Reprinted with permission of
Lubbock Avalanche
Journal
Battle of the Bug
Beetles recruited in fight to control water-guzzling tree
BY ELLIOTT BLACKBURN
AVALANCHE-JOURNAL
Groundwater experts across the country are putting a lot of faith in a little beetle.
The salt-cedar leaf beetle, a tiny winged insect native to parts of Asia and the Mediterranean, has been studied for the past decade as a way to battle back against trees guzzling billions of gallons of Western groundwater.
There are no hard numbers, but some estimate an acre of tamarisk, also known as salt cedar, can remove between 300,000 and 1.6 million gallons of water in a summer growing season in Texas. The Canadian River Municipal Water Authority, which supplies 80 percent of Lubbock's water, is battling 11,000 acres of the tree around Lake Meredith.
Fire won't stop salt cedar. Bulldozing just makes it mad, one water manager said. Herbicide, the most effective manmade solution, can cost millions. But docile, diminutive Diorhabda elongata dines exclusively on the plant.
"There's just not enough money at Fort Knox to keep doing this," Okla Thornton, manager of natural resources for the Colorado River Municipal Water District, said of salt cedar control costs. "We're going to get one shot at this, and if biocontrol isn't the silver bullet when we knock it back, we're in trouble."
Salt cedar has dogged water district managers in the Southwest for years. The Asian ornamental plant was installed along riverbeds and railroad tracks in the early 19th century to curb erosion, but quickly proved to be its own potent environmental threat.
Trees can gulp up to 200 gallons of groundwater a day from water as deep as 100 feet during the growing season, and the tree's mineralized, thin leaves deposit salt and ruin the earth beneath its branches.
It spreads farther and taps deeper water tables than native cottonwoods and willows, boasting a greater tolerance for salty soils and no native enemies, said Fred Nibling, a researcher for the U.S. Bureau of Reclamation.
That's a big problem in arid areas like West Texas, where groundwater is becoming an important element of securing long-term water supplies. The Colorado River Municipal Water District is battling 20,000 to 30,000 acres of the tree in a 26-county area around Odessa and Big Spring, Thornton said.
"Its impact on water resources and water quality probably is almost impossible to define," Thornton said.
Aerial herbicide sprays are the only effective manmade weapon, district managers said, but can cost more than $200 an acre to spray. Because salt cedar grow thick around streams, there are environmental concerns about how safe some areas are for spray.
So for the last decade, sites around the West have nurtured and studied the salt cedar leaf beetle, hoping that the tiny green insect will prove a cost-effective way to keep the tree population in check.
The process to introduce the insect has been about as long and complicated as it might take to develop a new herbicide, said Raymond Carruthers, an invasive-species expert working with the U.S. Department of Agriculture's Agricultural Research Science office. An estimated $2 million to $3 million from several different federal agencies has been invested throughout the past 10 years in the project, but once the beetles get started, there's no cost to maintain them, Carruthers said.
Small colonies of the beetle are vulnerable to weather and other insects. Northern beetles brought to Lake J.B. Thomas, near Big Spring, starved to death when the shorter days confused the insects and they began hibernating instead of eating.
The insects have been carefully studied to ensure they don't develop a taste for any crops or native plants, growing and munching tamarisk in quarantined labs. Researchers faced even more hurdles when an endangered bird was found nesting in salt cedar stands.
But the beetle is producing big results in areas like Nevada, where the population has swept through a 100-mile area of salt cedar, Carruthers said.
"It's just like an explosion of these beetles that's stripped all of these salt cedar of anything green," Carruthers said. "It took a thousand beetles to get it started, and now there are literally billions of them."
The beetles are spreading across a small section of a private ranch outside of Big Spring under the watchful eye of USDA and other local and federal researchers. If they continue to do well, they'll be taken to Fort Stockton in a few years, and ultimately sent anywhere there's salt cedar in Texas, said Texas A&M Agriculture Extension entomologist Allen Knutson.
A group of beetles on federal land where the Canadian River enters Lake Meredith is spreading slowly, extension entomologist Gerald Michels Jr. said.
Texas researchers doubted the beetle will replace herbicide. It takes thousands of the beetles, and a couple of years, to eliminate a salt cedar tree.
"I don't think they'll ever be able to attack a growing stand of adult trees and gnaw them down to the ground," said John Williams, a manager of natural resources for the Canadian River Municipal Water Authority.
But Williams and other experts hope the insects will be a cheap, effective tool to keep salt cedars in check.
"We're always going to have salt cedar with us - there's no way to get rid of it," said Jeremy Hudgeons, an A&M masters student tracking the bugs in West Texas. "But (we're) getting a way to manage it."