controlling invasive knotweeds using low-volume foam herbicide · green shoots, llc saint paul,...
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Controlling Invasive Knotweeds Using Low-Volume Foam Herbicide
John LampeGreen Shoots, LLC
Saint Paul, Minnesota
2014 Upper Midwest Invasive Species ConferenceDuluth, Minnesota
Oct. 20-22
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Overview
• Non-Chemical Control
• Chemical Control
• Focus on: Low Volume Foam Herbicide
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Knotweed Colony at Southwood
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Knotweed – Grows in Tough Conditions
Photo Credit: Popplewell Associates, York, UK
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Knotweed Rhizome Extension
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Non-Chemical Control
• Not practical except with small infestations
• Danger of vegetative spread
• See King County, Best Management Practices (2008)
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Chemical Control
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Knotweed Rhizome – Tough to Kill!
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Chemical Control: Key Problem
Older parts of rhizomes are weak sinks Bashtanova et al. 2009.
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LiveAerial Shoot
LiveAerial Shoot
Dead Aerial Shoot
Winter Buds
Winter BudsLateral
Buds
Lateral Buds
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LiveAerial Shoot
LiveAerial Shoot
Dead Aerial Shoot
Winter Buds
Winter BudsLateral
Buds
Lateral Buds
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LiveAerial Shoot
LiveAerial Shoot
Dead Aerial Shoot
Winter Buds
Winter BudsLateral
Buds
Lateral Buds
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LiveAerial Shoot
LiveAerial Shoot
Dead Aerial Shoot
Winter Buds
Winter BudsLateral
Buds
Lateral Buds
Can herbicide reach the weak sink buds?
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Chemical Control Methods
• Stem injection
• Cut stem
• Foliar
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Key Herbicides
• Glyphosate – aquatic label
• Triclopyr – aquatic label; only foliar
• Imazapyr – aquatic label; only foliar
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Stem Injection
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Stem Injection
• Use hypodermic or special injector
• Inject up to 5 ml into stem
• Between 1st and 2nd node above ground
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Stem Injection
• Advantages:– Precision
– No stem disposal
– Avg control: 91-100 % (Prather + Miller 2009)
• Disadvantages:– Time-consuming
– Identifying treated stems
– Difficulty in treating small stems
– Non-target injury: 26% (Miller 2005)
– And . . .
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Biggest Disadvantage of Stem Injection
• Requires 5 ml of herbicide per aerial shoot
– Equivalent to cut surface application on 10 to 15 inch woody stem. AquaMaster Label.
• May explain 26% non-target injury found by Miller.
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Cut Stem
• Cut stem 5 to 10 inches off ground
• Immediately pour up to 3 ml into hollow of stem
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Pouring Herbicide into Cut Stem
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Cut Stem
• Advantages:
– Low cost equipment
– Control? (Miller did not test)
• Disadvantages:
– Time-consuming
– Disposal of green aerial shoots
– Amount of herbicide used
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Foliar
• Advantages– Fastest application method
– Decent control: 81%. (Miller 2005)
– No disposal issues
– Less herbicide used
• Disadvantages– Off-target harm: Avg. injury: 68%. (Miller 2005)
– Hard to treat tall plants
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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)
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How Can Methods Be Improved?
• Reduce repeat applications
• Reduce quantity of herbicide used
• Reduce off-target harm
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We Have Been Trying Several Methods
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Rhizome Injection
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Injecting into Rhizome through Cut Stem
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Rhizome Injection
Needle reaches to below-ground Internode
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Herbicide Used
• AquaMaster – glyphosate; 54% a.i.
• Dose at 2ml
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Results?
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Not very impressive
• I would guess around 70% to 80%
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Other New Methods Being Explored
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Bend and Treat with Foam Herbicide
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Large Foam Herbicide Dispenser with Foliar
Nozzle
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Treat Regrowth with Low Volume Application of Foam
Herbicide
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Foam Stream Ejected from Dispenser – Reduced Drift
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What is Low Volume?
• Use more herbicide (about 4% a.i.) and less water volume.
• Cover 10% to 30% of foliage.
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Why Low Volume?
“The most consistent application factor that can increase glyphosate efficacy is lower carrier volumes.” Young 2006.
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Deposits Foam on Leaves –Virtually No “Fines”
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Foam Herbicide Clings to Leaf –No drops to bead off 42
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Herbicide Spreads on Leaf 43
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Herbicide Slowly Dries on Leaf –
increasing absorption
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Before: dense knotweed colony
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After: Small, isolated knotweed plants
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Approximately 11 months after single treatment
Native Pilewort dominates now
Scatteredknotweed
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Our Mission: To
recognize
opportunities and
provide leadership
to make our region
a vibrant, place-
based model for the
nation.
563-864-7112; www.northeastiowarcd.org
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Use on Japanese knotweed along Paint Creek in Northeast Iowa
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• “We had an excellent result at the Hardees site, I'd say 80-90% effective. I just foam treated the resprouts on 9/30. The resprouts covered aprox. 10% of the area sprayed last year. It took 1/2 liter of mix.”
• “The west bank that had been 95% stem injected had more resprouts, aprox. 25% of the area. That side took 1 liter of mix to treat.”
Report from Richard Kittelson from the Northeast Resource, Conservation and Development Organization:
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Testing By Dr. Timothy Miller at Washington State University
• Late Summer 2014
• Comparing Spray and Foam Herbicide
• Bohemian and Himalayan knotweed
• Herbicides:
– Rodeo (glyphosate)
– Habitat (imazapyr)
– Perspective (aminocyclopyrachlor)
– Milestone (aminopyralid)
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WSU testing (con.)
• Used 1 liter per plot with foam herbicide
• Used 2 liters per plot with spray
• I.e., using ½ as much foam herbicide as spray.
• Plots (I believe are 20 by 20 feet)
• Research is not funded by Green Shoots; we did provide WSU with a dispenser
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Early WSU Results – Percent Control Determined by Defoliation
Type 2 WAT 4 WAT
Foam 51% avg. 69% avg.
Spray 46 avg. 66 avg.
Note: Averages across all herbicides used and two species of knotweed.
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Why Might Foam Work Better?
• Foam is well suited for low volume applications– Less dripping
– Slower drying of herbicide
– Foam clings tenaciously to foliage
• More surfactant used
• Key Benefit: Virtually eliminates drift
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55
Green Shoots
John Lampe – contact:
• 651-245-4682 (cell)
Website: www.greenshootsonline.com
• Email or call for copy of presentation