Saltcedar
Information

 Saltcedar Home Page

 Introduction and Spread

 Impacts

 Biology and Ecology

 Management

 download
the Management section
(16 pages 156 kb)

 Restoration in the Southwest

 RFP's and Contracts

 Management Plans

NM Non-native Phreatophyte Control Program

 Literature

Management

Considerations and reasons for saltcedar control

From the 1940s to present the literature is full of countless descriptions of efforts aimed to control saltcedar. A lesson learned early on, but what must still be reiterated, is that there is no single effective control method. Only by use of treatment combinations logically applied over fairly long time periods can one expect to minimize saltcedar impacts. This approach requires flexibility and recognition of local conditions and available technologies, and is often referred to as taking an adaptive management strategy.

On floodplains adjacent to the Rio Grande and Pecos a great deal of work has been conducted by various agencies to reduce saltcedar stands. Vegetation managers realize that saltcedar is not likely to ever be completely eliminated. A more realistic view is that saltcedar is now a part of riparian communities and should be managed in ways to keep it as a minor component in the tree mix.

Agencies and individuals involved in saltcedar management do so for a variety of reasons and they use a wide range of methods to accomplish their needs. To critics, it may seem apparent that there are better ways for a particular agency to attack their saltcedar problem than by using the approach(es) they are currently following. However, there are many considerations besides simply using what seems to be the “best” or a proven saltcedar control method. Equipment availability, financial constraints, available manpower, time needed to complete the task, environmental restrictions, biological limitations, and numerous other factors enter into the decision making process when selecting control procedures. A major intangible influencing why and how an agency proceeds is the institution’s mission and policy framework for decision making. Also important is the manager’s background, previous experience, tradition, and know how.

Management approaches

Control strategies employed within headwater, transitional, or depositional portions of watersheds are typically quite different. For example, in headwater areas an eradication strategy may be emphasized to prevent the downward spread of saltcedar along waterways. In the transitional zone the goal may be to remove saltcedar from a rivers edge in order to enhance water flow and channel movement (Graf 1978). In depositional areas, objectives for saltcedar can vary widely and may include enhancing wildlife habitat (Kerpez and Smith 1987, Ellis 1995, Taylor and McDaniel 1998, Anderson et al. 2003), minimizing a potential fire hazard (Busch and Smith 1995), facilitating better water management for agriculture, (Shrader 1977, Weeks et al. 1987), regenerating native riparian communities (Howe and Knopf 1991, Taylor et al. 1999), or meeting other multiple use needs (Horton and Campbell 1974). From a socio-economic perspective, rural communities often place special emphasis on control to meet agricultural water needs, whereas urban areas identify recreation, fire prevention, flood control, or aesthetics as reasons for saltcedar control.

Commercial or contract considerations

Much of the saltcedar control and restoration work is accomplished by agency personnel or contracted with commercial operators. Skill and expertise among individuals, agencies and companies is often quite different and must be recognized when planning and financing a project. Hand cutting and mechanical treatments, in particular, are very labor intensive and require skilled and conscientious workers. Logistics and costs associated with each project is influenced by a myriad of circumstances but local site conditions, scale of the treatment, equipment type and size, and selectivity required to complete the task influence treatment cost. Workman’s compensation insurance is a significant cost that influences bidding, especially when a large number of workers are required. Bulsterbaum (2005) provides some useful tips and considerations when planning and contracting a saltcedar clearing project.

Root crown – The focal point for control

Saltcedar’s root system is dominated by a root crown that extends about 12-18 inches below the soil surface. Apical buds on the root crown and shallow lateral roots sprout new stems rapidly if aerial portions of the plant are removal. Control methods that damage top-growth but fail to destroy the root crown are considered suppression techniques. These include fire, mowing, grazing by goats or other livestock, defoliating herbicides, foliage feeding insects, etc. Suppression techniques rarely kill saltcedar. Methods that target and destroy the root crown are the only techniques that truly provide plant control.

Mechanical control

A number of mechanical techniques are used to control saltcedar ranging from individual plant treatments (IPT) to broad scale clearing. Individual plant removal is effective on scattered plants at the fringe of a major infestation, saltcedar growing intermixed with desired native trees, and where small isolated pockets of saltcedar occur. IPT is also an effective practice in a follow-up maintenance program where only a few plants have reestablished after earlier control. Broadscale clearing methods are usually conducted using a two-step approach. First, aerial growth is removed, and later root material is destroyed using subsurface implements.

