DESCRIPTION
The Columbia County Weed Board received a SRFB grant in 2009 to test the effects of several False Indigo Bush control methods. The grant originally purposed to control false indigobush (Amorpha fruticosa) along 13 miles of the Tucannon River. False indigobush is a noxious weed in Washington and spreads easily and overtakes other plants along streams and waterways. This threatens salmon and other fish species that need more diverse habitat to survive. The extent of the indigobush infestation along the Tucannon River was unknown at the time of the project so several locations in the lower river were treated with a method which involved the cutting of the plant by hand followed by two -three chemical treatments over the following three years. Following treatment it is important to plant the treated area with a canopy forming plant type which can shade the ground and prevent the regeneration of indigo bush from the seed bank.
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.
Tucannon River Population
