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Introducing Exotic Species to Fight Exotic Species Backfires

Swans It’s a clever idea to fight invasive species (like mute swans, pictured at left) by introducing other exotic species.  But perhaps too clever, according to a new report.

The Associated Press investigated the use of so-called “biological controls” across the country, and found troubling evidence that some imported insects brought in to fight invasive bugs are turning into pests that threaten native species.

Do you agree or disagree with the idea of using exotic species as a weapon against exotic species?

The argument in favor of these biological controls is that they can be less harmful than chemical pesticides.

But the Associated Press found that the federal government does little, if anything, to follow up on these introductions of biological control agents and find out if they are working as intended – or wreaking havoc on the ecosystem.

“A weevil released to attack a weed has veered off target and is gobbling up a native plant in Nebraska,” the AP reports. “A fly that was supposed to kill invasive moths is wiping out native moths in New England. And an insect introduced to combat a pesky weed led to a spike in the population of mice carrying a potentially deadly virus in Montana.”

“The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) has approved hundreds of biocontrol agents since the early 1970s…..(But) the agency does not know what happened to most of the biocontrol agents it approved for use.”

The question of what to do about invasive species in the Chesapeake Bay is a thorny one. Maryland has been using biological controls to contain an invasive flowering plant from Eurasia called purple loosestrife.  Scientists release tiny Eurasian beetles called Galerucella to devour the fast-growing plant.  But state officials say the Galerucella eats only this one kind of exotic plant -- and so therefore poses no threat to other plants or insects.  And there is no evidence that the introduction of this beetle has caused any harm.

Maryland wildlife biologists used poison to try to eliminate carnivorous Asian snakeheads when they were found in a Maryland pond a few years ago. But that failed to stop their escape into Potomac River tributaries, where they are now reproducing on their own.

An even more destructive invader, the European mute swan, has been gobbling up valuable underwater grasses in the Bay and driving away native birds. In response, Maryland has been conducting a campaign to spread oil on the eggs of the swans (smothering them) and take other lethal measures to control the population. 

The U.S. Fish and Wildlife service also works with state biologists to trap and kill south-American rat-like creatures called nutria that devour the roots of important marsh grasses in the Blackwater National Wildlife Refuge on Maryland's Eastern Shore.

What measures do you think are appropriate to control invasive species? Introducing other exotic species? Poisons?  Nothing?  Perhaps the only answer is public education to prevent introductions in the first place?

(Photo by Richard Baumann)


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I'm not a biologist/ecologist and certainly not informed enough to make a truly valid opinion, but using exotic species to control/contain another species bring to mind the parable of using a snake to control a rat problem and eventually ending up with a building full of elephants. Doesn't seem like a good idea.

Because that idea has worked so well in the past...

ur messin with nature now. not such a good idea!

A big can of worms that issue....

I'm with Michael....I'm pretty sure GOD knew what he was doing when he put things in their places! LEAVE WELL ENOUGH ALONE!

Relocate the swans and leave exotic species where they belong, not in our bay.

yea bad idea!!!

Introducing exotic or foreign species of animals, aquatic life or vegetation in many areas of the country has backfired as often as it has been successful. IMHO it's not worth the gamble.

It is not worth the risk.

Expanding on Paul Macom's comment, I recall hearing that tent caterpillars were first brought to this country by enterprising folk who thought they'd establish a textile industry to rival that from the silk worm.
-The best laid plans of....

We need to quit messing w/mother nature. What seems reasonable now harms us in the future. Look at "global warming"..........

Bio controls are a danger-Kudzu great example-purple loosestrife another. Then there are the fish, insects and other animals that endanger native species...

I live in an area seriously over run with asian ladybugs that were brought in to control something and black bears that were brought here from the Blue Ridge . .. . has it ever worked? really - are there any examples of importing an exotic plant or animal to control another that actually turned out to be a good idea? why do we keep trying?

I think as big a problem if not bigger is the resident geese population. I know in the upper reaches of the South River they are eating a pooping their way all around the river. At a pound of poop a day it is having a negative impact.

Good point, John. And the waste from all those resident geese produce a lot of bacteria that get into the river, as well as nitrogen pollution.

What solution do you propose?

recognizing the problem of the muted swans but believing we are smart enough to come up with a better answer than just shooting them.

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