Since 1983, a volunteer program funded mainly by the Desert Protective Council has significantly contributed to saltcedar control efforts in California and several neighboring states.
A summary of the volunteer program seems warranted at the start of this discussion, because the author has no academic training or professional experience in the disciplines of botany, pest control or habitat management. The observations and recommendations submitted below are therefore the product of hands-on experience -- of organizing and supervising volunteer work parties at about 45 sites over the past 14 years -- plus discussions with numerous professionals working on the problem.
I first learned of the saltcedar problem and control techniques in 1980 at Death Valley National Monument, where resource manager Pete Sanchez and associates were engaged in a 10-year campaign to eliminate saltcedar from Eagle Borax Spring. This effort commenced in the early l970's, after the saltcedar invasion had depleted the surface water flow and stressed native mesquite trees near the spring, located on the west side of the salt playa at the foot of the Panamint Mountains.
Saltcedar removal at Eagle Borax Spring was completed during late 1982 with informal assistance from a Sierra Club group. By then, restoration of the spring had produced dramatic results: surface water had returned to nourish marsh vegetation and migrating waterfowl, and the mesquite trees were again healthy.
In the early 1980's, the saltcedar control effort at Death Valley was the only such program active in California, with the exception of an incipient campaign directed by Mark Jorgensen at Anza-Borrego Desert State Park. Before or during this period, saltcedar removal was attempted at other units of the National Park Service -- at Canyonlands, White Sands, Big Bend -- but none with the long-term commitment or success evident at Death Valley.
Starting in early 1983, the volunteer program sponsored by the Desert Protective Council helped to publicize control methods employed at Death Valley to other agencies in other areas. As new herbicides and techniques were tested or became available, technology exchange between professional land managers was expedited via volunteer work projects, on-site consulting, and widespread distribution of my "Tamarisk Newsletter" issued occasionally between 1986 and 1994.
To demonstrate the scope of the volunteer program, below are listed saltcedar removal projects either initiated and/or completed or assisted by volunteer work groups:
|1983-4,91||Afton Canyon||BLM Barstow Area|
|1989-90||Ash Meadows NWR||US Fish & Wildlife Service|
|1993||Pahranagat NWR||US Fish & Wildlife Service|
|1994||Owens River||Los Angeles DWP|
|1983-4||Saline Valley||BLM Ridgecrest (now NPS)|
|1983-4,93||Fort Piute||BLM Needles (now NPS)|
|1984,95-6||Big Morongo Canyon||BLM Palm Springs Area|
|1984-90||Thousand Palms Canyon||The Nature Conservancy|
|1984-92||Amargosa Canyon||The Nature Conservancy|
|1986-95||Camp Cady Wildlife Area||Calif. Dept. Fish & Game|
|1987,9||Tecopa area||The Nature Conservancy|
|1988-9,93||Sheep Camp Spring||Private|
|1991-2||Dos Palmas||The Nature Conservancy|
|1991-2||Zion Canyon||Zion National Park|
|1992||Sacaton Canyon||Lake Mead NRA|
|1992||Rainbow Bridge||Glen Canyon NRA|
|1992-4||Bonanza Spring||BLM Needles Area|
|1992,94||Cimarron Spring||BLM El Centro/Anza-Borrego DSP|
|1993-4||Bear Canyon||Picacho SRA|
|1994||Piute Canyon (White Mtns)||BLM Bishop Area|
|1994||Burro Spring||Lake Mead NRA|
|1995||Buzzard Spring||Joshua Tree National Park|
|1984||Corn Spring||BLM Palm Springs Area|
|1984-91||China Ranch/Willow Spring||Private|
|1988||Hidden Palms||The Nature Conservancy|
|1989-95||Carrizo Canyon||Calif. Dept. Fish & Game|
|1990-91||Pushwalla Canyon||The Nature Conservancy|
|1990-91||Middle Canyon||Catalina Island Conservancy|
|1991||Garlic Spring||Fort Irwin Army Base|
|1991||Dead Mountains||BLM Needles Area|
|1991-3||Murray Canyon||Agua Caliente Reservation|
|1993-4||Granite Spring (Mojave Rd)||BLM Needles Area|
|1993||Jacumba Jim Spring||BLM El Centro|
|1993||Pixley NWR||US Fish & Wildlife Service|
|1993-4||Magnesia Falls Canyon||Calif. Dept. Fish & Game|
|1994||Four Frogs Spring||BLM El Centro|
The 7+ years of inactivity at some BLM sites resulted from a July 1984 injunction by the 9th Circuit Court of Appeals barring all herbicide applications on BLM and Forest Service land and the subsequent delay needed for preparation of a comprehensive environmental impact statement and site- specific environmental assessments.
