This document is a presentation on methods for controlling invasive knotweed species. It discusses current chemical control methods like foliar spraying, stem injection, and cut stem treatments. It notes the disadvantages of these methods, like using large amounts of herbicide and causing off-target damage. The presentation explores ways to improve methods by reducing the quantity of herbicide used and minimizing off-target impacts. It describes experiments with injecting herbicides into knotweed rhizomes and bending stems to expose tissue before treatment. The goal is developing more effective and sustainable control techniques.
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Injection of Herbicides into Rhizomes of Knotweeds and Other Invasive Species
1. Injection of Herbicides into
Rhizomes 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
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2.
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
• Background on Knotweed
• Current Chemical Control Methods
• How Can Our Methods be Improved to:
– Reduce quantity of herbicide used
– Reduce off-target harm
5. Common Species of Knotweed
• Japanese knotweed (Polygonum cuspidatum)
• Giant knotweed (Polygonum sachalinense)
• Bohemian knotweed (Polygonum x
bohemicum) – hybrid
6. Identification
Good source: Prather TS, Miller TW, Robins
SS, Knotweed shrubs: identification, biology, and
management, Pacific Northwest Extension
Publication 2009
12. 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)
13. Knotweed Badness
• Riparian areas especially vulnerable
• Out-compete other plants => monoculture
– Loss of trees
– Changes in soil fertility
– Erosion along streambeds and stream banks
18. Non-Chemical Control
• Not practical except with small infestations
• Danger of vegetative spread
• See King County, Best Management Practices
(2008)
27. 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.
28. Cut Stem
• Cut stem 5 to 10 inches off ground
• Immediately pour up to 3 ml into hollow of
stem
30. Cut Stem
• Advantages
– Low cost equipment
– Control? (Miller did not test)
• Disadvantages
– Time-consuming
– Disposal of green aerial shoots
– Amount of herbicide used
32. 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)
33. How Can Methods Be Improved?
• Reduce repeat applications
• Reduce quantity of herbicide used
• Reduce off-target harm
43. Ongoing Rhizome Injections
• Winter and early spring injections did not
produce results
• Late spring injections show promise
• Currently doing tests – late summer and Fall
55. 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
56. Rhizome Injection Methods
• Less time consuming
• Less herbicide
• Injecting into rhizome – will this improve
treatment success?
57. Bent Stem Wiping Methods
• Exposing vascular tissue
• Foam herbicide sticks to stem
• Uses a lot less herbicide
58. 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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