Dear Flower,

First, I apologize for taking so long to respond to your report. This reporting hotline is still fairly new and we are adding more responders to try and respond to reports in real time. I hope I address your concerns about tansy below. Please read the entire email and let me know if you have any more questions.

Thanks for reporting. As you are very aware, tansy ragwort is very common in western Oregon. As you also have noted, biological controls are present to help in controlling this weed. There are two primary bio-agents for tansy one you noted; the cinnabar moth and the other is the tansy ragwort flea beetle. Since these two agents have been released, all control efforts by governments and groups have been discontinued. These two agents keep tansy populations below an economic level through out WESTERN Oregon.

Tansy ragwort plants and the bio-control agents that work on them cycle up and down in almost opposite directions. The bio-control agents build up so high and feed on tansy so heavily that the tansy populations go down severely. Then the amount of feed for the bio-control agents (in this case Tansy) starts getting so low that the bio-control agents start to die off from lack of food and the tansy populations start to increase severely. It seems we are in the part of the cycle where the plants are on a major rebound. Within the next few years, the biocontrol agents should respond positively to this increase in feed (tansy) and bring the plants back down below the levels we saw a few years ago before this recent increase.

Please see the document at this link for a more in depth explanation of this process. This document was written in 2000 during another big increase. You will need to copy the link from this response and paste it in the URL line of your internet browser.

http://extension.oregonstate.edu/coos/Livestock/Tansy%20OCA%202-00.pdf

Also,
if you travel to central and eastern Oregon and see tansy please submit a report, tansy is a high priority for control east of the Cascades in Oregon.

And lastly,
We at EMSWCD are setting up an Early Detection and Rapid Response program to detect and control new noxious weeds before they get a hold in Multnomah County. Send me an email if you are interested in attending one of the trainings that are planned for the spring.

Thank you!

Lucas Nipp, East Multnomah SWCD
lucas@emswcd.org
503-539-5764

Lucas Nipp
Dec. 1, 2008, 7:46 a.m.