Injection of Herbicides into Rhizomes of Knotweeds and Other Invasive Species
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Transcript of 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
John LampeGreen Shoots, LLC
Saint Paul, Minnesota
Upper Midwest Invasive Species ConferenceOctober 29-31
La Crosse, Wisconsin
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.
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
Common Species of Knotweed
• Japanese knotweed (Polygonum cuspidatum)
• Giant knotweed (Polygonum sachalinense)
• Bohemian knotweed (Polygonum x bohemicum) – hybrid
Identification
Good source: Prather TS, Miller TW, Robins SS, Knotweed shrubs: identification, biology, and management, Pacific Northwest Extension Publication 2009
Knotweed Colony
Knotweed Leaves
Photo Credit: Steve Manning, Invasive Plant Control, Bugwood.com
• Dark green leaves• Un-toothed• alternate
Knotweed Stems - Young
Knotweed Stem - Dry
Photo Credit: James H. Miller, USDA Forest Service, Bugwood.com
• Hollow internodes• Septum separating• Up to 2 in. dia.
Knotweed Rhizome
Rhizome
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)
Knotweed Badness
• Riparian areas especially vulnerable
• Out-compete other plants => monoculture– Loss of trees– Changes in soil fertility– Erosion along streambeds and stream banks
Knotweed Monoculture
Photo Credit: Justin Knabe, Minnesota DOT
Knotweed Rhizome Extension
Photo Credit: Popplewell Associates, York, UK
Knotweed Rhizome Extension
Knotweed Rhizome Extension
Non-Chemical Control
• Not practical except with small infestations
• Danger of vegetative spread
• See King County, Best Management Practices (2008)
Chemical Control Methods
• Foliar
• Stem injection
• Cut stem
Key Herbicides
• Glyphosate – aquatic label
• Triclopyr – aquatic label; only foliar
• Imazapyr – aquatic label; only foliar
Knotweed Rhizome Tough to Kill!
Key Problem: older parts of rhizome and dormantbuds are weak sinks. (Bashtanova et al. 2009.)
Knotweed Rhizome – Tough to Kill!
Foliar
• Advantages– Fastest application method– Decent control: 81%. (Miller 2005)
• Disadvantages– Off-target harm: Avg. injury: 68%. (Miller 2005)– Hard to treat tall plants
Stem Injection
Stem Injection
• Use hypodermic or special injector• Inject up to 5 ml into stem• Between 1st and 2nd node above ground
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)
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.
Cut Stem
• Cut stem 5 to 10 inches off ground• Immediately pour up to 3 ml into hollow of
stem
Pouring Herbicide into Cut Stem
Cut Stem
• Advantages– Low cost equipment– Control? (Miller did not test)
• Disadvantages– Time-consuming– Disposal of green aerial shoots– Amount of herbicide used
Stem Wipe
• Inconsistent Results (Miller 2005)
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)
How Can Methods Be Improved?
• Reduce repeat applications
• Reduce quantity of herbicide used
• Reduce off-target harm
We Have Been Trying Several Methods
Rhizome Injection
Rhizome and Roots
Rhizome Injection
Needle reaches to below-ground Internode
Herbicide Used
• AquaMaster – glyphosate; 54% a.i.
• Dose at 2ml
• Well below AquaMaster label rate for hollow stem injections: 5 ml
Inserting Needle into Cut, Dead Stem
Injecting into Rhizome through Cut Stem
Inserting Needle into Bent Live Stem
Results?
Ongoing Rhizome Injections
• Winter and early spring injections did not produce results
• Late spring injections show promise
• Currently doing tests – late summer and Fall
Other New Methods Being Explored
Cut, Bend, and . . .
Treat with Foam Herbicide
Munch, Bend, and . . .
Treat with Foam
Tromp, Wait, and . .
Treat Regrowth with Foliar Applied
Low Volume Foam Herbicide
Bend and Immediately Treat . . .
Stems and . . .
Foliage
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
Rhizome Injection Methods
• Less time consuming
• Less herbicide
• Injecting into rhizome – will this improve treatment success?
Bent Stem Wiping Methods
• Exposing vascular tissue
• Foam herbicide sticks to stem
• Uses a lot less herbicide
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Green Shoots
John Lampe – contact:• [email protected] • 651-245-4682 (cell)Website: www.greenshootsonline.com • Email or call for copy of
presentation