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Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
- 10 April 2014 11:44 am , Vol. 344 , #6180
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Insects No Match for Invasive Weeds
9 August 2001 7:00 pm
MADISON, WISCONSIN--When plants such as kudzu creep across the landscape, resource managers often release exotic insects to stem the invasion. But despite consuming the plants, most biocontrol insects fail to stop their spread. Now field studies suggest that the insects are simply overwhelmed. The results, presented here on 8 August at the annual meeting of the Ecological Society of America, could help researchers come up with better tests for picking biocontrol agents.
Before release, biocontrol insects are usually tested to make sure they eat the invader and are likely to establish themselves in the invaded habitat. But few are tested in the field to see if they'll beat back plant populations, says ecologist Amanda Stanley of the University of Washington, Seattle. For instance, two species of seedhead gallflies were imported about 30 years ago from Russia to control spotted knapweed, another Russian import that is taking over grasslands and savannas across the Western United States and Canada. Although the gallflies breed easily in the region and eat the seeds of spotted knapweed, the plant continues to spread unchecked.
To find out why, Stanley looked at how gallflies and spotted knapweed interact in the field. They caged off some plants to keep gallflies out and compared their fates to those in plots where gallflies had free access. Gallflies ate most of the spotted knapweed seed, cutting seedling density by 50% in areas exposed to gallflies. But the same number of seedlings survive to adulthood with or without the gallflies. Apparently, gallflies can't keep spotted knapweed populations down because the plants produce so many seeds that plenty escape the ravenous insects.
"I thought this was a fascinating study," says ecologist Tim Craig of the University of Minnesota, Duluth. The work also shows that more studies should be conducted prior to release that address whether biocontrol agents actually cut plant populations, he says.