Volunteer participants for these projects were recruited mostly through publicity by or cooperation of the following organizations:
The volunteer program has been recognized by service awards from the California Nature Conservancy (1987) and California BLM Desert District Advisory Council (1992), and by articles in the Los Angeles Times (1989) and Sunset Magazine (September 1996).
Procedures for removing saltcedar by selective (non-aerial) herbicide applications are now a mature technology, and there is no need for further experimentation.
Over the 14-year history of the volunteer program, the "herbicide of choice" for cut-surface applications has progressed from Tordon RTU ("ready-to-use") to Tordon 101 mixed in water, Garlon 3A, Garlon 4 mixed in water, Garlon 4 mixed in diesel oil, Pathfinder (Garlon 4 in solvent), and now either Garlon 4 in vegetable oil or Pathfinder II. At each stage, assessments have been made of suitable mixing ratios, seasonal efficacy, cost and user friendliness.
The currently preferred formulation is 25% Garlon 4 (triclopyr), diluted in cheap vegetable oil at a 1:3 ratio. Assuming Garlon 4 can be purchased for about $90 per gallon, the cost of this mixture will be about $26 per gallon, which normally will treat hundreds of tree stumps. Alternatively, Pathfinder II is the equivalent ready-to-use mixture produced by DowElanco, containing 25% Garlon 4 in vegetable oil, with a retail price of about $30 per gallon.
Unfortunately, Pathfinder II lacks the bright red dye that was included in the original Pathfinder formulation. To expedite identification of treated stumps, applicators may choose to add oil-soluble dye to the herbicide mixture or, outside California, dilute with Penevator basal oil which is colored. Garlon 4 is not registered for aquatic use, so for cut-surface applications near surface water, the recommended herbicide is Monsanto's Rodeo at full- strength concentration. The disadvantage of applying Rodeo, compared to diluted Garlon 4, is that it is more expensive. The definition of "aquatic" use refers to the potential for trace amounts of herbicide to enter surface water; stumps located near but not rooted in water can be legally treated with Garlon 4 provided that none enters water -- although land owners and agencies may require greater separation distances to ensure compliance.
In most cases a target tree or sapling should be cut within 6 inches of the ground surface using a chainsaw, brush cutter or sturdy anvil-blade lopping shears. Stump heights should be as close to the ground as feasible, without allowing saw teeth or lopper blades to be dulled or damaged by rocks or sandy soil.
The stump surface should be lightly sprayed with herbicide within several minutes of cutting. Care should be taken to wet the entire circumference of the bark's cambium layer. On large-diameter stumps, the interior woody portion can be left untreated to conserve herbicide.
In rocky stream courses, stumps may require cutting higher that 6 inches to avoid chainsaw blade damage. In such cases, to increase herbicide efficacy, not only the cut surface but also the bark on the stump should be sprayed down to ground level, but not to the point of runoff. This additional treatment is effectively the basal-bark method described below.
Large trees with isolated trunks can be more efficienty treated by girdling, i.e. by making shallow, overlapping cuts into the bark around the trunk base using a hatchet or chainsaw, and then lightly spraying the entire cut surface with herbicide. Substantial amounts of labor can be saved by not felling and removing large trees. However, many large saltcedar trees have multiple trunks radiating from the root crown, and most limbs must be removed to obtain access for the herbicide treatment.
For applying herbicide to stumps, a small finger-trigger spray bottle is usually adequate. High-quality bottles can be purchased at janitor supply stores. Larger 1 to 2 gallon hand-pump pressurized garden sprayers with a hose and wand-type nozzle may be useful for faster work, as when a single applicator is following several chainsaw operators in a saltcedar thicket.
It is important to use hand-held rather than larger backpack-type sprayers: leakage from backpack sprayers is more likely to contact the applicators, and connecting hoses on the back side are likely to be snagged on tree branches and pulled off, causing rapid uncontrolled drainage of the herbicide tank.
