Researchers weed out ineffective biocontrol agents

Apr 18, 2013
This is a photo of Larinus minutus, a weevil introduced to combat the invasive diffuse knapweed in western North America. The effectiveness of the weevil and other biological agents may be reduced when species combinations work against each other. Credit: UBC

'Keep it simple' is a good rule of thumb when designing biocontrol programs to combat weeds and invasive plants, according to a meta-analysis of studies by UBC biodiversity experts.

Biocontrol programs use an invasive plant's (insects and ) to reduce its population. Most biocontrol programs combine many different enemies – typically about three different , but sometimes as many as 25 – with the hope that at least one will prove effective.

But more isn't necessarily better. Some combinations of enemy species can actually end up competing or interfering with each other, instead of attacking the weed.

"It's important to get the right combination of , as testing species is costly and time-consuming, and no amount of testing can eliminate the risk that something unexpected will occur with the introduction of a new species," says Andrea Stephens, lead author on the paper published in the Proceedings of the Royal Society B this week.

Until now, biocontrol managers have chosen weed enemies to release based on the individual effect of each species in isolation, with little thought to overall combinations.

"Our study suggests that this approach can lead to ineffective biocontrol, because the interactions between the released enemies can reduce the overall effectiveness of biocontrol," says Diane Srivastava, author on the paper and professor in UBC's Biodiversity Research Centre.

Of the 75 combinations the researchers investigated, about a quarter appeared to have a smaller combined impact than expected. The researchers suggest simple species combination rules could improve the effectiveness of biocontrol programs.

The study recommends avoiding combinations of species that attack the same part of the plant at the same time, as well as assessing the impact of species attacking reproductive structures.

"In most cases damage from different species of insects was independent," says Judith Myers, Professor Emerita and author on the paper. "But insect species feeding on the seeds of plants tend to compete and so multiple introductions can be detrimental."

One of the studies researchers analyzed focused on three agents (two species of weevils and a fly) that have been released in western North America to control two species of , diffuse and spotted knapweed. The weevils consume the fly larvae, nullifying the effectiveness of the fly.

Explore further: No returning to Eden: Researchers explore how to restore species in a changing world

More information: rspb.royalsocietypublishing.or… /1760/20122756.short

add to favorites email to friend print save as pdf

Related Stories

Rust fungus to tear backbone out of boneseed

Jan 29, 2008

CSIRO’s newly refurbished containment facility for exotic insects and plant pathogens in Canberra is hosting a species of rust fungus which shows promise as a biocontrol agent for the highly invasive plant ...

Predicting the perfect predator

Feb 13, 2008

Garlic mustard has become an invasive species in temperate forests across the United States, choking out native plants on forest floors and threatening ecosystem diversity. University of Illinois ecologist Adam Davis has ...

Overseas lab seeks US weed control 'recruits'

Nov 24, 2010

The search is on for insects, mites, microbes or nematodes that could be used in a biologically based approach to controlling silverleaf nightshade, an invasive weed from the Americas that has spread to southern Europe, Africa, ...

Recommended for you

Study indicates large raptors in Africa used for bushmeat

13 hours ago

Bushmeat, the use of native animal species for food or commercial food sale, has been heavily documented to be a significant factor in the decline of many species of primates and other mammals. However, a new study indicates ...

Noise pollution impacts fish species differently

15 hours ago

Acoustic disturbance has different effects on different species of fish, according to a new study from the Universities of Bristol and Exeter which tested fish anti-predator behaviour.

Insecticides similar to nicotine widespread in Midwest

16 hours ago

Insecticides similar to nicotine, known as neonicotinoids, were found commonly in streams throughout the Midwest, according to a new USGS study. This is the first broad-scale investigation of neonicotinoid ...

User comments : 0