Columbia County false indigo bush removal on Tucan

The Columbia County Weed Board used this grant to develop and apply protocols to control false indigobush (Amorpha fruticosa) on 35.5 acres along 2 miles of the Tucannon River. False indigobush (Amorpha fruticosa) is a Class B Noxious Weed in Washington & spreads easily by seed while establishing a monoculture along aquatic systems. The current extent of its infestation along the Tucannon River, which is migratory & rearing habitat to threatened steelhead, bull trout & spring/summer & fall Chinook salmon runs, is extensive. Research has shown that native riparian habitat is beneficial to salmonid species by providing food, shelter, low temperature and shade that corresponds with fish camouflouge. Simply stated, false indigobush is detrimental to salmonid & other fish species who require a diversified stream ecology to survive and its spread is unacceptable.

Primary first year objectives of the project were to determine the extent of false indigobush on the Tucannon River and to establish protocols for its removal. Several different herbicides and application methods were tested to determine the most effective and cost-efficient approach to controlling the weed. The herbicides used were Garlon, Rodeo, Milestone, and Arsenal. Tests showed that Milestone was the most effective in treating Indigo bush with Garlon coming in second, although none provided optimal control. The Indigo bush was removed two ways: digging it out of the ground, and mowing it then treating it with herbicide. Mowing and treating proved to be the most cost effective way to control the Indigo bush. Revegetation techniques were established after false indigobush removal. Educational material was circulated to residents regarding the need to eradicate/control false indigobush and the importance of native vegetation to Tucannon River fish.

The goal of the project is to restore native riparian vegetation along salmon bearing streams. The objective of the project is to restore natural streamside vegetation, improve stream temperature, reduce erosion, filtration, and recruit large woody debris.