The efficacy of Garlon 4 in cut-bark applications shows no clear seasonal dependency. Beyond the label's caution that treatments may be less effective during times of drought, saltcedar removal may be scheduled when outdoor working conditions are most comfortable -- usually in the autumn and spring seasons, but also during winter when the tree is dormant. However, where saltcedar is intermixed with native trees, its identification is more difficult during winter months when the tree is leafless; conversely, during autumn and spring months, saltcedar recognition is aided by the plant's yellow foliage or pink flowers.
Over the past several years, the low-volume basal bark treatment method described on the Garlon 4 label has been successfully applied to saltcedar. It is an alternative to the labor-intensive cut-stump method on trees with trunk diameters less than 6 inches. Normally the lowest 12 inches of trunks are sprayed -- without cutting -- with 20% to 30% Garlon 4 in oil.
The basal bark technique has been employed extensively in remote mountains canyons of Lake Mead National Recreation Area by Curt Deuser (702-293-8979), using a mixture of 25% Garlon 4 in Penevator basal oil; and at Coyote Canyon in Anza-Borrego Desert State Park under the supervision of Mark Jorgensen (619-767-4962), with the same concentration carried in kerosene.
In the volunteer program, the basal bark method has proved valuable at Camp Cady Wildlife Area on the Mojave River east of Barstow, in treating saltcedar resprouts growing from large debris piles left by a major flood in 1993. Applications of 20% Garlon 4 in diesel oil cancelled the need for laboriously dismantling the debris piles.
Advantages of the basal bark method are that less labor is required, compared to cutting and stump-spraying; and there is no generation of cuttings that must be piled on dry bare ground or dead vegetation where they cannot root.
The disadvantage of basal bark spraying is that more herbicide mixture must be applied to each stem -- perhaps 5 times more than the cut-surface method -- because more surface area is treated and there is unavoidably more wastage. Also, treatment success is less definitive, and if a first treatment is unsuccessful, a second treatment of a surviving sapling will require more time and herbicide than treatment of a short resprouting stump.
The appropriate choice between cut-surface and basal bark applications will depend on the balance of labor resources and financial resources. In the volunteer program, the use of power saws followed by workers to pile cuttings will remain a fast and efficient method to remove saltcedar trees on level ground. But a smaller work force on rocky terrain should find the basal bark method to be clearly advantageous.
Although the Garlon 4 label directions do not refer to foliar applications, the treatment of resprouting stumps may be considered a variation of the basal bark method. Probably resprouts are most effectively treated when they have grown to lengths of 4 to 8 inches -- when the surface area of stems and leaves is sufficient to absorp enough herbicide to kill the root crown, but not so large that the consumption of herbicide and applicator time is excessive. Mixtures of 10% Garlon 4 in water or diesel oil are adequate on previously treated stumps; but for the more vigorous stems that resprout after fires, a 20% concentration in oil is preferable for effective control.
In planning a saltcedar control program, the first rule is to attack outlying plants first rather than the dense thickets. Reasons for this strategy are outlined in my abstract for an October 1992 presentation to the California Exotic Pest Plant Council:
The strategy of attacking outliers first may seem obvious to some, but it counters the normal human tendency to react more to obvious problems than to potential problems. The two best reasons for this strategy in long-term projects are (1) efficiency and (2) psychological reward.
Efficiency means gaining control of the problem with a minimum of effort. The first objective of exotic species control is to stop population growth and prevent dispersal into new areas. The outlying plants are the main agents of seed dispersal. Even if some seeds travel widely, most land close to the parent plant rather than far from it.
By removing outliers first, we avoid a larger problem several years later. Conversely, in established concentrations, waiting another few years has not much effect: the exotic plants will be larger, but they will compete against each other, rather than native plants, and the rate of population increase will be slower than in outlying areas.
Psychological rewards comes from doing the easy work first, and making rapid progress initially. At an early stage, we establish large areas that are now mostly free of weeds, that we can monitor for regrowth while we work on the heavily infested areas. That early sense of accomplishment is important when the work becomes tedious and the total obligation looks overwhelming.
Currently this control strategy is being systematically implemented by the Inyo County Water Department in removing saltcedar from northern Owens Valley.
Desert areas most amenable to saltcedar control are (1) canyons and river channels subject to intense flooding and (2) isolated springs that are never flooded.
