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Injection of Herbicides into Rhizomes of Knotweeds and Other Invasive Species
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Injection of Herbicides into Rhizomes of Knotweeds and Other Invasive Species


We ran trials on this method for a few years as did other organizations and individuals. Ultimately, we did not find its efficacy to outweigh the labor involved. Therefore, Green Shoots decided not to …

We ran trials on this method for a few years as did other organizations and individuals. Ultimately, we did not find its efficacy to outweigh the labor involved. Therefore, Green Shoots decided not to launch the product. We have however had real success with foliar applications using our Green Shoots Foam Herbicide Dispenser. John Lampe gave a presentation on that system at the 2014 Upper Midwest Invasive Species Conference:

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  • 1. Injection of Herbicides intoRhizomes of Knotweeds and Other Invasive Species Upper Midwest Invasive Species Conference October 29-31 La Crosse, Wisconsin John Lampe Green Shoots, LLC Saint Paul, Minnesota 1
  • 2. Knotweed – Why Control?• It is listed by the World Conservation Union as one of the worlds 100 worst invasive species.• This is not precise ranking but does show recognition of how problematic species is.
  • 3. Outline of Talk• Background on Knotweed• Current Chemical Control Methods• How Can Our Methods be Improved to: – Reduce quantity of herbicide used – Reduce off-target harm
  • 4. Common Species of Knotweed• Japanese knotweed (Polygonum cuspidatum)• Giant knotweed (Polygonum sachalinense)• Bohemian knotweed (Polygonum x bohemicum) – hybrid
  • 5. IdentificationGood source: Prather TS, Miller TW, RobinsSS, Knotweed shrubs: identification, biology, andmanagement, Pacific Northwest ExtensionPublication 2009
  • 6. Knotweed Colony
  • 7. Knotweed Leaves • Dark green leaves • Un-toothed • alternatePhoto Credit: Steve Manning, Invasive Plant Control,
  • 8. Knotweed Stems - Young
  • 9. Knotweed Stem - Dry • Hollow internodes • Septum separating • Up to 2 in. dia. Photo Credit: James H. Miller, USDA Forest Service,
  • 10. Knotweed RhizomeRhizome
  • 11. Knotweed Spreads by• Rhizome extension – up to 6 to 8 feet a year• Distribution of plant parts – Rhizome pieces – as small as 0.7 g (Brock 1992) – Node pieces• Seeds – not major source in WA. (Miller 2005)
  • 12. Knotweed Badness• Riparian areas especially vulnerable• Out-compete other plants => monoculture – Loss of trees – Changes in soil fertility – Erosion along streambeds and stream banks
  • 13. Knotweed Monoculture Photo Credit: Justin Knabe, Minnesota DOT
  • 14. Knotweed Rhizome Extension Photo Credit: Popplewell Associates, York, UK
  • 15. Knotweed Rhizome Extension
  • 16. Knotweed Rhizome Extension
  • 17. Non-Chemical Control• Not practical except with small infestations• Danger of vegetative spread• See King County, Best Management Practices (2008)
  • 18. Chemical Control Methods• Foliar• Stem injection• Cut stem
  • 19. Key Herbicides• Glyphosate – aquatic label• Triclopyr – aquatic label; only foliar• Imazapyr – aquatic label; only foliar
  • 20. Knotweed Rhizome Tough to Kill!Key Problem: older parts of rhizome and dormantbuds are weak sinks. (Bashtanova et al. 2009.)
  • 21. Knotweed Rhizome – Tough to Kill!
  • 22. Foliar• Advantages – Fastest application method – Decent control: 81%. (Miller 2005)• Disadvantages – Off-target harm: Avg. injury: 68%. (Miller 2005) – Hard to treat tall plants
  • 23. Stem Injection
  • 24. Stem Injection• Use hypodermic or special injector• Inject up to 5 ml into stem• Between 1st and 2nd node above ground
  • 25. Stem Injection• Advantages – Precision – No stem disposal – Efficacy; Avg control: 88% (Miller 2005)• Disadvantages – Time-consuming – Id of treated stems – Non-target injury: 26% (Miller 2005)
  • 26. Biggest Disadvantage of Stem Injection• Requires 5 ml of herbicide per aerial shoot – Equivalent to frill application on 10 to 15 inch woody stem. AquaMaster Label.• Aerial shoot density averages about 9 stems/m2. Brock 2007.• 45 ml of 54% a.i. glyphosate per square meter.• May explain 26% non-target injury found by Miller.
  • 27. Cut Stem• Cut stem 5 to 10 inches off ground• Immediately pour up to 3 ml into hollow of stem
  • 28. Pouring Herbicide into Cut Stem
  • 29. Cut Stem• Advantages – Low cost equipment – Control? (Miller did not test)• Disadvantages – Time-consuming – Disposal of green aerial shoots – Amount of herbicide used
  • 30. Stem Wipe• Inconsistent Results (Miller 2005)
  • 31. Follow-Up Applications• Washington State Dept Agriculture: – Data show “significant decrease in knotweed following six years of annual treatments. – However, knotweed is still present at each monitoring site.” (Statewide Knotweed Control Program; 2010 Progress Report)
  • 32. How Can Methods Be Improved?• Reduce repeat applications• Reduce quantity of herbicide used• Reduce off-target harm
  • 33. We Have BeenTrying Several Methods
  • 34. Rhizome Injection
  • 35. Rhizome and Roots
  • 36. Rhizome Injection Needle reaches to below-ground Internode
  • 37. Herbicide Used• AquaMaster – glyphosate; 54% a.i.• Dose at 2ml• Well below AquaMaster label rate for hollow stem injections: 5 ml
  • 38. Inserting Needle into Cut, Dead Stem
  • 39. Injecting into Rhizome through Cut Stem
  • 40. Inserting Needle into Bent Live Stem
  • 41. Results?
  • 42. Ongoing Rhizome Injections• Winter and early spring injections did not produce results• Late spring injections show promise• Currently doing tests – late summer and Fall
  • 43. Other New Methods Being Explored
  • 44. Cut, Bend, and . . .
  • 45. Treat with Foam Herbicide
  • 46. Munch, Bend, and . . .
  • 47. Treat with Foam
  • 48. Tromp, Wait, and . .
  • 49. Treat Regrowth with Foliar Applied
  • 50. Low Volume Foam Herbicide
  • 51. Bend and Immediately Treat . . .
  • 52. Stems and . . .
  • 53. Foliage
  • 54. Potential Advantages of Foliar Methods• Not treating tall plants – reduces off-target harm• Treating with Foam Herbicide – Improves adhesion – Reduces drift• Late season – should improve treatment success
  • 55. Rhizome Injection Methods• Less time consuming• Less herbicide• Injecting into rhizome – will this improve treatment success?
  • 56. Bent Stem Wiping Methods• Exposing vascular tissue• Foam herbicide sticks to stem• Uses a lot less herbicide
  • 57. Green ShootsJohn Lampe – contact:•• 651-245-4682 (cell)• Email or call for copy of presentation 58