by Susan Maloney of Campaign for Old Growth
August 22, 2007
The California State Parks department and the County of Humboldt are coming under increasing scrutiny for a proposal to spray herbicides on the south fork and main stem of the Eel River to eradicate purple loosestrife, a highly invasive weed that can change ecosystem dynamics and is very difficult to eradicate. The herbicide that Parks and the county plan to use is called imazapyr.
Purple loosestrife
Photo: www.invasive.org
There are many concerns regarding this controversial proposal. In light of the recent rains we just experienced in Humboldt County, it seems impossible to insure that no herbicide will enter our waterways. The company who manufactures this chemical under the name "Habitat" states, "water treated with Habitat may not be used for irrigation purposes for 120 days after application..."
Although $18,000 has been earmarked for four weeks of spraying and monitoring over two years, the Parks Department claims it is too costly to undertake manual removal.
The plan will require spraying for at least three years, possibly up to 10 years.
Even if the State Parks Department and the County of Humboldt carry out the plan in this area, what is being done to address this issue upstream and downstream?
According to the Northwest Coalition for Alternatives to Pesticides, "Imazapyr can persist in soil for over a year. Persistence studies suggest that imazapyr residues damage plants at concentrations that are not detectable by laboratory analysis."
Imazapyr moves readily in soil and has contaminated surface and ground water following aerial and ground forestry applications.
Small amounts of imazapyr (as little as 1/50 of a typical application rate) can damage crop plants.
Imazapyr exposure also has the potential to seriously impact rare plant species, said NCAP.
In addition, more than a half-dozen weedy plant species have developed resistance to imazapyr.
Although Parks has been working on this issue for three years, they have only made the public aware of the spraying program recently.