Various kinds of mechanical equipment have been used and tested in New Mexico but the most common IPT’s include hand cutting, grubbing or excavating saltcedar. The most common broadscale clearing treatments include mowing, root plowing, or excavator/mulching. Some devices designed to achieve saltcedar control in one step have been examined in the past. For example, the chem-cut (mower and sprayer in same operation), and chem-plow (root plow and herbicide incorporation; Hollingsworth et al 1972), have been examined but have not been adopted into operational practice.

Individual plant treatments

Hand pulling, hoeing, or digging saltcedar will kill the plant provided the root crown and associated layered roots have entirely been removed from the soil. This practice is most practical on seedlings and young plants. All uprooted material should be stacked and dried and piles burned or mulched. There are some commercial implements available that are practical for uprooting small saltcedar plants but a shovel or hoe are the most common implements.

Hand cutting and chemical treatment, also referred to as the cut stump treatment requires trained chain saw operators and herbicide applicators. Cut stump treatment is used particularly where other mechanical treatments or foliar applied herbicide spraying is limited because of the need to protect native vegetation. Trees should be cut to the lowest practical height (~4 to 6 inch) and the aerial tree portion piled for chipping, mulching, burning or later removal. Current strategies are to hand cut (chainsaw) in winter and to immediately (within 10-15 minutes) apply a solution of 33% triclopyr plus 67% oil (bark, crop or diesel oil) to the surface and evenly around the outside edge of cambial bark material.

Application may be made with a low volume backpack sprayer or by brushing the solution directly onto the cut stump. Treatments have also been made using a hand-held spray bottle that can be attached to the belt of the cutter. Immediately after cutting the tree the operator sprays herbicide directly to the stump. This provides a relatively easy, fast, accurate method of herbicide application by one person actually doing two jobs in one operation. Some commercial operators prefer this method because the person cutting the trees knows where stumps of all sizes are located as opposed to a second person following the cutter with a backpack who might miss a cut surface.

With any herbicide application method, it is imperative that every cut surface be thoroughly wetted in order to obtain root kill. Mortality rates following cut-stump treatments are directly related to care taken when treating cut surfaces. Under optimal conditions control is 60-80 % but because of the difficulty with this method it is not unusual for plant kill to be <40%. Therefore, follow up treatments using ground-based foliar application techniques should be anticipated.

Tractor mounted grubbing implements are especially useful for control of scattered individual trees. The grubbing tool mounted on a tractor’s front hydraulics drive a blade into the soil to sever below the root crown and uproot the plant onto the surface. Grubbed saltcedar should be piled, dried and burned or mulched rather than left on the surface to prevent the plant from re-rooting from adventious buds.

Excavators are used to selectively remove individual trees, including the root crown and portions of the lateral and deeper roots. Operators on this equipment must be skilled in placing the extracting bucket beneath the root crown of the target plant and the opposing hydraulic thumb to grasp the plant so that it can be pulled directly upwards in a vertical motion. Extracting the tree vertically rather than sideways minimizes excessive breakage of the root material at or near the ground surface. On a tap rooted species such as saltcedar, this process is highly effective with control typically ranging from 80 to 90%. Other species of invasive trees (i.e. Russian olive, Mulberry, Tree of Heaven, Siberian elm) that possess shallow root systems without a distinct tap root can also be removed by extraction. However, as a caution, a large portion of their roots typically break off in the soil and they possess apical growing buds. Thus, root re-sprouts are common within a year and follow up control treatments are necessary.

View Excavator Video

Extracted saltcedar may be gathered and chipped using a grinder, or mulched in place. Equipment used for mulching have cutting heads on a rotary drum configured with knife blades or carbide teeth.

Broadscale top removal clearing

Top Removal or Suppression Treatments include mechanical practices that destroy top growth but do not harm the buried root crown and the supporting lateral root system. Thus, mowing, mulching, grinding, surface blading, roller chopping, chaining, bulldozing, shredding, and hand-cutting may suppress saltcedar’s water wastage for a season, but if these practices are not continued or if a follow up practice that destroys the root system is not used, then the plant quickly grows back. The optimum time for mowing is autumn when saltcedar enters winter senesces. A benefit sometimes not appreciated from mowing floodplain areas is the stature of all vegetation is lowered thereby reducing the potential hazard from wildfires (usually human caused) which are common in spring when winds are high. Also, because mowing is repeated annually, saltcedar’s growth and water use is continually suppressed.

Broadscale root treatments

The principal mechanical treatment designed to clear large mature saltcedar stands and destroy the root crown is root plowing and raking. Grubbing, excavating, and mulching in combination with chemical treatment can lead to root destruction over broad areas but these methods are generally considered to be selective or individual plant treatments. Deep tillage practices with a two-bottom plow or off-set disc can keep saltcedar from establishing in new areas or an agricultural field setting. For control of saltcedar thickets, such as those established on the floodplain, the clearing operation is usually done in sequence as follows: aerial vegetation is bladed and cut at the surface > downed aerial debris is stacked and burned > the area is plowed to a 12 to 18 inch (30 to 45 cm) depth to sever the basal crown from deeper roots > root material is raked, piled and burned > the area is dragged and smoothed using a railroad iron or chain over the surface to level the terrain.

Root Plow and Raking has been employed since the 1980s for control of saltcedar monocultures on the Bosque del Apache NWR along the Rio Grande in New Mexico (Taylor and McDaniel 1998). A two-phase approach is followed. In the first phase aerial trunks and stems are cut at the soil surface and piled using a D-7 or D-8 class bulldozer equipped with a front-mounted brush blade. A 3-yd capacity articulating loader equipped with a brush rake working in tandem with bulldozers facilitates piling. Piles are allowed to dry for a month or longer prior to burning. This work is usually accomplished during winter months to avoid harsh hot summer conditions that contribute to equipment over-heating and summer nesting seasons for bird species.

Root plowing and raking, the second phase of control, occurs during hot and dry summer months, usually May and June when root material is subject to desiccation as it is removed from the soil. A 12-ft wide root plow, pulled by a D-7 class bulldozer, is used to sever the root crown from the remaining root mass about 12-18 inches below the soil surface depending on the maturity of the saltcedar stand. A D-8 class bulldozer equipped with a 21-ft wide hydraulic root rake containing teeth 4-ft long in length and spaced 15 inches apart is used to rake root material from the soil surface. The material is windrowed and later piled using the articulating loader. Piles are subsequently burned.

An experienced operator can clear a typical saltcedar stand averaging 10-12 ft in height with plant populations of 3000-4000 plants/acre at the rate of about 6 acres/day. Root plowing is accomplished at a slower rate of about 3 acres/day, while root raking can progress at a rate of about 15 acres/day. Costs for mechanical saltcedar control can vary depending on stand characteristics. Generally, shorter stature, dense stands that are not fully mature will take longer to complete control work than larger trees with fewer stems. Satisfactory control prior to site restoration must reduce plant densities to less than 20 plants/acre (~99% control). To achieve this level of control, sites must often be root plowed and raked twice in opposite directions. Follow-up individual plant control treatments (grubbing or herbicide application) are advised for a 2-year period following initial control work. Costs/acre and percent control for various projects on the BDA refuge based on contracted equipment and labor are provided in Table.

Mulching/grinding and chemical treatment is accomplished in two steps. Mulching reduces the top growth to near ground level. However, saltcedar grows back quickly if a follow up treatment is not applied to destroy the root crown. Herbicide application is one treatment designed for this purpose. After mulching top growth to a ~4 inch stump height triclopyr (Garlon 4 TM ) herbicide mixed with oil and blue dye is sprayed on all intact mulched stump surfaces, in a manner similar to the cut stump treatment. A major difficulty with this procedure is finding all mulched cut surfaces and obtaining satisfactory herbicide coverage on them when they are buried beneath chipped debris. Preliminary data collected from transects in an area where this approach was used on the Rio Grande Bosque (Bulsterbaum 2005), indicates some reduction in saltcedar, but follow up treatment on regrowth was necessary.

