We recently hired a licensed chemical applicator to apply herbicide to our forest property. We were informed by that individual that our neighbor has Japanese Knotweed on his untended property. Should be we concerned?

Reporter
Oct. 19, 2010, 11:53 a.m.

Hello Mr. Dunlap,

Thanks for reporting this infestation of knotweed. First let me apologize for the time it has taken me to respond to your hotline report. Knotweed is a significant problem invader, particularly in riparian communities within Clackamas County. The Clackamas Soil and Water Conservation District is working with regional partners to map and catalog known infestations of knotweed to help prioritize future control efforts.

Knotweed can be very difficult to control once it becomes established. Preventing this species from becoming established on your property is a good strategy. I recommend monitoring your property for small plants and treating them as soon as they are discovered.

Knotweed typically spreads along streams and waterways moving upstream to downstream. If your neighbor is upstream from you there is a good chance that thier infestation can spread downstream onto your property. If your neighbor is downstream from you there is a good chance that there is another population upstream of both of you, that is dispersing downstream.

The Conservation District currently offers technical information to local landowners to help them develop a management strategy that is effective for their particular site conditions and needs. If you or your neighbor would like assistance please contact us at the Conservation District.

Also please check these online resources to better manage knotweed on your property.

http://www.skamaniacounty.org/Noxious_Weeds/TNCreport.htm

http://www.imapinvasives.org/GIST/ESA/esapages/documnts/polycus.pdf

When working with knotweed it is important to avoid spreading root and stem fragments into streams and rivers. These fragments will float downstream to grow and develop into new knotweed plants.

If you are planning to use chemical control methods avoid drift into streams and adjacent native vegetation. Also be sure to read and follow the label. The label is the law. So be sure you follow all label directions, recommendations, and restrictions.

Again thank you for reporting this invader. Feel free to contact me if you have additional questions.

Sincerely,

Sam

______________________________________

Samuel Leininger

WeedWise Program Manager
Clackamas Soil & Water Conservation District
221 Molalla Ave. Suite 102
Oregon City, OR 97045
503-210-6006
sleininger@conservationdistrict.org
www.conservationdistrict.org

______________________________________

Samuel Leininger
Dec. 21, 2010, 6:09 a.m.