Saltcedar (Tamarix spp.) has impacted many native plant communities in the western United States and has become a significant problem on many national wildlife refuges including the Kern and Pixley National Wildlife Refuges. The Kern Refuge has a significant infestation of saltcedar with approximately thirty percent of the refuge covered with this invasive plant. The Pixley Refuge has only a minor infestation which is isolated to spots within the 950 acre wetland unit.
A variety of techniques have been developed for the treatment of the saltcedar. The best technique for the control or eradication of this plant can be site sensitive and vary depending upon objectives and habitat needs. These techniques include fire, mechanical removal with bulldozers, root rakes or root plows, and chemical treatment as well as a combination of these techniques. In many situations, when the use of heavy equipment or fire would do more harm than good or when the infestation is small or sparsely spread, the cut-stump treatment, although time consuming, may be the best alternative. This is the case in the riparian unit on the Kern National Wildlife Refuge where saltcedar is interspersed with desirable riparian trees such as cottonwoods and willows and in the wetland unit on the Pixley National Wildlife Refuge where trees are found in isolated locations.
The cut-stump technique used on the Kern Complex involves cutting saltcedar trees and shrubs to ground level and spraying stumps with the herbicide Garlon 4. Methods of removal include chain saws, brush cutters, lopping shears and other hand tools. Stumps are then sprayed using hand-held spray bottles. The herbicide must be applied to the stump immediately following cutting in order to reach full effectiveness. The herbicide is most effective while the tree is actively growing and translocating nutrients. The treatment should be applied after the plant has bloomed and prior to dormancy. Cutting the tree outside of this time frame is effective in removing the bulk of the biomass but the resprouts will need to be treated with chemical the following year to in order to kill the plant. Many saltcedar plants grow in a bush or multiple stem tree. To help insure all stumps or stems are covered with herbicide it is useful to add a dye to the chemical mixture which tags each stump when sprayed allowing the applicator to see the amount of coverage and which stumps have been sprayed. The most efficient procedure is to have the crew work in groups of three to five people. Generally, one person to cut the tree, one or two people to pull trees as they are cut and one or two people to spray the stump as soon as access is available. This technique is time consuming and not recommended for extremely large infestations.
One concern that is discussed when controlling exotic plants is the effects on non-target species and possible effects to endangered or sensitive species. Many techniques such as burning, widespread mechanical treatment or broadcast spraying of herbicides can have some impact on non-target plants and animals. When using the cut-stump treatment for saltcedar many of these concerns can be set aside. In many cases the saltcedar out competes all native vegetation in the local vicinity reducing the risk of impacting non-target plants. In addition, this methods utilizes a pesticide delivery method which reduces if not eliminates non-target effects. Individual saltcedar plants are selected and the herbicide is sprayed at a range that limits drift to non-target plants.
Most national wildlife refuges do not have the personnel available that the cut-stump method requires unless the saltcedar problem is small. Therefore, it is important to locate an alternative source of labor to conduct this work. Over the past six years, alternative labor sources such as volunteers and prison labor have been used on both Kern and Pixley Refuges to cut saltcedar. The Corcoran prison crew was used in 1990 to cut and treat saltcedar in a wetland unit on Kern. Volunteers from the Tulare Audubon Society have been used on Pixley. A third labor source available to the Kern Complex is the state supported California Conservation Corps (CCC).
The CCC is a state department which was established in 1976 to protect and restore California's natural resources by employing California residents between the ages of 18 and 23. A portion of their funding is generated by sponsor partnerships for specific work projects. Starting in 1993 the CCC began cutting saltcedar in the Riparian Unit on the Kern Refuge as part of a Riparian Restoration and Rehabilitation Project. Phase 2 of the project deals with saltcedar control within the 320 acre riparian unit. This plan will ultimately lead to defined water management goals for riparian habitats, increased acreage of native riparian vegetation, potential reintroduction of native species and preservation of habitat for giant slough thistle.