The susceptibility of a stream channel to erosive flooding should be evident from the age and size structure of the trees on its banks. A typical history of variable episodic flooding will result in seedlings or relatively young saplings growing on the channel floor, and progressively older and larger trees encountered higher on the banks.
Along flood-prone streams, saltcedar removal should start with larger trees located high on stream terraces that are likely to survive future floods and reseed the stream floor; younger trees and saplings growing lower in the channel can be ignored as they eventually will be washed away. To be most effective, removal work plans should be opportunistic with respect to flood events: for example, after trees located above the five-year flood level are eliminated, subsequent work can be delayed until a erosive flood does occur, after which a concentrated effort is made to remove the surviving trees.
Around isolated desert springs that are never flooded, saltcedar removal must be complete to be effective. But because seeds are generally not viable for longer than one year, once accomplished, the rehabilitation should be permanent, with only minor surveillance needed to remove seedling derived from distant seed sources.
One potential problem of spring rehabilitation is that increased water flow resulting from partial saltcedar clearance may flood new areas and cause new seedling growth outside the area of original infestation, thus increasing the ultimate amount of work needed for control. This sequence of events occurred both at Eagle Borax Spring in Death Valley and at Red Rock Canyon State Park in California. The lesson to be learned is that saltcedar clearance near springs should be completed in a single winter season, if possible. Otherwise, cutting should proceed inward from the perimeter, with trees closest to the spring saved for last; and if water flow returns or increases during summer months before clearance is completed, flowering branches should be cut off without ground-level herbicide treatment to curtail seed production.
Saltcedar control will be most difficult, and perhaps impossible, around reservoirs with fluctuating water levels and on river courses which flood enough to cause widespread seed propagation, but not erosively enough to uproot established trees.
Under favorable conditions the mortality rate of saltcedar after cut-surface herbicide treatment should exceed 95%. Less successful applications are usually attributable to not cutting the bark circumference completely or low enough to ground level, or not spraying soon enough after cutting.
Some amount of regrowth is inevitable. A follow-up visit to treat resprouting stumps is always necessary several months to a year after an initial treatment. In some cases during the spring months, a treated stump will produce short stems before dying. Therefore follow-up inspections should be scheduled after 3-4 months have passed, so that there is no uncertainty over which stumps are dead and which are alive.
Saltcedar trees on floodplains can be more difficult to kill, requiring several treatments. The root systems are more extensively developed near the ground surface, due to repeated scouring and removal of limbs by floods, and can send up shoots where none existed at the time of initial treatment.
Although proper application technique is important, it is necessary to find a balance between working with thoroughness and working with speed. When confronting shallow lateral roots or partly exposed root systems, for example, it is more efficient to work quickly on the first pass; then, after seeing what survives, one spends more time on follow-up visits at treating the more inaccessible roots.
The following recommendations are my contribution to the "Proceedings of the Saltcedar Management Workshop" held on June 12, 1996 in Rancho Mirage and sponsored by the University of California Cooperative Extension and California Exotic Pest Plant Council:
My primary topic will be: what type of areas are appropriate for volunteers, as opposed to paid staff or convict labor. The main considerations are scenic value, project size and environmental sensitivity. First, volunteer work trips are partly recreational, so scenic quality is important. In desert riparian areas, I would equate scenic value with topography. I think nearly any desert canyon would attract volunteers; whereas the flatter areas, even with significant habitat value, will attract less interest, at least on a repeat basis.
Second, it is preferable to give volunteers a project that is small or low density, where they can see tangible progress after a day's work. If the work gets monotonous, that's acceptable if workers are paid money; but all that volunteers obtain is psychological reward, a sense of accomplishment, so the project manager should restrict the scope of work to provide that.
Third, environmentally sensitive areas may be good for volunteers, compared to convict labor. By environmentally sensitive, I mean near water or abundant native vegetation. Volunteers are capable and responsible people who can follow directions and identify plants on their own. Conversely, when clearing a dry monoculture of saltcedar, that's a good place to use prison crews which need closer supervision.
In recruiting volunteers, I take the attitude that volunteers deserve first-class treatment. So I try to offer amenities to make the experience more comfortable or more interesting -- free or reserved campsites, or hot showers, or 4WD access into areas normally closed to the public, or a guided hike or tour after the work session. In planning a trip I negotiate these amenities with the land manager and then publicize them in my promotional writeup.
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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
Conference proceedings hosted by the National Invasive Species Information Center