View Grinder Video

Mulching and excavator are a combination of practices designed to eliminate top growth quickly by mulching, and then later follow up with extraction to destroy the root crown. Mulching uses mobile high horsepower machinery that operates a high speed rotational drum equipped with cutter teeth. The equipment mows top growth to ground level and simultaneously grinds it into fine segments. The mulching method clears significant treatment acreage for a given time input, which is important when the goal is to reduce fuel loads, thereby reducing the risk of catastrophic fire danger. Mulching operations leave the root intact; therefore saltcedar will re-sprout when growth conditions are favorable. A track mounted excavator is employed to remove the root stock that is indicated by the re-sprouts that are typically 2 to 5 ft in height within the first or second season after mulching. The extraction process is slower compared to mulching and soil disturbance is greater. This treatment option is not immune to further growth and sprouts but preliminary results in the Northern Rio Grande Phreatophyte Control Project (Bulsterbaum 2005) indicate fair to good control.

View Mulcher Video 1

View Mulcher Video 2

Biological control

Biological control is a highly specific technique to manage only one or a few closely related plants. It is most useful in natural areas, rangelands and forests, where the objective is to manage only the target weed without harming other plants. Historically the most common approach has been “Classical” or “Introductory” weed biological control involving the introduction of highly host specific natural enemies (usually insects or plant pathogens) that suppress the weed’s populations in its homeland. This approach is relatively inexpensive, can be permanent, highly host specific, and environmentally compatible. The objective is not to eradicate the weed (which biological control has never done) but to reduce the abundance below the level where economic or ecological damage occurs.

The entire process of biological control of weeds is under careful regulation and oversight by the National Environmental Policy Act (NEPA), the Endangered Species Act, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA-APHIS), by the Technical Advisory Group on Biological Control of Weeds (TAG), a multi-agency group that advises APHIS, and by the Saltcedar Biological Control Consortium. Releases of control agents cannot be made until all regulatory requirements are satisfied and release permits are issued by APHIS.

Saltcedar ranks very high under nearly all of the characteristics generally accepted as qualifiers for biological control: it is an exotic invader, it is not closely related to any native or economically important plants in North America, it causes great losses and has small beneficial values, it occurs in stable ecosystems, and many promising control agents are known in its native range that are highly specific and potentially could be introduced (DeLoach 1989, 1991, 1996; DeLoach and Tracy 1997). The major concern in the use of biological agents to control saltcedar is the possible loss of habitat for the endangered southwestern willow flycatcher (swWIFL) that nests in saltcedar in mid-elevational areas of New Mexico, Arizona and southernmost Nevada (DeLoach and Tracy 1997, DeLoach et al. 2000). A Biological Assessment (DeLoach and Tracy 1997) concluded that biological control is unlikely to adversely affect the swWIFL or any other of the 51 endangered or threatened species that occur in or near saltcedar infested areas of the United States. Furthermore, the saltcedar invasion has caused enormous degradation of, and greatly reduced biodiversity in, the great majority of the vital southwestern riparian ecosystems and is spreading rapidly into additional areas. Saltcedar is a major factor in the decline of numerous bird, fish and other animal and plant species, several of which have deteriorated to the status of threatened or endangered.

Investigations into biological control as an effective and sustainable means of saltcedar control were initiated in the 1960’s in California, and continued in the 1980’s under the direction of Dr. C. Jack DeLoach (USDA-ARS, Temple, Texas; Tracy and DeLoach 1999). Over 400 host-specific potential biological control agents were identified based on overseas associations, of which approximately a dozen were chosen for further study (DeLoach et al. 1996). The saltcedar leaf beetle, Diorhabda elongata, was tested extensively in quarantine to ensure safety with respect to non-target impacts (Lewis et al. 2003, DeLoach et al. 2003), culminating in 1996 in USDA-APHIS approval for experimental field releases. After first evaluating performance and impact in large field cages, in 2001 the beetles were released into the open at 11 infested sites in 6 western states (Dudley et al. 2001). Defoliation at some release sites has been spectacular. Long-term suppression and mortality of defoliated trees is still being studied.