The control techniques outlined in the plan are being conducted by the CCC under the guidance and training of refuge staff. The use of the CCC on the Kern Refuge has been successful thus far. They have effectively controlled the saltcedar adjacent to the main riparian channel for approximately mile. The CCC has been working this area for four consecutive years (1993-1996). Their time commitment ranges from two to four weeks per year which is dependent upon their work load and funding availability.
The first three years the refuge received non-base funding (non-game and challenge-cost share monies) to support the CCC work. The fourth year no funding was available but the CCC volunteered one week of time to the project. The non-game funding provided in 1993 purchased one week of labor from a twelve person CCC crew with the CCC donating an additional three weeks of labor. In 1994 Challenge Cost Share money was provided to continue the funding of this project. The U.S. Fish and Wildlife Service paid CCC $5,000.00 for the first week to cut and treat saltcedar; the CCC donated the labor for the second week. The work was continued in 1995 with the same funding source. In 1996 no money was available to fund the CCC although they did donate several days in the spring.
The cut-stump treatment can be a useful tool in the fight against saltcedar but its effectiveness is dependent upon the quality and reliability of the workforce. Three sources of hand labor have been used on the Kern Complex, volunteers, prison crews, and the California Conservation Corps crews. Individual crews have their strengths and weaknesses. Many times a volunteer work force will be more effective because they may have a greater motivation to kill the plant and improve the habitat than a prison crew. Depending upon the location, volunteers to do this type of high intensity labor may be difficult to find. Therefore, a prison crew or an organization such as the California Conservation Corp may provide a more dependable labor source for projects which will span longer periods of time.
When working with volunteers or groups which may only work occasionally, it is important to keep the crew motivated. If the project is so large that it is overwhelming, keeping the crew motivated will be difficult. Breaking a large project into smaller projects which can be easily completed provides the crew with a sense of accomplishment and a willingness to return and do more work.
When working with prison crews or organizations such as the CCC effectiveness of the treatment is directly related to the crew leader and the work attitude of the crew. To help ensure proper treatment it is critical that the herbicide be applied within seconds of the tree being cut. Some crews are more diligent than other at applying the herbicide which relates directly to the percent kill. Overall the Kern refuge has had good success using CCC crews with the exception of 1996. The 1996 crew was pulled by the CCC crew leader from the complex three days into the project and did not return. The crew members were slow and lackadaisical about their work and very little of the work was completed. This crew has been the exception rather than the rule for the quality of crews working on the refuge complex. Overall the quality of work the CCC provides has been good.
Prior to utilizing the alternative labor sources for saltcedar control, an evaluation of cost effectiveness for the specific project should be undertaken. These expenses will vary based upon available labor, equipment needs, and availability of herbicide selected. Expenses include costs for labor, herbicides, tools, fuel for powered equipment, safety equipment, and miscellaneous expenses for equipment maintenance.
Labor sources can range from free to approximately $1,000.00 or more per week. In addition to the crew labor, staff time to oversee, supervise and train the crew must also be considered. Some crews will need greater amount of staff supervision than others. Groups such as the CCC are able to provide a competent crew leader which can reduce the amount of staff time needed to oversee the project. Volunteer groups will require staff involvement to supervise the crew for the duration of the project unless a volunteer is sufficiently knowledgeable about saltcedar control. The cost of herbicides also needs to be considered. Garlon 4, which is the herbicide used on the Kern Complex, costs approximately $85.00/gallon. Cost effectiveness will vary based upon the cost and quality of labor. If a good, hard working crew is obtained, this can be a relatively cost effective method for dealing with some saltcedar problems.
In closing, the use of alternative labor force can be successfully utilized in the control of saltcedar if the time is taken to research and plan the project.
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For information on the outcome of this workshop or integrated weed management in the Pacific Region (Region 1), U.S. Fish and Wildlife Service, Portland, OR, contact: Scott_Stenquist@fws.gov
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