SALT CEDAR LEAF BEETLE: Is this little bug being too efficient?
Image: BOB RICHARD/US ANIMAL AND PLANT HEALTH INSPECTION SERVICE
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A foreign beetle imported to attack invasive trees in the U.S. Southwest may have brought its own culinary agenda. Researchers in Utah and Arizona are sounding the alarm about salt cedar leaf beetles, which were imported from Kazakhstan several years ago to control invasive tamarisk trees.
"Now that the beetle is spreading to large areas, we need to start looking for unexpected consequences of defoliation and death of the tamarisk," says Philip Dennison, a geographer at The University of Utah and lead author of a study warning of the unintended risks published this month in the online edition of the journal Remote Sensing of Environment.
Tamarisk trees, native to Europe and Asia, were first planted in the U.S. in the early 1800s as ornamentals and to stabilize soil, especially on riverbanks. The trees took off, and now dominate 1.6 million acres (650,000 hectares) of mostly riverside habitat throughout the Southwest. Dense tamarisk stands have crowded out native trees like cottonwoods and willows. And tamarisk gets a bad rap for being thirsty enough to drop water tables and dewater small streams—although the new research says the rep may be undeserved. Tamarisk was first identified as a pest around 1900, and biologists since the 1940s have implemented various control strategies, including herbicides, manual removal, and defoliation by goats and beetles. Total cost estimates approach $100 million for the decades-long efforts.
Beginning in 2001 biologists in nearly all southwestern states—with input and funding from the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS)—released the beetles in tamarisk thickets.
The program has been "spectacularly successful, one of the most successful biological control projects ever in the U.S.," says Jack Deloach, an entomologist with the U.S. Department of Agriculture's (USDA) research arm, the Agricultural Research Service.
But Dennison and his co-authors are now proposing that officials put on the brakes, based on satellite monitoring in 2006 and 2007 of 56 beetle-treated areas in southern Utah. The researchers report that beetles have been dutifully stripping the tamarisk of their needles but that some of the immediate effects are worrisome.
As it turns out, tamarisk trees have a silver lining, Dennison says. Their sprawling branches, which are covered with long, pliable needlelike leaves, provide coveted cover for native birds. Among them the endangered willow flycatcher, which routinely nests in the tamarisk thickets that replaced the willow trees there. Salt cedar beetles were originally kept out of Arizona and New Mexico to protect the flycatcher, but researchers report that the beetles are now creeping from Utah's Virgin River into flycatcher habitat in southern Utah and northern Arizona. The Center for Biological Diversity (CBD), a Tucson, Ariz.–based conservation group, has filed a notice of intent to sue the USDA and APHIS to halt the beetle program, charging that the bugs have gotten out of hand and are threatening the endangered birds.
Nate Ament, a restoration ecologist with the nonprofit Tamarisk Coalition in Grand Junction, Colo., says the greatest risk to streamside ecosystems comes in tamarisk's wake. The new satellite data show tamarisk-related water loss is lower than previously believed. If tamarisk trees are killed off by the beetles, newer weedy arrivals—like Russian knapweed, Russian olive and pepperweed—could hammer the water supply even more.
"We really emphasize revegetation with native trees as a crucial component of the restoration process," Ament says.
On that point, all sides agree. The CBD's Robin Silver says one of the aims of the suit is to prompt revegetation with native trees, like willows, in places where the tamarisk might die off.
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8 Comments
Add CommentNo group of minds can accurately determine the effects of an introduced bio-control. There are far too many variables, compounded by groups seeking benefit.
Reply | Report Abuse | Link to thisCan anyone come up with a list of introductions that did not cause problems? Stop moving isolated species from one environment to another.
Trying to eradicate trees is the most stupid thing I have ever heard. All life depends on inputs like food. Basic food is created by photosynthesis. Plants do most of this work on land. We have already reduced global plant cover by about 25%. In short we have reduced food supply by that amount.
Evolution is at work, it has worked for millions of years, we have enjoyed the benefits of living on a fertile self sustaining planet powered by its sun. All we have done is degrade our soils, de-forest our planet, contaminate our air and water. We claim we can think! Evolution will take care of all the problems we have created allow it to get on with the job.
totally on it = email i good@gmx.co.uk - you talk sense -
Reply | Report Abuse | Link to thisthat was @scienterrific earthling btw:)
Reply | Report Abuse | Link to thisbiguP - number 1 comment btw
:)
I dunno - we got Globalization, now.
Reply | Report Abuse | Link to thisMi casa es su casa.
Su problema es mi problema.
Best we get used to exotic plants, bugs & diseases.
If you haven't spent any time around Tamarisk trees you don't know much about them. I have spent years on private property in AZ with this tree. They consume springs and water holes, destroying native habitat and stressing wildlife. The bird, a Willow Fly Catcher, will move back to reemerging native species which do grow fairly fast.
Reply | Report Abuse | Link to thisTrees normally control their spread by emitting chemicals that prevent the same species from growing nearby. You can clearly see the effect on sloping ground, the one at the top does well the one lower down barely survives. I made a mistake planting 2 robinas 2 meters apart on a slope, the top one is huge, the lower one is almost the same size as when I planted it.
Reply | Report Abuse | Link to thisPerhaps Tamarisk trees are like humans an invasive species that can not control its numbers. However would you introduce a new species to control an earlier introduced species?
Remember the people who introduced the species did so for a reason, and now you have a problem, introduce another species to control this one and then yet another to control the new introduction.
In Australia we introduced dozens of species, almost all are a problem. examples: rabbits, flies, goats, sheep, foxes, Indian minas, cane toads, privets, it just goes on and on.
Study the life cycle of the truant species, use its weakness to control its population, as we must our own - our weakness greed.
scientif earth t'ing ling
Reply | Report Abuse | Link to thisrespec'
awesome again
one seas da god p article in yr last line above - beauty - always is easier to sea truth as a dual - a comment on a comment on a etc seeen in contrast -
well played
true player
check mate no stale
awesome
JAH warn us we have a weakness one pressumes
:)
I have lived in Moab my entire life and have seen the damage that the tamarisk are doing to the native plants that grow natrually along the river. They choke them out and are really out of control. Also no matter if the tamarisk are dead or alive they are going to be a fire hazard because of the oils that are in them.
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