The basic life cycle of the leaf beetle is relatively simple. Adults spend the winter in the litter/soil beneath saltcedar trees, emerging in April and May to feed and to deposit small clusters of eggs on the foliage (Li et al. 2000, Lewis et al. 2003). Three larval stages are spent on the same host (unless defoliation forces larvae to disperse) and take from 2 to 4 weeks, depending on air temperature (Bean et al. 2001, 2003). Fully grown larvae descend and pupate beneath the litter, from which new adults emerge after about 2 weeks to feed on foliage and subsequently reproduce. Two generations per season have been commonly observed in the northern half of the western United States (Lewis et al. 2003), while 3 or even 4 generations can occur in more southern locations. Toward the end of the plant growth season, adults re-enter the litter to spend the winter.

Both larvae and adults feed on the foliage and photosynthetic stems by stripping surface tissue, damaging the plant directly and indirectly causing desiccation and abscission of foliage beyond the feeding point, and complete defoliation occurs when larvae increase to typically high densities of over 1000 individuals on a single plant.

In the northern half of the western United States, beetles are being collected with sweep nets or plucked off of individual branches and transported to new uninfested sites. This implementation program is charged with spreading the beetles over the widest area as rapidly as possible. Because of the concerns about the swWIFL beetles are only approved for release at selected sites on the Pecos River in New Mexico. The US Fish and Wildlife Service will not allow any introductions on the Rio Grande or Gila drainages in New Mexico or anywhere in Arizona.

Seven different ecotypes are being tested to find the beetles best suited to environments in the western United States: including Fukang and Turpan from China, Chilik from Kazakhstan, Posidi and Crete from Greece, Karshi from Uzbekistan and Tunis from Tunisia. The Fukang ecotype has been the most spectacular, defoliating large acreages of saltcedar in the northern half of the western United States. The day lengths in the southern half of the western United States seem to limit the expansion of this ecotype so ecotypes from Greece are being released in the south. Fukang, Posidi and Crete beetles were approved for release in New Mexico in August 2003 on the Pecos River where they are being extensively monitored. Establishment has been variable with some short lived heavy defoliation followed by the disappearance of all beetles.

Additional insects have been identified as potential biological control agents of saltcedar. Several of these have already undergone extensive laboratory testing and may provide a better, or at least alternate, management technique for some of the locations where the leaf beetle has not established very well.

Herbicide control

Herbicides are a primary method of saltcedar control in New Mexico and Texas. Of the estimated 75,000 acres of saltcedar controlled in these states from 1995 to 2006, about 75% were treated with herbicides. Herbicides can be applied to saltcedar by a number of methods including fixed-wing aircraft, helicopter, power sprayers, backpack sprayers, and carpet rollers.

Herbicide application can be conducted by individual landowners, agency managers, or commercial applicators specializing in on the ground or aerial spraying. The potential risks associated with herbicide use have been widely studied in the scientific literature and public press. Proper use of herbicides does not pose a significant risk but improper use can lead to several potential problems. For a more indepth discussion of potential risks, including spray or vapor risks, water contamination, toxicology and characteristic of herbicides used in saltcedar management click on this sentence.

Click here for a list of commonly used herbicides for saltcedar control.

How the herbicide is applied by aircraft or with ground equipment is critical to treatment success. Most important is to obtain complete coverage on the saltcedar foliage. When ground spraying, the terminal ends of all branches, including blooms should be wetted. The interiors of plants should then be laced with the spray solution to complete treatment. For aerial applications, the spray volume should be high to insure maximum spray coverage. Spray nozzles should be fitted to deliver moderate to large sized droplets (range from 450 to 1200 µm). Care must be taken to achieve swath overlap because streaking will occur if this precaution is not taken. The absorption of herbicide into the foliage is relatively slow so by spraying in low wind, high relative humidity, and low air temperature the penetration of the chemical into the plant is increased. Regardless of how saltcedar is sprayed, the topgrowth should remain undisturbed for at least two years after treatment. This is because while the plant may appear dead (i.e. completely defoliated), it is still trying to grow from apical buds near the tips of branches. If branches (topgrowth) are removed the plant will shift its’ stored carbohydrate reserves towards apical root buds and allow the plant to re-sprout.

Basal bark treatments using herbicide mixed with oil and a mist sized adjustable nozzle (X0 to X1 orifice size) to deliver spray to the lower 4-6 inches of stem bark on individual saltcedar plants provides fair control. Triclopyr ester should be mixed with vegetable or diesel oil (50:50 v/v ratio) and sprayed around the surface of every lower stem. Imazapyr is also labeled for this application. The optimum triclopyr or imazapyr spray mixture is not known but a higher dose is needed as plant size/age increases. Basal bark treatments are very tedious and time consuming to apply, and this is especially true when saltcedar is multi-stemmed. Basal bark treatments are more easily made in winter when foliage is shed, but summer treatment is recommended in Texas.

