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The once open beaches and cottonwood galleries along the Colorado River and many other western rivers have all but disappeared. Instead densely crowded stands of Tamarisk, interspersed with Russian Olive, have replaced sandy beaches and once open stands of native plants. The takeover has been so complete along vast stretches of the Colorado River that wildlife habitat has been degraded, recreational beaches shrunk and, millions of acre-feet of water lost through tamarisk consumption. This invasion of exotic plants, compounded with global warming in the form of drought, and escalating populations are putting huge pressures on western water supplies.

Tamarisk was introduced from Eurasia in the early 1900’s for its beauty and ability to control river bank erosion. Introduced in California it galloped up the Colorado River basin, crowding out native trees and plants and becoming almost a monoculture in places. Tamarisk has deep roots, up to 100 feet, and can gulp large quantities of water. Coupled with its propensity to create dense stands it uses much more water than the original natives. California has become so concerned by this water loss that the state passed a law (Assembly Bill 984) that directs California to work with other states to develop a comprehensive plan for tamarisk control and revegetation for the entire Colorado River system. Needless to say tamarisk has been hard on the whole riparian system.

The Grand Canyon Trust has been involved in a planning process with many others (federal, state, local, private individuals, non profits) for the past year and a half working on a document that would outline a strategy for controlling Tamarisk and Russian Olives (and other invasive woody species) as well as native revegetation along the Colorado River and its tributaries in southeastern Utah. The Tamarisk Coalition, from Grand Junction, Colorado, asked the Grand Canyon Trust to organize the first meetings. We gladly agreed to help launch this effort to:

• Learn if there was interest in creating a regional strategy, and then
• To shepherd the process of monthly meetings,
• Help raise money to pay for the consulting and writing of the plan by the Tamarisk Coalition, and
• Gather information from this knowledgeable group that would insure a vision well tailored to the people and place.

The group rapidly coalesced and started work. One of the compelling opportunities was a bill that was being sped through the Congress, called the "Salt Cedar and Russian Olive Control Demonstration Act" (HR 2720). HR 2720, has now passed and is referenced as Public Law 109-320, it authorizes funding for demonstration projects in regions like ours. The hope of funding has been incentive for the SEUTP group to complete the Strategic Plan. Our group, named the South East Utah Tamarisk Partnership (SEUTP), has worked to meet all of the criteria in the legislation. We have also provided a catalogue of techniques for removal with our own recommendations of preferred methods, project areas, and a strong emphasis on monitoring a Eurasian beetle that shows real promise for controlling tamarisk. Our study also highlights other control techniques, and contains maps that show the location and density of tamarisk in our study area.

Enter the Beetle

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While the partnership was studiously meeting and crafting careful statements about our mission, meeting in various subcommittees, arguing over best practices of removal and control, Grand County’s Weed Supervisor took the matter out of our hands: he released the tamarisk beetle (Diorhabda elongata) into the wild where millions of them were quietly going to work along the river banks.

The tamarisk leaf beetle has been imported from Fukang, China. Tamarisk has been so difficult to remove with cutting and herbicide applications that biologists began searching for a biological agent that might check their spread and not become its own biological disaster. APHIS (Animal and Plant Health Inspection Service) has been studying the beetle rigorously for 20 years. The beetle feeds only on tamarisk and so far it has shown no ability to cross over and eat other species. Reassured by many years of study, the Grand County Weed Agent collected beetles from one of the study areas (Delta, Utah) and released them onto privately owned sites along the Colorado River. Because of the release on private not Federal or State lands, the releases could legally go ahead, and that is exactly what the Grand County Weed Supervisor did. He also released more beetles than other regions had and did it repeatedly at the same locations. Because of his strategy the beetles have dramatically prospered.

This was an unheralded local release. The first season the beetles defoliated only a few tamarisk. After one year 2 acres were defoliated. In year 2 the insect populations were fully established and tamarisk was totally defoliated (though not killed) on over 10 miles of the Colorado River. Year 3 was like watching a brush fire brown out several miles of riverbank a week. Suddenly the whole Colorado River corridor from Moab up nearly to the Colorado state line and downstream 70 miles to the Green River had been defoliated; those once green tamarisk have been turned into brown skeletons. Within a week the 800 acre Matheson Wetland Preserve in Moab turned completely brown. It is breathtaking. It is also sobering. This year, the 4th year, because of a cooler spring, the beetles had a later start and tamarisk did not show signs of defoliation until the end of June. But it has again been a dramatic and rapid brown out along the river, within a week or two huge strips along the river have turned brown. We are also seeing the first die out of tamarisk, from the area they were first introduced.

Last fall the beetles went into diapause, a form of dormancy. Very quickly the tamarisk shot out new leaves, although certainly not as many as previously. The skeletonized trees instantaneously grew a cloak of green foliage. It was astonishing. This will be the pattern for a few years, while gradually the root is weakened and eventually the tamarisk will die.

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So while we were primarily focused on removal techniques early on in SEUTP, with the success of the beetles we are shifting our focus to questions about how to manage the beetles and the brown out of the tamarisk. As yet we don’t know if the beetle will actually kill the tamarisk over a period of years, nor how complete any control will be. There are unanswered questions about the effect of different removal techniques, which can either encourage the return of natives or create a vast seed bed for the next cycle of invasive non-natives. These are huge questions. Currently we are applying for research grants that will inform on the ground removal and revegetation projects.

Because of our location in the epicenter of the tamarisk brown out we are in a very good position to watch and research the tamarisk beetle. What is happening here will soon spread throughout the upper basin of the Colorado River and beyond. Unfortunately the beetles only work north of the Arizona-Utah border. Further south and the beetles emerge from winter before the tamarisk have leafed out and the beetles die. Arizona, New Mexico, Texas, and California will need to decide if they want to release beetles, which I’ve heard have been found, that work in their climate.

Questions we have:

• Will the beetles behave as expected, or will there be unintended consequences?
• What removal techniques are most helpful for the reintroduction of native plants?
• Which techniques encourage noxious weeds?
• Is it possible that doing nothing with the browned out tamarisk may be a good technique in the long run?
• Will removing the dead tamarisk be important for revegetation?
• Are the dead tamarisk more of a fire hazard than the green ones?
• What are the best and most cost effective methods for revegetation?
• Will herbicide still be needed to kill the tamarisk?

Included in this website is a Fact Sheet (Most Frequently Asked Questions) put out by the group to answer questions. You can go to tamariskcoalition.org for more information about tamarisk. The SEUTP Strategic Plan is also available on this website.

The SEUTP is transitioning from a group working to create a strategic plan to one applying for funding and completing projects. It has been exciting to witness some large scale removal projects (200 acres) initiated by the BLM but augmented by the help of other SEUTP members. We are excited to see the re-emergence of some important beaches along the Colorado River. Revegetation is planned along some of the BLM control areas for this fall ‘08, funding for this was awarded to the SEUTP coalition. Different treatments are being monitored and data being collected monthly.

We have much to learn and a huge area of tamarisk and Russian olive to control. We will be at this for a very long time.