Beneficial insects, nematodes not harmed by genetically modified, insect-resistant crops

Feb 02, 2014
This shows Geocoris punctipes feeding on an unidentified Homopteran. Credit: Russ Ottens, University of Georgia, Bugwood.org

A large body of literature has shown that genetically-modified plants that produce proteins from the bacterium Bacillus thuringiensis (Bt) to protect themselves from insect pests have little to no effect on a wide range of nontarget insects. However, concerns about Bt crops still exist. Now two new studies using more exacting methods show that Bt crops have no negative effects on two beneficial insect predators or on a beneficial, entomopathogenic nematode.

In an article in the February 2014 issue of Environmental Entomology, called "Using Resistant Prey Demonstrates that Bt Plants Producing Cry1Ac, Cry2Ab, and Cry1F Have No Negative Effects on Geocoris punctipes and Orius insidiosus," researchers used caterpillars that were known to be resistant to Bt proteins and fed them Bt maize and Bt cotton. They then fed the caterpillars to two common, beneficial, predatory insects—insidious flower bugs (Orius insidiosus), and big-eyed bugs (Geocoris punctipes)—for two generations and compared them to another group of predators that consumed caterpillars fed on non-Bt plants.

The researchers found that the survival, development, adult mass, fecundity, and fertility of the insect predators in both groups were similar, regardless of whether they consumed caterpillars that fed on Bt plants or non-Bt plants.

"This research demonstrates that the current Bt proteins used in corn and cotton crops globally do not harm Geocoris punctipes or Orius insidious, two important insect predators that help suppress pest populations on corn, cotton, and many other crops," said Dr. Anthony Shelton, a professor of entomology at Cornell University and one of the co-authors. "By using caterpillars resistant to the Bt proteins in this study, we were able to remove any 'host quality effects' that might have led to spurious misinterpretation of the results. This work demonstrated that the caterpillars consumed the Bt proteins, and the predators consumed the Bt proteins when they fed on the caterpillars, but they did not suffer any harm even over multiple generations."

This shows Orius insidiosus feeding on an insect egg. Credit: John Ruberson, University of Georgia, Bugwood.org

In a similar article appearing in the February 2014 issue of the Journal of Economic Entomology called "Tri-Trophic Studies Using Cry1Ac-Resistant Plutella xylostella Demonstrate No Adverse Effects of Cry1Ac on the Entomopathogenic Nematode, Heterorhabditis bacteriophora," Shelton and his colleagues used similar methods and found that an important nematode predator was not harmed when it ingested another Bt protein. For this study, resistant caterpillars were fed Bt broccoli and then exposed to Heterorhabditis bacteriophora, a beneficial nematode that preys on insects.

The researchers found that the virulence, reproductive potential, and time of emergence of the nematodes that consumed Bt-fed were not significantly affected, compared to nematodes that did not ingest the Bt protein.

"This is the first report we are aware of in which a nematode predator has been tested in such detail against a Bt ," Dr. Shelton said.

"Together, these two studies add to the scientific literature demonstrating that Bt plants can control targeted insect pests while not harming important natural enemies that help suppress pest species and maintain biodiversity in agricultural systems," Shelton added.

Explore further: Scientists offer recommendations for delaying resistance to Bt corn in western corn rootworm

More information: The Environmental Entomology article is avaliabe at: dx.doi.org/10.1603/EN13184
The Journal of Economic Entomology article is avaliabe at: dx.doi.org/10.1603/EC13310

add to favorites email to friend print save as pdf

Related Stories

New bacteria toxins against resistant insect pests

Oct 19, 2011

Toxins from Bacillus thuringiensis bacteria (Bt toxins) are used in organic and conventional farming to manage pest insects. Sprayed as pesticides or produced in genetically modified plants, Bt toxins, us ...

Bt sweet corn can reduce insecticide use

Oct 07, 2013

Since 1996, corn containing a gene that allows it to create a protein that is toxic to certain insects, yet safe for human consumption, has been grown in the United States. However, most of this "Bt corn" ...

Researchers identify insect resistance to Bt pesticide

Aug 30, 2011

For the first time, researchers have identified how cabbage looper caterpillars in the field develop resistance to the bacterium Bacillus thuringiensis (Bt), which naturally occurs in the soil and on plants ...

Recommended for you

Genetically tracking farmed fish escaping into the wild

16 hours ago

European sea product consumption is on the rise. With overfishing being a threat to the natural balance of the ocean, the alternative is to turn to aquaculture, the industrial production of fish and seafood. ...

France fights back Asian hornet invader

19 hours ago

They slipped into southwest France 10 years ago in a pottery shipment from China and have since invaded more than half the country, which is fighting back with drones, poisoned rods and even chickens.

Tide turns for shark fin in China

20 hours ago

A sprawling market floor in Guangzhou was once a prime location for shark fin, one of China's most expensive delicacies. But now it lies deserted, thanks to a ban from official banquet tables and a celebrity-driven ...

Manatees could lose their endangered species status

Aug 19, 2014

About 2,500 manatees have perished in Florida over the last four years, heightening tension between conservationists and property owners as federal officials prepare to decide whether to down-list the creature to threatened ...

User comments : 0