Mark Floyd,
Oregon State University writer
The near-eradication three decades ago of tansy ragwort, one of Oregon’s most problematic invasive species, was considered a crowning achievement because of innovative biological control methods.
But this year, tansy ragwort has flourished throughout western Oregon through a combination of weather conditions and a “down cycle” for the three insects used to control this toxic weed, continuing a disturbing recovery trend that began six years ago. Suddenly, a new…