November 3, 2006
Herbicides are used widely to rid watersheds of salt cedars but aerial attacks are only part of the battle plan...
By Bobby Horecka
With water resources stretched ever thinner as the population grows across Texas, the last thing you want sapping up your surface water is a sorry old salt cedar.
Yet the pesky perennial remains a mainstay in many parts of West Texas, particularly along riverbeds on some of the state's most precious watersheds.
But what if the science could overwhelm the unwanted bush and return those waters to those areas most in need?
That's exactly what rangeland specialist Allan McGinty envisioned when he began work on the Upper Colorado River in early 2001, and while this year's drought offers poor indication of the progress made, McGinty is certain the work will eventually pay off.
Contract helicopters took to the air in early September to wrap up herbicide applications of the current Environmental Protection Agency Section 19 grant McGinty secured to restore water levels along the Upper Colorado. That work is the culmination of nearly the last decade's research into watershed restoration.
Spraying along Lake Thomas began in 2005, covering some 1,800 acres of salt cedar-infested lands with 75 percent of the landowners' participation.
But it wasn't herbicides alone that have made such an impact on the project, McGinty said. For the rest, he credits the work of another fellow researcher, insect specialist Jack DeLoach with the U.S. Department of Agriculture.
DeLoach's research has focused on the workings of a leaf eating beetle that preys on salt cedar. Considering salt cedar is itself an imported species, brought in as an ornamental in the 1800s from Eurasia and later used for erosion control in the 1940s, introducing a new species to the area was a careful operation.
But DeLoach's research revealed that the beetle fed only on the salt cedar, leaving desirable hardwoods alone. When the scrub trees died, so did the beetles, and the first controlled releases of the insect got under way.
"The beetle isn't a silver bullet," McGinty said. "But neither is the herbicide. Together, however, they're an extremely effective tool."
McGinty said the herbicides are about 85 percent effective, meaning roughly 15 percent will remain alive. "If you know anything about salt cedar, the 15 percent will have you right back where you started from in 10-15 years," he said.
But releasing the beetles along with spraying, helps control that resistant group, and since the beetles feed on salt cedar alone, they're around just as long as there's something to eat. For an area infested with the trees, the bugs have proven quite prolific, McGinty added. Just 36 of the beetles were released at the first site near Big Spring. Now they number in the thousands, by conservative estimates, and are dutifully doing their jobs.
With the current $12.2 million grant, McGinty says the work should be finished by early 2007, covering nearly 220 miles of land from Lake Spence to Lake Ivey and now including 95 percent landowner participation.
With progress seen in the decreasing salt cedar numbers, McGinty said his sights are now setting farther downstream _ Lakes Buchanan and Travis. Although salt cedars aren't there now, McGinty is concerned, particularly given current drought conditions.
Lake Buchanan, for instance, has receded 19 feet over the last few dry months. The last time lake levels got that low in the late 1990s, McGinty said several salt cedar sprigs, carried by previous floods, began growing in the dried lakebed.
When the lake refilled, the salt cedars were drowned out where they stood, and Buchanan returned to its salt cedar-free status, McGinty said, having surveyed the area just a few weeks ago.
But if conditions continue as they are, Extension specialists worry the invasive tree could return. Lake Ivey, one of the current project areas, had no salt cedars in 1995, McGinty said. Today the lake is nearly surrounded by them.
And given larger people population numbers the farther downstream one travels, securing needed easements for the work could prove problematic.
Removal of the trees early is crucial, McGinty said. Not only can one tree drain the land of thousands of gallons of water per year, the plants also replicate quickly, choking out other vegetation in course thickets.
Thus far, McGinty has successfully landed two EPA grants for the project, working closely with Ben Brooks of the State Soil and Water Conservation Board, as well as local resources with the Texas Cooperative Extension Service.