• Introduction
• Santa Clarita Site Map
• Removal Methods
• Herbicides
• Documents
• SCARP Maps
• SCARP Project

Introduction

The Ventura County Resource Conservation District (VCRCD) partnered with the City of Santa Clarita to remove invasive plants such as arundo (Arundo donax) and tamarisk (Tamarix spp.) from a 297-acre site on the Santa Clara River. This site is located between Newhall Ranch Road and Magic Mountain Parkway. It is intersected by McBean Parkway. [See map below]

The primary threats to the remaining riparian habitat of coastal southern California are invasive non-native plant species, including arundo and tamarisk. Arundo is a giant reed native to the Indian subcontinent. It was introduced to the western United States by Spanish settlers. Arundo has the capability to spread rapidly, forming large contiguous root masses covering several acres, effectively crowding out native riparian vegetation. This results in lower biodiversity of plant life, eliminating crucial habitat for birds, fish, and other wildlife that use riparian waterways. Tamarisk is a native to south Eurasia and was introduced at the turn of the century for cultivation. It is an aggressive, woody invasive plant species that is relatively long-lived and can tolerate a wide range of environmental conditions once established. Stands of tamarisk generally have lower wildlife values compared to stands of native vegetation and have allelopathic effects by causing the surface soil to become highly saline, thus impeding future colonization by many native plant species. Over time, arundo and tamarisk have spread rampantly throughout riparian forests in southern California. The Santa Clara River Watershed is no exception; arundo and tamarisk present in the Santa Clara River and all its major tributaries, including San Francisquito Creek. The removal of these plants will reduce flooding and wildfire hazards as well as improve the habitat for native plants and wildlife.

The California Conservation Corps and the Los Angeles Agricultural Commissioner performed the removal work. The project was funded by a Costa-Machado Water Act of 2000 [Proposition 13] grant from the State Water Resources Control Board.

This project focused on a small section of the watershed - if you are interested in future projects, please contact Noreen Cabanting, Project Manager at 805 386 4685 or email Noreen.Cabanting@vcrcd.org. Back to top.

Santa Clarita Site Map with Target Vegetation

Click here for full-size Santa Clarita Site Map. Back to top.

Removal Method Information

Cut and Paint

Equipment Needed:Loppers, chainsaws, brushcutters, or similar equipment can be used to cut the plants. A paintbrush, sponge dauber, or small hand pump sprayer can be used to apply herbicide.

Personnel Required: A large group can do the initial cutting and removal of plants. At least two people are needed to re-cut stems and apply herbicide efficiently. One person trained in the use and handling of herbicides is needed to supervise the remaining workers.

Instruction: Tamarisk trunks and arundo canes are cut within one foot of the ground and removed using hand tools. Herbicides must be applied to the cut stem surface immediately after cutting (within one to two minutes) and may be applied by spraying or painting/daubing. For arundo, full-strength Aquamaster® is often used with a cloth-covered wand, sponge, or hand mister. For tamarisk, backpack spraying using Garlon 3A® and an oil concentrate mixture (25 percent Garlon 4 and 75 percent oil concentrate) has been effective. Herbicides must cover the entire surface of the stem in order for this method to be successful (Neil 1992).

Timing: This method can be implemented throughout the growing season, although it may be most effective when the herbicide is applied in the late summer or early fall.

Appropriate Use: This method can be applied in most cases. It may be the most effective method when working in mixed vegetation or in the riverbed where water may be present. This method is also ideal in hard to reach areas since it is not necessary to pack in heavy tools. It is also appropriate for supervised volunteer groups because it is simple and safe to work in close proximity.

Pros: Highly successful in the first year with few resprouts. This method is highly selective with little risk of drift of herbicide onto non-target plants or sensitive wildlife species. There is little soil disturbance associated with this method.

Cons: Initial labor and herbicide costs are higher than other methods, although less retreatment is required. Back to top.

Cut/Mow, Re-Sprout, and Spray

Equipment Needed: Pressurized sprayers and booms attached to ATVs or backpack sprayers would be required to foliar spray stands of arundo and tamarisk. Cutting the canes can be done by hand or with power tools depending on the size of infestation. Heavy machinery, such as a flail mower, is appropriate for larger infestations. Loppers, chainsaws, or brushcutters are recommended for smaller sites.

Personnel Required: A single person or group can use this method, depending on the size of infestation. One person trained in the use and handling of herbicides is needed to spray.

Instruction: A crew will first cut or mow the arundo and/or tamarisk down to the ground. The crew will return after a sufficient period has elapsed (approximately one to two months) to allow for re-sprouting. The resprouts, ideally two to three feet in height, will then be sprayed with herbicide using either mobile booms or backpack sprayers.

