5/10/2021

Managing Japanese Knotweed

Randy Prostak, UMass Extension Weed Specialist UMass Extension Weedinar Series May 13, 2021

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JAPANESE KNOTWEED JAPANESE KNOTWEED

Common name: Japanese knotweed - BEST you might hear - Japanese bamboo Mexican knotweed Mexican bamboo

Scientific name: - Polygonum cuspidatum - Reynoutria japonica - Fallopia japonica

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JAPANESE KNOTWEED

Native to Japan & other parts of Asia, not Mexico

Japanese knotweed is NOT a grass, it is a broadleaf weed in the knotweed or smartweed family (Polygonaceae), same plant family as rhubarb and buckwheat. Japanese knotweed Polygonum cuspidatum

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Other knotweed relatives:

giant knotweed: - Polygonum sachalinense - Fallopia sachalinense - Reynoutria sachalinense

bohemian knotweed: - Fallopia × bohemica, hybid (P. cuspidatum & P. sachalinense)

Note: increasingly more common in NE giant knotweed Polygonum sachalinense

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giant knotweed Polygonum sachalinense giant knotweed Polygonum sachalinense

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Means of reproduction

- asexually (primary): vegetatively propagated by rhizomes

- sexually: by seed, significantly less Japanese knotweed giant knotweed important than vegetative propagation by rhizomes

- shredder leaf and stem material even less significant

Bohemian knotweed 11 12

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Habitat Japanese Knotweed Management

- moisture or wet soils Strategy and/or strategies you implement are largely determined by the size and location of - often associated with wet areas the Japanese knotweed population!!!!! - wetlands - stream & river corridors, riparian areas - forest edges - roadsides - abandon agricultural land

- management areas are commonly WPA jurisdiction, requiring Conservation Commission approval

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Non-chemical Japanese Knotweed Control Japanese knotweed plant - frequent cultivation or digging (equipment material disposal often required)

- repeated cutting/mowing - slow spread & - contractors bagged & landfilled reduced vigor - on site: - pile and dry on site (tarp below) - required time frame?? - composted on site - deep bury Carbohydrate Starvation: - prevent photosynthesis - deplete stored energy for rhizomes

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farmplasticsupply.com

Lumite - lumiteinc.com

6 Mil

24 feet by

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farmplasticsupply.com Disturbance is a 24 feet by major factor in invasive plant 8 Mil establishment!!!

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Non-chemical Japanese Knotweed Control - new emerging strategies - MeshTech Disturbance can be problematic!! Japanese Knotweed Solutions Ltd, Radcliffe, Manchester, UK Do your best to prevent the - ¼ inch box wire for agriculture disturbance of soil and leaf-litter layer! supplier, garden center or home store.

Herbicides might be a better option in some situations or attempts can be made to cover the disturbed area.

Remember -- Carbohydrate Starvation??? 21 22

Knotweed Biological Control Predator Exclusion Experiments Knotweed psyllid – Aphalara itadori

Paired‐treatment setup Roadside Habitat Meadow Habitat

• Approved for introduction in North America in 2020 • Kyushu strain feeds preferentially on Japanese knotweed (also can feed on Bohemian knotweed) • Hokkaido strain feed preferentially on Giant knotweed

• Released in Europe and Canada • (Shaw et al. 2009; Djeddour and Shaw 2010; Fung et al. 2020; Jones et al. 2020) © Moth Nature Forest Understory Habitat “Riparian” Habitat Parking Area Habitat Laboratory

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Special Thanks To: Elkinton Laboratory • Jackson Christopher‐Callaghan • Roy Van Driesche

Fritzi Grevstad – Oregon State University

UMass Greenhouse Staff • Christopher Joyner • Daniel O’Neil

Questions? Contact Dr. Jeremy C. Andersen [email protected]

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JAPANESE KNOTWEED CONTROL # glyphosate - flowering (late summer): first sign of bud formation thru to first hard frost

Japanese knotweed management Step 1: cut to ground in late May to early June without herbicides is very difficult and time consuming. - reasons for spring cut to ground: 1. remove previous years dry stems 2. remove some plant energy 3. shorter height as treatment time

AWARENESS OF OPTICS - what about pollinators??

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JAPANESE KNOTWEED CONTROL not mowed, tall Other herbicides??? and flowering imazapyr: Arsenal aminopyralid: Milestone

mowed: shorter and easier to treat, stems from previous years absent

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Glyphosate Products Formulations JAPANESE KNOTWEED CONTROL Not approved for near water: - Roundup Pro - turf & ornamentals surfactant with - stem injection: - other post-patent generics known toxicity to - increase in herbicide aquatic organisms - increase in labor costs Approved for near water: - easy to go “off-label” - Rodeo (Corteva formerly Dow Agrosciences) - Roundup Custom for Aquatic and Terrestrial Use (Bayer) - GlyphoMate 41 Weed & Grass + Aquatic Herbicide (PBI Gordon) - Glyphosate 5.4 (Alligare)

WHAT IS THE DIFFERENCE???? POEA polyoxyethylene tallow amine a.k.a polyethoxylated tallow amine

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Invasive knotweeds: Japanese, Bohemian, giant knotweeds: Optimum suppression of invasive knotweeds with Milestone herbicide is obtained when applications are made to plants that are at least 3 to 4 feet tall. Results of field trials conducted in the western U.S. indicate that high volume applications (100 gpa or greater) of Milestone at 7 fl oz/A or a spot treatment rate up to 14 fl oz/A applied in summer will provide good control of invasive knotweeds. In the upper Midwest, mowing in summer followed by fall application of Milestone (prior to frost) provided the best control. Infestations of invasive knotweed that are mowed should be allowed to regrow to at least 3 feet in height prior to herbicide treatment. Monitoring and follow-up aminopyralid - MILESTONE herbicide treatments on regrowth will be necessary to control resprouts and achieve long-term control.

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JAPANESE KNOTWEED CONTROL Thank You for Your Attention!! All strategies will likely require multiple years Have a Great 2021 Season!! of implementation for long term effect control. DILIGENCE IS CRITICALLY IMPORTANT!!!!!! ???? ????

[email protected] 413-577-1738

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