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October 16, 2006

“Dip and clip” method controls weeds at Lake Tahoe

Trespassers are invading the Lake Tahoe Basin, but a novel approach can stop them in their tracks.

   Users should hold their clippers with  the flat surface facing downward to maximize the amount of herbicide applied to the cut stem.
  

Users should hold their clippers with the flat surface facing downward to maximize the amount of herbicide applied to the cut stem.
Photo by Sue Donaldson

Three perennial weeds are slowly infiltrating one of California’s scenic gems. Perennial pepperweed, Dalmation toadflax, and diffuse knapweed are present in the Lake Tahoe Basin. These and other weeds have been planted as ornamentals by those unaware of their invasive nature. Scientists are concerned that invasion by these weeds may result in increased erosion and impacts to lake water quality.

Basin-wide efforts to locate and control weed infestations are under way. With funding from the University of California Exotic/Invasive Pests and Diseases Research Program, Jennifer Erskine-Ogden, postdoctoral researcher from University of California, Davis, Mark Renz, weed scientist from University of Wisconsin-Madison, Sue Donaldson, water quality specialist from University of Nevada-Reno Cooperative Extension, and Bill Frost, natural resource advisor from University of California Cooperative Extension in El Dorado County, are studying low-impact control measures to control these prolific weeds.

Historically, few herbicides have been used to manage weeds at Lake Tahoe because of its environmental sensitivity. Currently, hand pulling is the method used to get rid of the pests, but it’s only moderately effective unless it’s repeated for several years. Even then, it can cause a lot of soil disturbance near the plant making the plant community more susceptible to further invasion and increasing the potential for erosion and sediment inputs to the lake.

“Invasive weeds reduce recreational values and uses, take over agricultural lands, displace native species, decrease wildlife habitat, and cost millions of dollars for treatment,” says Renz. “Our ultimate goal is to provide land managers in the Lake Tahoe Basin with a successful control measure that prevents the continued spread of these invasive perennials and is accepted by the community as an environmentally friendly management option.”

Renz and Frost have confirmed the effectiveness of a new environmentally sensitive herbicide delivery system, referred to as "dip and clip," that simultaneously clips weeds and deposits herbicide on the remaining stems. This technique is an expensive management option, but the added safety measure of specific application to weed stems only will make this a viable option for using herbicides in the Lake Tahoe Basin.

“This method offers the Lake Tahoe Basin Weed Coordinating Group a much-needed alternative to traditional weed control methods while ensuring lake water quality is protected,” says Donaldson.

Renz and Frost have produced a pamphlet, A Precision Method for the Control of Perennial Herbaceous Species in Sensitive Locations, (PDF* 536KB) to explain how to effectively manage perennial weeds in sensitive areas.

*You need Adobe Acrobat Reader version 5 or later to view or print this PDF. If this software is not installed on your computer, you can download a free copy of Acrobat Reader.

Resources

High-resolution image (908KB) "Users should hold their clippers with the flat surface facing downward to maximize the amount of herbicide applied to the cut stem." Photo credit: Courtesy of UC Statewide IPM Program, Sue Donaldson.

High-resolution image (1,016KB) "After donning protective gloves, Jennifer Erskine-Ogden, postdoctoral researcher, University of California, Davis, carefully dips the clipper blades into the herbicide solution. The solution should not drip onto the ground." Photo credit: Courtesy of UC Statewide IPM Program, Sue Donaldson. Photos are for use with this release only. All other uses see Legal Notices.

Contacts

Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

Jennifer Erskine-Ogden, Postdoctoral Researcher
University of California, Davis
(415) 812-3417

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