Timing: The cutting should occur in the late fall months, or during winter dormancy, with resprouts sprayed during the following spring. Follow-up spraying should be scheduled when re-growth is still small and easy to reach, approximately one to two months after cutting.

Appropriate Use: This method can be used in most situations where arundo and tamarisk is not heavily intermixed with native vegetation.

Pros: There is low soil disturbance associated with this method if hand tools are used. There is also less risk of herbicide drifting onto native vegetation than when spraying full-grown canes.

Cons: Waiting for resprouts after cutting can be impractical when working in remote areas. Large equipment (such as flail mowers) can substantially disrupt the soil and damage native, non-target species and habitat. Back to top.

Herbicides

Glyphosate

Glyphosate is the active ingredient in the retail products Rodeo©, Aquamaster©, and Roundup© and is effective in control or eradication of both arundo and tamarisk. The USEPA has approved Rodeo© and Aquamaster© for use in aquatic environments. Roundup©, conversely, is only approved for use in areas where water is not present.

Glyphosate works by interfering with a plant's protein production system and disrupting metabolic functions, particularly energy use and growth (Tu et al. 2001). It is systemic in action, transferred through the plant’s vascular system from the tissues that absorb it to all parts of the plant. Glyphosate is most effective when used on perennial plants, such as arundo and tamarisk, when applied in the late summer and fall when the plant is entering dormancy, as this permits transmission of the herbicide to the plant’s root system (TADN 1999). Glyphosate is a non-selective herbicide, generally affecting all species of vascular plants when directly applied; however, it is strongly adsorbed by soil particles, which prevents it from excessive leaching or from being taken-up from the soil by non-target plants (Tu et al. 2001). This can permit its use in areas of intermixed native and invasive plants. Although it is highly toxic to plants, glyphosate has exceptionally low toxicity to mammals, birds, and fish (Tu et al. 2001). Back to top.

Triclopyr

Triclopyr is the active ingredient in Garlon© and Pathfinder© formulations, and is sold as Access© in other areas. Garlon 4 and Pathfinder II are approved for terrestrial habitats. Garlon 3A is approved for use in use in and around standing water such as marshes, wetlands, and around the banks of ponds and lakes. Triclopyr is a selective systemic herbicide used to control woody and herbaceous broadleaf plants. It has little or no impact on grasses (e.g., arundo) but is very effective on tamarisk. Triclopyr controls target weeds by mimicking the plant hormone auxin, causing uncontrolled plant growth. It is most effective with cut-stump or basal bark treatments or with an effective surfactant. Offsite movement through surface or sub-surface runoff is a possibility with triclopyr acid, as it is relatively persistent and has only moderate rates of adsorption to soil particles.

Triclopyr can be found in two formulations: amine/salt (Garlon 3A) and ester (Garlon 4 and Pathfinder II). The ester formulation is not water-soluble and can take significantly longer to degrade. It can bind with the organic fraction of the water column and be transported to the sediments. Both the amine and ester formulations are relatively non-toxic to terrestrial vertebrates and invertebrates. However, the ester formulation can be extremely toxic to fish and aquatic invertebrates (Tu et al. 2001). Garlon 4 and Pathfinder II may be used in upland areas. Garlon 3A is recommended for use within 300 feet of water by the USFWS. In addition, USFWS recommends Garlon treatment to be completed by several weeks prior to winter rains to allow time for breakdown in the soil. Back to top.

Surfactants

Herbicides generally need to be applied with a surfactant. A surfactant is any compound that is added to an herbicide formulation or tank mix to facilitate the emulsifying, dispersing, spreading, wetting, or other properties of a liquid by modifying its surface characteristics (Lawrence 2002). Surfactants, also known as stickers/spreaders, are similar to detergents in their action, reducing water surface tension to allow wetting and penetration of the plant tissues. The surfactant helps to achieve optimum herbicide adsorption into and adherence from the herbicide on the plant. Surfactants may also improve an herbicide’s efficacy so that the concentration or total amount of herbicide required to achieve a given effect is reduced, sometimes as much as five- or ten-fold (TNC 2003). In this way, adding an appropriate surfactant can decrease the amount of herbicide applied and lower total costs for weed control (TNC 2003). All herbicide labels recommend surfactants and other additives to improve herbicide effectiveness. In some cases, the herbicide will already have the surfactant included, but in other cases, it will be necessary to buy one. Herbicide applicators should check the label prior to adding surfactant. Surfactants should be approved by the USEPA and regulatory agencies. Non-ionic surfactants, such as Agri-dex, are recommended by the USFWS. Back to top.