Editor's Note: This article was published in our July 2007 issue.

by Jim Glendinning
Contributing Writer

The leaf beetle from Crete is coming soon to help control the spread of saltcedar in Bend National Park. That was the news delivered at a meeting at Sul Ross State University in Alpine on June 6.

Big Bend National Park personnel, including Superintendent Bill Wellman, and officials from the U.S. Department of Agriculture gave the sparse audience details of a new initiative to control one of the lesser-known problems affecting the Rio Grande: the spread of the saltcedar tree.  

Speakers described the tree’s introduction to the USA, its rapid spread across the western states and resultant ecological damage, and the progress of a biological control program using leaf beetles as the tool. The saltcedar or Tamarisk grows in Eurasia and Africa. Ten species were introduced to the USA in the latter part of the 19th century. Depending on the species, it was meant to serve variously as a decorative landscape plant, a defense against erosion along riverbanks, or a windbreak.

But, in little over 100 years it got out of control, spreading across more than two million acres in the western and southwestern states, and invading all major river systems including the Rio Grande. A US Department of Agriculture report (June 2007) called this “one of the worst ecological disasters in the recorded history of that region.” Locally, Big Bend National Park reports that “saltcedar occupies large areas of riparian floodplain and terraces along the Rio Grande and over 150 upland water sources.” Anyone who has fought their way through saltcedar to enter Santa Elena Canyon will know what they mean. Boquillas Canyon is another infested area.

The small shrubby tree propagates quickly and spreads extensively. Saltcedars produce thousands of flowers in spring and summer. The seeds are very small and can float on the wind or on water for long distances. One single mature plant can produce 500,000 seeds in one year. It takes only one season for a seedling to develop into a mature, flowering plant.

Once established, the saltcedar is a tenacious tenant. Its root system is substantial with a tap root sometime reaching 15 feet deep and secondary surface roots which soak up rainfall. It tolerates drought, heat, cold, salinity, fire and flooding. But this is not the worst part.

The worst part is its effect on existing native plant species, local wildlife and the physical environment. Since it exudes salt from its leaves, native grasses and shrubs are exposed to the soil’s salinity and die. The saltcedar also displaces larger trees like cottonwoods and willows. It is too small to be a food source for birds. Larger animals such as deer or bighorn sheep avoid water sources close to saltcedars.

When saltcedar thickets along a river course proliferate, the river can lose its definition. Clumps of saltcedar obstructing the river bed force flood waters to alter course beyond the existing river banks. Upstream from Candelaria is an example of this. On top of all these complaints, the species’ appetite for water makes it a special menace in a drought-prone environment.

The introduction of exotic plant species to the US is nothing new. Biological methods of control are not new either. More than 1,000 projects around the world over 150 years have used the natural enemies of invasive exotic plants to control them.

Research into saltcedar biological control by the US Department of Agriculture using leaf beetles has been on-going since 1986. Entomologist Dr. Jack DeLoach of USDA Agricultural Research Service described at the SRSU meeting how planned biological control of saltcedar has been tested during the past 14 years: in 1991 the first beetle was introduced to the USA; in 1999 was the first release in field cages in six states (the beetles in south Texas did not survive the winter), and in 2001 there was beetle release to five open-field sites in five states including Texas. At the Texas research site at Big Spring, the effects of beetle defoliation on salt cedar are being studied and the results are good.

The use of biological agents to control the BBNP infestation would be a quick, low-cost means in comparison with other methods used to-date. These include bulldozing and use of herbicides which are slow and labor-intensive, and aerial spraying which is expensive and risks killing native plants. Using the salt cedar’s natural enemy offers the good possibility of a quicker, more effective result.

One question is which beetle to use. Research by Dr. DeLoach took him to Uzbekistan, China, Crete and elsewhere looking for leaf beetles. Tests are currently underway between Candelaria and Presidio to determine which is better suited to the climate and latitude of the Rio Grande. Right now it looks as if the Crete beetle might be the one for Big Bend.

Once a leaf beetle has found a suitable climate zone to settle in, it can be quickly effective. Near Moab, Utah, three releases of 10,000 beetles defoliated 11 miles of continuous saltcedars within 12 months. At Big Spring, TX the test release of the Crete beetle defoliated a 25-acre stand of saltcedar, and the amount is increasing ten-fold per year.

The small beetle is a big eater, but fortunately his appetite doesn’t extend to native species. This removes one of the main worries of local people from birders to ranchers.

Surprisingly, there was no attendance at the SRSU meeting by these two groups or by environmentalists who might have quizzed the scientists about possible negative effects of the program. 

Jim Glendinning was raised in rural southern Scotland and schooled at Fettes College, Edinburgh and  Lincoln College, Oxford. Glendinning has worked a variety of jobs in the USA and Britain: restaurant owner, tour manager, transatlantic charter flight operator, tea-room owner, tour guide, and director of a national student travel company. Between jobs he travels frequently, having been to 120 countries so far. Glendinning has lived in Alpine since 1991 and writes regularly for local papers, updates his guide book and takes tour groups to Chihuahua’s Copper Canyon.

In Boquillas Canyon along the Rio Grande in Big Bend National Park, the exotic Tamarisk, or saltcedar, has invaded and proliferated to become dense enough to almost completely hide this person (center). Saltcedar adversely affects the native vegetation, soil, and wildlife, greatly altering the ecosystem. (Joe Sirotnak, photo)

BBNP and USDA are proceeding optimistically with the project. It takes time, however, not least with public meetings, liaising with Mexican authorities and between the various federal agencies. Progress is being made and a tamarisk biological control program in BBNP is planned to start by February 2008, according to Vidal Davila, Jr., Chief of Science and Resource Management at BBNP. Thus a quarter-inch-long, olive-colored leaf beetle may be the undoing of the tamarisk. The scientists are not looking for a knock-out blow, however. The aim is to bring the damage level down to manageable size, giving continuing work for the Crete beetle (above): maintaining a balance.
(James Tracy, USDA, photo)