Cut Stump Treatment is often used in areas where mechanical treatments or foliar applied herbicide spraying is limited because of logistical considerations or there is a need to be highly selective and to protect native vegetation. Current strategies are to hand cut (chainsaw) and remove the top growth during winter and to immediately (within 10-15 minutes) apply a solution of triclopyr mixed with bark, crop or diesel oil. The mixture ratio commonly varies (from 33:67 v/v to 50:50 v/v ratio) depending on the number of plants to be treated or the application technique used. The lower ratio is usually used when applications are made with a low volume backpack sprayer or a hand-held sprayer bottle, whereas the higher ratio is used when brushing the solution directly onto the cut stump. With either application method, it is imperative that the cut stump be thoroughly wetted in order to obtain root kill. Mortality rates following cut-stump treatments are directly related to care taken when treating cut surfaces. Under optimal conditions control is 60-80%, but because of the difficulty with this method it is not unusual for plant kill to be <40%. Therefore, follow up treatment using ground-based foliar application techniques should be anticipated.

Foliar spray. Ground application of herbicide(s) to saltcedar foliage can be made with a variety of sprayers including hand-held pump-up or backpack sprayers; cattle or trailer sprayers; or ATV mounted low and high powered sprayer systems. Use an adjustable cone nozzle (X6 to X8 orifice size) that can deliver a coarse spray (large droplets). In general, individual foliar plant spray treatments applied in summer are quicker and easier to make and provide better saltcedar control than basal bark or cut stump sprays.

Saltcedar mortality data collected from 23 NMSU individual plant trials indicated imazapyr at 1% v/v or imazapyr plus glyphosate applied at 0.5 plus 0.5% v/v usually provided more than 90% mortality when sprayed beween June and September (Figure). In eight of nine trials when saltcedar was sprayed in August and September, mortality was at least 99% when sprayed with the 1% v/v imazapyr rate. An indicator blue colored spray dye should be added to the spray mixture to visualize coverage. Plants are sprayed to wet foliage, but not drip. Particular attention is paid to spray all sides of the plant and the terminal ends of all branches, including blooms. The interiors of plants should be laced with the spray solution to complete the treatment.

Although herbicides effectively control a high percentage of saltcedar, they seldom provide complete control. Thus in a dense thicket, often having 3000 plants per acre or more, a 10% survival rate can still leave many of the live trees which will require follow up management. Also, the dead standing stems can be a nuisance. To remove this debris the area can be chained, mulched, roller chopped, burned or left as is depending on the local situations. For maximum herbicide effectiveness, top growth should not be disturbed for at least two growing seasons after spraying.

Aerially applied spray mixtures that render the entire saltcedar canopy to glisten with liquid long after spraying is what commercial applicators strive to achieve for optimum plant control. This can partially be accomplished by equipping the correct spray system to the aircraft and to spray under optimal environmental conditions. The goal is to maximize herbicide absorption and translocation throughout the plant and this is best achieved by wetting the entire foliage surface area with droplets that ideally remain damp for 15 minutes or longer.

Research and practical experience has shown that late summer (August-September) is an ideal time to aerially spray saltcedar. Plants should be healthy, with full foliage that has not been stressed by drought, damaged by hail, or begun to turn yellow late in the season.

Equipped with the correct spray system, either aircraft can be used to successfully deliver a lethal spray mixture to saltcedar. The helicopter is advantageous for spraying “tight” difficult areas that require precision application, such as edges of meandering rivers or saltcedar growing interspersed with native vegetation that must be protected. Fixed-wing aircraft are advantageous for spraying large monotypic blocks of saltcedar, such as on floodplains, where these aircraft can deliver an overlapping spray pattern often at a lower flying cost than the helicopter.

