Saturday, August 13, 2005

ENV: Introduced bug to counter invasive

As someone who works on occasion with the dynamics of invasive species, i always get a cold chill when reading about the introduction of some predaceous species to counter the spread of another invasive. In this case it's the Salt-cedar Beetle. There are several species of Salt-cedar loose in the west (despite the "research" cited below), and are particularly nasty denizens of what is now wasteland in west Texas. I got to know it well as it was the nesting substrate for the isolated race of White-winged Doves i worked on in the Presidio valley. Much of it was originally brought in as windbreak, but now it adds chlorides to groundwater and has made some stretches of western rivers uninhabitable by much of anything native. So getting rid of that icky plant is a good thing.

But you know, if they've miscalculated on the adaptability of the beetle -- well, there's precious little other vegegtation left out that way. Now, biologists working in this field are much more aware of the consequences of their actions in doing this these days -- but, pressure to reclaim lost territory, and the thrill of being an agricultural hero . . . well, it could be a slippery slope. And i'm particularly spooked by the casual joking quoted in this article. Once again Mexico seems to have its stuff together better than we do. I hope this if for real, but all my fingers are crossed.

Salt cedar foes put hopes in saltcedar beetles
John MacCormack, San Antonio Express-News, Staff Writer Web Posted: 08/11/2005 12:00 AM CDT

"Two adults, four (large larva), five leafhoppers and 98 percent defoliated," the technician said as colleagues below recorded the data on a special form that included codes for things like stink bugs and moth larva.

Welcome to the front line of the war in Texas on salt cedar, the plant pest equivalent of fire ants, German cockroaches and Norway rats all rolled into one spindly but highly successful foreign invader.

Stray lady bugs, ants and leafhoppers aside, the only important critters being counted around Big Spring these days are small olive-colored beetles recruited from the Mediterranean because of their singular appetite for salt cedar.

At a test site outside Big Spring run by research scientists from the U.S. Agriculture Department, the beetles carefully are being acclimated to life in Texas, which has more than its share of salt cedar.

"Last summer you could come out here and all you'd see was green. Now we can find hundreds of adults on a single tree, and trees that are defoliated. It feels pretty good," said Tracy, 43, who began working on the multiagency project in 1992.

Salt cedar, also known as tamarisk, was introduced to the United States from Asia as an ornamental plant early in the 19th century. It later was spread via government programs to contain stream erosion and now overruns roughly 2 million acres in the West.

"In the western half of Texas, it's basically taking over all of the riparian (river) systems. It comes in and chokes out native vegetation. And when it gets dense, it takes so much water, it pushes the water tables down and reduces river flows," said Charles Hart, a range specialist with the Texas Cooperative Extension.

Hart has been involved in a long-term spraying program covering nearly 400 miles of the Pecos River to control the plant, but is the first to admit that spraying alone is not the solution.

"The chemical is not a silver bullet. You can never kill 100 percent of what you treat," he said.

With no native enemies in the United States, salt cedar's spread across the West has gone nearly unchecked. Along vast stretches of the Rio Grande west of Presidio, it has pushed out native willows and cottonwood, and stretches from bank to bank.

But after two decades of research and wandering around Asia in search of salt cedar's natural foes, scientists believe they have found, if not the magic bullet, at least an effective means of control.

Last week, tens of thousands of saltcedar beetles distantly related to those being raised at Big Spring were released at 24 sites in Colorado, Idaho, Kansas, Wyoming, Montana, Oregon and South Dakota.

In Texas, the project has lagged, in part because of the difficulty in finding the beetle that feels perfectly at home here. All the latest signs are that a harmonious match has been found.

Feeding and breeding with abandon at the Big Spring test site are hordes of quarter-inch-long beetles native to Crete.

"In April of last year, we released 38 beetles at Big Spring. By September, they had increased to a few thousand and defoliated a big tree. They over-wintered well, and so far this summer they have defoliated all of the trees in the first row," said Jack DeLoach, 73, a federal entomologist who has been with the program since its inception in 1986.

"I think these beetles will be successful. If we can get them spreading rapidly for a couple of years, they'll be all over West Texas," he said.

DeLoach, who made five trips to China, Kazakhstan, Israel, France and Turkmenistan in search of salt cedar-eating insects, believes Texas is only a year or two away from seeing widespread beetle distribution.

One remaining hurdle is fine-tuning the matches between the various strains of Asian beetles and the differing climes and latitudes in Texas. The beetles DeLoach brought from China are doing very well in Nevada and parts north, but they bombed in Texas.

And while the beetles from Crete are doing just dandy in Big Spring, scientists doubt they will thrive several hundred miles to the south along the Mexican border.

"We may have to try a Tunisian beetle, or beetles from Uzbekistan down there," said DeLoach. Tunisian beetles are now being tested in Kingsville, located at approximately the same latitude as the Rio Grande in West Texas.

And, said DeLoach, there also remains a diplomatic hurdle.

The Mexican government is concerned about the release of beetles along the international border. Their hesitancy is because the saltcedar beetles occasionally eat athel, a close Asian relative of salt cedar that is used as a shade tree and windbreak in northern Mexico.

All tests so far show that the Crete beetles vastly prefer salt cedar to athel, and so far have shown no appetite for any native Texas plants.

"A real big concern is that they didn't eat anything else — bluebonnets or cotton for example," joked Allen Knutson, 54, an entomologist from Texas A&M, a partner in the project.

Knutson said he regularly fields requests for beetles from landowners plagued by salt cedar, but has to tell them to sit tight.

"There is a tremendous amount of interest. Anyone who has salt cedar wants them. It's a control program that is self-perpetuating and essentially has no cost," he said.

Technicians Tracy and Tom Robbins come to Big Spring from Temple almost weekly to oversee surveys of 144 numbered branches, as well as quick counts of beetles on another 70 trees scattered hundreds of yards from the original release point.

And lately, the beetle counters working among the horned toads, cow pies and mocking birds have been heartened.

Many of the beetles released recently in northern states are descendents of those collected years ago by DeLoach in Asia. On one trip he collaborated with a Chinese specialist who had salt cedar problems of his own.

"Professor Liu Ming Ting had been working his whole career trying to cultivate salt cedar in Western China," said DeLoach, whose team roamed the Asian countryside looking for salt cedar trees.

One bug they found eating salt cedar was a yellow-green beetle that was no stranger to their Chinese host.

"This beetle was well-known to professor Liu Ming Ting. It was causing so much damage to their tamarisk plantation that they were having to spray for it. And that's just what we were looking for," DeLoach recalled with a chuckle.

Saltcedar Leaf Beetle Diorhabda elongata
Native habitat: Central Asia and parts of the Mediterranean Sea region.
The beetles used near Big Spring are from Crete.
Size: Adults are about a quarter-inch long and about an eighth of an inch wide.
Life span: Adults live about 18 days and females can mate several times while alive, laying 30 eggs each time.
Food: Both the adults are larvae can be used to defoliate salt cedar.

Salt cedar Tamarix ramosissima
Native habitat: Native of Eurasia and Africa introduced in the U.S. as an ornamental species in the early 1800s. Grows in streams, waterways, bottomlands, banks and drainage washes of natural and artificial bodies of water and moist rangelands and pastures.
Invasiveness: Long taproot allows it to intercept deep water tables; due to its high consumption of water, it decreases surface water flow. Increases soil salinity, making it difficult for native plants to grow. Increases effects of fires and floods.

Sources: U.S. Army Corps of Engineers, Engineer Research and Development Center, National Park Service and Texas Synergy project Web site
Compiled by News Researcher Julie Domel


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