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 Upper Midwest Invasive Species Conference: http://www.slideshare.net/johnlampe/how-to-kill-i.

1. Subterranean Rhizome Injection of
Herbicides for Knotweeds and Other
Invasive Species
Midwest-Great Lakes Chapter, Society for Ecological Restoration
Fourth Annual Chapter Meeting
University of Michigan
John Lampe
Green Shoots, LLC
Saint Paul, Minnesota
May 5, 2012
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3. Knotweed – Why Control?
• It is listed by the World Conservation Union as
one of the world's 100 worst invasive species.
• This is not precise ranking but does show
recognition of how problematic species is.

4. Outline of Talk
• Knotweed Background
• Current Control Methods
• Rhizome Injection

6. Knotweed Background
Pioneer species in native habitat – for example,
Mt. Fuji

7. Common Species of Knotweed
• Japanese knotweed (Polygonum cuspidatum)
• Giant knotweed (Polygonum sachalinense)
• Bohemian knotweed (Polygonum x
bohemicum) – hybrid

8. Knotweed Colony
Photo Credit: Randy Westbrooks, U.S. Geological Survey. Bugwood.com

9. Knotweed Leaves
• Dark green leaves
• Un-toothed
• alternate
Photo Credit: Steve Manning, Invasive Plant Control, Bugwood.com

10. Knotweed Stem - Dry
• Hollow internodes
• Septum separating
• Up to 2 in. dia.
Photo Credit: James H. Miller, USDA Forest Service, Bugwood.com

11. Knotweed Stems - Young

12. Winter Dry Stems
Photo Credit: Justin Knabe, Minnesota DOT

13. Common Features of Knotweed (con.)
Rhizome
• Rhizome can extend 6 to 8 feet in year
• Rhizomes can lay dormant for up to 20 years

14. Rhizome Cross-Section

15. Rhizome –
Vertical
Cross-
Section

16. Common Features of Knotweed (con.)
• Spread by:
– Rhizome extension
– Distribution of plant parts
• Rhizome pieces – as small as 0.7 g (Brock & Wade 1992)
• Node pieces
– Seeds – not major source in WA. (Miller 2005)

17. Key Distinctions Among Species
• Giant knotweed
– Leaf blades up to 18 inches long and half as wide
– Cordate (heart-shaped) at base
– Straight stem
• Japanese knotweed
– Leaf blade is 8 inches long and almost as wide
– Flat across base
– Zig-zag stem
• Bohemian – blend of two

18. Identification
Good source: Prather TS, Miller TW, Robins
SS, Knotweed shrubs: identification, biology, and
management, Pacific Northwest Extension
Publication 2009

19. Knotweed Badness
• Riparian areas especially vulnerable
• Out-compete other plants => monoculture
• Tree Absence leads to:
– Loss of shade
– Loss of woody debris
• Changes in soil fertility
• Erosion along streambeds and stream banks

20. Knotweed Monoculture
Photo Credit: Justin Knabe, Minnesota DOT

21. Current Control Methods
• Cutting or Removal
• Coverage or Burial
• Chemical

22. Cutting, Removal, Coverage, Burial
• Cutting or removal – probably not practical
except on small scale; high risk of spread.
• Coverage or burial – probably not practical
except on small scale.

23. Coverage is Really Tough
Photo Credit: Popplewell Associates, York, UK

24. Control – Chemical
• Foliar
• Cut stem
• Stem injection
• Stem wipe

25. Knotweed Rhizome Tough to Kill!
Key Problem: older parts of rhizome and dormant
buds are weak sinks. (Bashtanova et al. 2009.)