Aircraft equipped with satellite guidance systems and GIS capabilities is very essential when spraying in wildland situations. This alleviates the need for on the ground flaggers and provides detailed maps showing areas sprayed. Remarkable progress has been made with onboard computer systems that allow pilots to adjust spray pressure, flow rates, and other spray operations in the air. Similarly, on-the-ground mixing equipment has become more sophisticated and procedures have been improved to increase cost efficiency and better meet increasingly stringent environmental regulations. As new technologies become available aerial applicators are often the first adopters as they strive to keep their business on the cutting edge. The aerial applicator is a vital key to insure a successful saltcedar control program. Thus, obtaining the most qualified individual to do this critical work is a must.

Fixed wing aircraft have successfully been used to spray floodplain saltcedar along the Pecos near Artesia, NM (about 3,800 acres) and along the Rio Grande on the Bosque del Apache NWR (about 1500 acres). In general, saltcedar control has averaged about 80-90% plant kill. The imazapyr + glyphosate mixture has primarily been used for saltcedar monocultures whereas straight imazapyr has been applied where cottonwood and other sensitive trees are growing. On the Pecos project spraying was conducted by flying Air Tractors (earlier 502 but now 602 series) that were equipped with 66 CP straight stream adjustable nozzles (0.172 orifice size) on a boom that fit about 70% of the wing span. Spraying was accomplished at a high volume (~7 gpa) and with relatively large spray droplets (>450 µm). An overlapping spray swath pattern is critical to obtain sufficient herbicide coverage on saltcedar, thus care was taken not to allow the spray swath to exceed 50 ft.

Precision aerial application is a unique feature provided by helicopters. They have principally been used to spray saltcedar growing on the edge of the meandering Pecos from Santa Rosa, New Mexico to near Grandfalls, Texas (about 13,000 acres along 400 river miles sprayed from 1999 to the present). Helicopters have also been extensively used to spray saltcedar along the Rio Grande, Canadian and Ute Creek in New Mexico. North Star Helicopter has been responsible for much of the application work on the Pecos and Rio Grande. This company has been particularly innovative in designing both on-the-ground and on-board computer support systems (Trimble GPS guidance system, variable rate flow meter, display unit for GIS display). Spray accuracy and precision is enhanced by use of a boom that is partitioned into 1/3^rd increments so that either outside edge or directly under the helicopter can be used to spray separately or combined. The boom is fitted with Accu-flow nozzles that can be adjusted to deliver large droplets (>1000 µm) that result in a spray swath pattern that is square (deposited straight down). North Star Helicopter, Inc. has assembled an excellent ground support system (tanker trucks with landing decks, separate water and herbicide mixing tanks, computer driven flow meters, etc.). Combined, this advanced equipment design provides for a productive and environmentally sensitive spraying operation.

Because saltcedar grows close to water its habitat is nearly always considered environmentally sensitive. This is especially true where it occurs in close proximity to agricultural or residential land, or it occupies areas with endangered species (plant or animal) and other critical riparian habitat concerns. Precision aerial application has gained added significance in large scale saltcedar control programs because pilots must be able to identify property boundaries and locate avoidance zones. GPS and GIS systems are available today to assist operators to precisely apply herbicides within a matter of ft from where it is intended to be delivered. With today’s technology it is possible to pre-map areas to be sprayed and pre-program the on-board spray system so that the herbicide is sprayed only on defined treatment areas. This has added a new dimension with respect to restoration of riparian habitats where pre-planning and mapping are critical to eventual success (Taylor and McDaniel 2003).

Helicopter Video 1

Helicopter Video 2

Fit into saltcedar management plan

Saltcedar control is but one necessary step in the overall process that agencies must concern themselves with in the management of a river system. Thus, approaches for managing the plant should be integrated into the strategic plan covering all aspect of river management. Before any control option can be employed, financial and logistical considerations must be addressed and a budget prepared to keep cost within reasonable limits. Limited budgets may require prioritizing areas of greatest concern. Regardless of the approach adopted, anticipate unforeseen problems and build flexibility into operational programs to improve effectiveness. Once the desired objectives are obtained, anticipate that yearly follow-up work may be necessary to prevent reinfestation.

Integrated approaches

Most often a single method is not effective in the sustainable control of saltcedar. A successful long-term management program should be designed to include combinations of mechanical, cultural, biological, and chemical control techniques. There are many possible combinations that can achieve the desired objectives, but these choices will have to be tailored to the site, economics, and management goals. Sometime the control techniques must be in a particular sequence to be successful. A strategy that is flexible and adopts actions that meet specific needs is often referred to as taking an adaptive management approach.

