantSolidago canadensisVerbena stricta VervainCanada goldenrod Tolerant Moderately susceptibleAster simplex Z. aptera Golden alexanders panicle asterZizia aurea and WhiteTolerantSusceptibleAster laevisSmooth aster Moderately tolerantDalea candidaBaptisia alba White wildWhite prairie clover indigoModerately tolerant SusceptibleChrysopsis villosaGolden aster Moderately tolerantHelianthus maximilliani sunflowerHeliopsis helianthoides Ox-eyeMaximillianModerately tolerantsunflowerSusceptibleLiatris asperaRough blazing star Moderately tolerantLobelia spicataSilphium perfoliatumCup plant Spiked lobelia Moderately tolerant SusceptibleOenothera biennis Late goldenrodSolidago giganteaCommon primrose tolerantSolidago missouriensis Missouri goldenrod Moderately Moderately tolerant SusceptibleRatibida pinnata Purple prairie cloverDalea purpureaGray headed coneflower Moderately susceptibleSusceptibleDesmodium canadense Showy tick trefoil Moderately susceptibleRudbeckia captiataLespedeza hirta Round-headed bush eyed Susan susceptibleBlack clover ModeratelySusceptibleSolidago canadensis Canada goldenrod Moderately susceptibleAster simplex White panicle asterSusceptibleDalea candida White prairie clover SusceptibleHelianthus maximilliani Maximillian sunflowerSusceptibleLobelia spicata Spiked lobelia SusceptibleOenothera b