26. Foliar
• Best to treat after July 1
• Backpack sprayer
• Typical chemicals used are:
glyphosate, triclopyr, and imazapyr

27. Foliar
• Advantages
– Fastest
– Treat small-stemmed plants
– Good control: 81%. (Miller 2005)
• Disadvantages
– Off-target harm: Avg. injury: 68%. (Miller 2005)
– Hard to treat large plants

28. Cut Stem
• Cut stem 5 to 10 inches off ground
• Immediately pour up to 5 ml into hollow of
stem

29. Pouring Herbicide into Cut Stem

30. Cut Stem
• Advantages
– Low cost equipment
– Good control
• Disadvantages
– Time-consuming
– Disposal of green aerial shoots
– Amount of herbicide used

31. Stem Injection
• Use hypodermic or special injector
• Inject up to 5 ml into stem
• Between 1st and 2nd node above ground

32. Stem Injection

33. Stem Injection
• Advantages
– Precision
– No stem disposal
– Efficacy; Avg control: 88% (Miller 2005)
• Disadvantages
– Time-consuming
– Id of treated stems
– Amount of herbicide used
– Cost of equipment
– Non-target injury: 26% (Miller 2005)

34. Stem Wipe
• Either cut stem or leave stem whole
• Abrade stem in some manner near base
• Wipe onto exposed inner tissue

35. Stem Wipe with Foam

36. Stem Wipe
• Advantages
– Low cost equipment
– Efficacy is good; control: 89%. (Miller 2005)
• Disadvantages
– Time-consuming
– Off-target injury: avg = 13% (Miller 2005)

37. Follow-Up Applications
• It seems that all methods of application currently
used require follow-ups for many years
• According to Washington State Dept Agriculture:
“The trend of this data shows a significant
decrease in knotweed following six years of
annual treatments. Despite these dramatic
reductions, knotweed is still present at each
monitoring site.” (Statewide Knotweed Control
Program; 2010 Progress Report)

38. Can We Do a Better Job of
Killing the Knotweed
Rhizome?

39. Rhizome Injection

40. Rhizome Injector
• 6 in. blunt tipped needle
• Metered dosing
• 250 ml capacity (treatment for approximately
125 plants)

41. Rhizome Injection – the Concept
First Premise: Efficacy of any method depends
on herbicide reaching rhizome and roots.

42. Rhizome and Roots

43. Rhizome Injection – the Concept
Second Premise: Efficacy decreases as trans-
location distance increases.

44. Efficacy and Translocation
100%
Efficacy
Decreases
meters
Translocation Distance Increases

45. Translocation Distance
Foliar Application – 3 meters
Stem Injection or Wipe – 20 cm
Rhizome Injection – 5 cm

46. Rhizome Injection – 1st Step
• Access inside hollow stem near ground level
– Cut stem at ground level – dead or living stem; or
– Bend stem at ground level and create opening into
the stem hollow

47. Rhizome Injection – 2nd Step
• Insert needle of injector through septum in
hollow of stem
• Probe down into rhizome hollow as far as
possible

48. Rhizome Injection – 3rd Step
• Inject Herbicide
• I set dose at 2ml
• AquaMaster label, for example, forbids
injection in excess of 5 ml into stem

49. Rhizome Injection
Needle reaches to
below-ground
Internode

50. Inserting Needle into Cut, Dead Stem

51. Injecting into Rhizome
through Cut Stem

52. Inserting Needle into Bent Live Stem

53. Inserting Needle into Bent Live Stem

54. Results?

55. Treated Area

56. Untreated Area

57. Results - Preliminary

58. Results - Priliminary

59. Results - Preliminary

60. Results - Preliminary

61. Healthy Nearby Knotweed

62. Potential Advantages – Rhizome
Injection
1. Injection directly into rhizome – the part of
plant that herbicide must reach
2. Amount of herbicide can potentially be less
3. Eliminate disposal problems – leave live
aerial shoots attached or treat when aerial
shoots are dead

63. Potential Advantages – Rhizome
Injection
4. Extend application season:
– Summer – after July 1 or so
– Fall
– Late fall – after stems have died
– winter
5. Treat fewer stems?
– Depends on amount of translocation

64. Green Shoots
John Lampe – contact:
• john@greenshootsonline.com
• 651-245-4682 (cell)
Website:
www.greenshootsonline.com
• Email or call for copy of
presentation
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