Herbicide-burn (-mechanical) saltcedar control

A lesson learned after nearly 75 years of experience with saltcedar is that this introduced plant is here to stay and that no single method provides sustainable plant control. Successful long-term management programs should expect to include a combination of mechanical, fire, and chemical (and perhaps in the future biological) control techniques. This is particularly true when riparian vegetation restoration is a major objective and preventing saltcedar reestablishment is critical to achieving long-term native plant stability.

Numerous integrated approaches have been developed for the management of saltcedar (Table). These include judicious use of herbicides in combination with mechanical control techniques. Fire has been employed as a first step for removing aerial saltcedar growth before further treatment with a chemical or mechanical control method; or as a late step in the removal of dead debris. With saltcedar, it seems that only the imagination limits the perturbations or combination of methods that can be used for plant control.

The herbicide-burn saltcedar control program is relatively new and has emerged from an experimental phase to use as a practical control tool on large monotypic tracts (McDaniel and Taylor 2003). The herbicide treatment includes 2 quarts of Arsenal/Habitat or a 1 quart Arsenal/Habitat plus 1 quart glyphosate mixture applied in water with a 0.25% by volume nonionic surfactant and a 0.07% by volume drift control agent (Duncan and McDaniel 1998). Applications can be made with either fixed-wing or helicopter aircraft in August or September prior to fall color change when plants are actively storing carbohydrates in root systems in preparation for winter dormancy. Moderate temperatures (60-80oF), high relative humidity (65-90%), and light winds (3-7 mph) are ideal to maximize herbicide activity. Applications should be made only to mature saltcedar stands to maximize surface area for herbicide interception and translocation to meristematic regions in the plant. Herbicide applications to recently burned or disturbed stands will result in poor control due to disproportionate aboveground to belowground biomass ratios. For maximum control, sites receiving herbicide treatment should not be disturbed for 3 years to allow maximum plant herbicidal efficacy.

A prescribed burn follows herbicide treatment to remove aerial trunks and stems. Initial stand canopy coverage should be 60-70% to carry the fire and to maximize fuel consumption. Moderate temperatures (64-85oF) and relative humidity (30-40%), and light winds (3-7 mph) are important environmental conditions for burning standing dead (herbicide treated) saltcedar to assure fuel consumption (>98%) and safe burning conditions. Such conditions coincide with the summer rainy season, primarily in August. With preparation of 50 ft firebreaks surrounding treated areas, prescribed burning can be conducted safely due to the high fuel moisture content of adjacent untreated saltcedar. Long-term saltcedar control using the herbicide-burn control technique has been 93% or greater. Costs/acre and percent control for various projects on the Bosque del Apache National Wildlife Refuge are provided in Table 2.

If conditions necessary for prescribed burning can not be met, follow up mechanical treatments, such as chaining, cabling, bull dozing or roller chopping can be used to down dead aerial trunks and stems. In some cases stacking the debris and burning the piles may be desired or necessary. Along the Pecos River near Artesia, NM, costs/acre for chaining averaged about $7.00/acre and roller chopping about $10.00/acre 3 years after aerially spraying saltcedar.

Costs associated with control methods

Tamarix clearing is accomplished using a combination of herbicide, burning, and mechanical control techniques (McDaniel and Taylor 2003). Complete land restoration costs range from $1,852 to $3,200 per acre($750 to $1,300 per ha) on extensive floodplain areas on the Bosque del Apache NWR along the Rio Grande (Taylor and McDaniel 1998a). For Tamarix control alone, a combination of herbicide and burning cost from $114 to $225 per acre($46 to $91 per ha) with expected control around 92% (McDaniel and Taylor 2003). Root plowing plus raking costs range from $300 to $700 per acre($121 to $283 per ha) with plant control exceeding 97%. Tamarix infestations intermixed with remnant stands of desirable trees, shrubs, or herbaceous cover are cleared with cut-stump treatments on a contractual basis averaging between $2,000 to $2,500 per acre ($809 to 1012 per ha) (Taylor and McDaniel 2003).

Additional links and information:

Control of Saltcedar Regrowth with Carpet-Roller Applied Herbicide download (151 pages 801 kb)

Next page