Navigation Links
Biocontrol insect exacerbates invasive weed

Biocontrol agents, such as insects, are often released outside of their native ranges to control invasive plants. But scientists in Montana have found that through complex community interactions among deer mice, native plants and seeds, the presence of an introduced fly may exacerbate the effects of the invasive plant it was meant to control. The authors report their results in the September issue of the journal Ecological Applications.

Spotted knapweed, a flowering plant native to Eurasia, was first discovered in the United States in the late 1800s. This broad-leaved plant has an advantage over native plants because its natural enemies, including insects such as European gallflies, do not naturally exist in North America. Thought to have hitched a ride with hauls of alfalfa, knapweed is now widespread in western North America and has become a serious problem in the U.S. across Washington, Idaho, Wyoming and Montana and in Canada across Alberta and British Columbia.

As early as 1971, U.S. scientists began releasing gallflies in an effort to reduce populations of the invasive weed. Like all biocontrol agents, the gallflies were selected because of their specificity to their host plant, leaving little risk of direct harm to other plants.

Adult flies lay their eggs in the weed's flowers, and after the larvae hatch they induce the plant to grow tissue around the insect, encasing it and isolating it from the rest of the plant.

"The woody galls wall off the fly larvae from within flower head," says Dean Pearson, lead author on the study and a research ecologist with the U.S.D.A. Forest Service's Rocky Mountain Research station. "The larvae then overwinter in the seed heads for about nine months. When the plant devotes all that extra energy to producing these galls, it has less energy to produce seeds."

Scientists and managers expected that this seed deficiency would lead to limited knapweed population growth. An unanticipated side effect, however, involves the flies' furry neighbors. At the foot of the Sapphire Mountains in western Montana, omnivorous deer mice, whose diet usually consists of native seeds and insects, have also begun to prey on the introduced gallflies.

"These mice are generalists and very effective at exploiting a new resource," says Pearson. "They can tell which seed heads have the most larvae inside them, and that makes them very efficient." Pearson says that an average mouse can process 1200 larvae in one night. "A super mouse could go through a whole lot more than that," he adds.

At Pearson's grassland study site, spotted knapweed makes up more than half of the plant ground cover. The abundance of knapweed leads to lots of gallfly larvae, which serve as a food subsidy for the mice. Pearson and his coauthor, Ragan Callaway of the University of Montana, found that this extra nourishment bolsters mouse population size, increasing the numbers of hungry mice feeding on their original source of food: the seeds of native plants. As mouse consumption of native plant seeds increases, fewer native plants survive past the seed stage.

Pearson says that this exacerbation of the invasive species' impact has a lot to do with the effectiveness of the fly at controlling the knapweed.

"If the biocontrol agent is really effective, then it will eventually eat itself out of house and home, and the community interactions become less of an issue," Pearson says. He points out that even if the fly decimates 80 percent of the knapweed population, the 20 percent of seeds that are left to germinate are often enough to outcompete native plants.

The authors make the case that although biocontrol agents are carefully selected for specificity to their host plants, these restrictions do not prevent them from drastically altering the community food web, which can have far-reaching repercussions. Pearson hopes that a better understanding of food web ecology will lead to more effective tools for invasion control.

"Everything's interconnected," says Pearson. "We need to understand the ecology. If we can understand these complexities, we can attempt to minimize the side effects and maximize the effectiveness of our tools."


Contact: Christine Buckley
Ecological Society of America

Related biology news :

1. Tropical insects go the distance to inform rainforest conservation
2. Natural insecticide re-created in the lab
3. Japanese beetle may help fight hemlock-killing insect
4. Handbook of small grain insects available now
5. ESA celebrates 100 years of insect science journals
6. Tiny pest-eating insect fights fruit flies
7. Insect gut detects unhealthy meal
8. Insects giant leap reconstructed by founder of sociobiology
9. Ants and avalanches: Insects on coffee plants follow widespread natural tendency
10. Birds, bats and insects hold secrets for aerospace engineers
11. Insecticide combo delivers knockout punch
Post Your Comments:
(Date:5/9/2016)... UAE, May 9, 2016 Elevay ... comes to expanding freedom for high net worth professionals ... in today,s globally connected world, there is still no ... could ever duplicate sealing your deal with a firm ... passports by taking advantage of citizenship via investment programs ...
(Date:4/28/2016)... , April 28, 2016 First quarter ... (139.9), up 966% compared with the first quarter of 2015 ... totaled SEK 589.1 M (loss: 18.8) and the operating margin was ... (loss: 0.32) Cash flow from operations was SEK 249.9 ... 2016 revenue guidance is unchanged, SEK 7,000-8,500 M. The ...
(Date:4/19/2016)... 20, 2016 The new GEZE ... compact web-based "all-in-one" system solution for all door components. ... or the door interface with integration authorization management system, ... systems. The minimal dimensions of the access control and ... building installations offer considerable freedom of design with regard ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... 2016   Boston Biomedical , an industry ... to target cancer stemness pathways, announced that its ... Drug Designation from the U.S. Food and Drug ... including gastroesophageal junction (GEJ) cancer. Napabucasin is an ... cancer stemness pathways by targeting STAT3, and is ...
(Date:6/23/2016)... , June 23, 2016 Houston Methodist ... the Cy-Fair Sports Association to serve as their ... agreement, Houston Methodist Willowbrook will provide sponsorship support, ... connectivity with association coaches, volunteers, athletes and families. ... the Cy-Fair Sports Association and to bring Houston ...
(Date:6/23/2016)... 2016  The Biodesign Challenge (BDC), a university competition ... harness living systems and biotechnology, announced its winning teams ... New York City . The ... projects at MoMA,s Celeste Bartos Theater during the daylong ... senior curator of architecture and design, and Suzanne ...
(Date:6/23/2016)... ... June 23, 2016 , ... STACS DNA Inc., the sample tracking software ... State Crime Laboratory, has joined STACS DNA as a Field Application Specialist. , ... Tremblay, President and COO of STACS DNA. “In further expanding our capacity as a ...
Breaking Biology Technology: