GM Cotton in China Drives Off One Pest, But Another Sneaks In

By Andrew Moseman | May 14, 2010 2:46 pm

MiridOne pest withers; another takes its place.

The Chinese government in 1997 approved Bt cotton. The crop, produced by U.S. agribusiness giant Monsanto, is genetically modified to produce a toxin that kills the bollworm, which has wreaked havoc on cotton crops. For its intended use, Bt cotton worked great: As DISCOVER covered in 2008, bollworms were in steep decline not only in cotton fields, but also in neighboring fields of corn and soybeans. But nature, as they say, abhors a vacuum,  and targeting just one pest opens the door for others to come in. According to a decade-long study published in Science this week, it’s happening.

The new pest plaguing the 4 million hectares of Bt cotton in China is the mirid bug, research leader Kongming Wu says.

Numbers of mirid bugs (insects of the Miridae family), previously only minor pests in northern China, have increased 12-fold since 1997, they found. “Mirids are now a main pest in the region,” says Wu. “Their rise in abundance is associated with the scale of Bt cotton cultivation” [Nature].

Operating in northern China, Wu’s team monitored how much insecticide farmers used from the early 1990s up through 2008. They also tracked the mirid population from the time Bt cotton was introduced up to 2008.

Before switching to GM cotton, farmers used more broad-spectrum insecticides to kill bollworms and other pests. But as more farmers began growing Bt cotton, their use of sprays declined, leading to a steady rise in pests, including mirid bugs [The Guardian].

Farmers have always been playing cat-and-mouse with pests and weeds, of course. The reports last week of weeds becoming increasingly resistant to the weed-killer Roundup was another reminder that nature adapts to our tricks, so while GM crops are often great at the their initial purpose, circumstances change. Cotton itself has been through many cycles of this before.

For example, the boll weevil was once the main worldwide threat to cotton. As farmers sprayed pesticides against the weevils, bollworms developed resistance and rose to become the primary pest. Similarly, stink bugs have replaced bollworms as the primary pest in southeastern United States since Bt cotton was introduced [Nature].

Related Content:
80beats: Genetically Modified Cotton Plants Protect Their Neighbors from Pests
80beats: Evolution in Action: Roundup-Ready Crops Create Roundup-Resistant Superweeds
80beats: Biotech Potato Wins European Approval; May Signal a Larger Shift on GM Crops
80beats: India Says No to Genetically Modified Eggplants

Image: flickr / J. Coelho

  • Jay Fox

    This is exactly why these GM crops are a questionable strategy, with possibly dangerous consequences. A target insect, in this case, actually declines but is replaced by something even worse. So what, now, they going to develop another “poisonous plug-in” for the cotton genome? Are we supposed to believe them when they say it’s safe? At what point does the altered plant become hazardous for us to use? How would we know?

    The article didn’t say it, but there probably will be an increase in pesticide use as these new bugs continue to take over for their exterminated predecessors. So farmers will be where they were before, except that now they will have to purchase their seeds every year from Monsanto. This is progress? This is how GM crops help us?

    The claim is that these genetic modifications only affect certain parts of the plant that insects target. Supposedly the parts that we use are somehow left unaffected. I see two problems with this.

    First, what’s to prevent opportunistic insects from targeting the parts of the plant we want to use? Are we going to make that part poisonous? Would we then be willing to eat trace amounts of insecticide with every bite of that food? You can replace the word insecticide with herbicide and continue this argument anew concerning Roundup Ready crops.

    Second, how do we really know what parts of the plant are affected? To date, most of the “scientific” studies relating to GM crops are very tightly controlled by Monsanto. Not too much independent stuff out there. If Monsanto was serious about their claims of safety, they’d be more forthcoming. By not being so, they foster suspicion.

    Just because we can do something, doesn’t mean we should. As the bug situation shows (and the weed problems, too), we cannot predict the outcome of these massive experiments on the planet. Sooner or later, something worse than Star-Link corn is going to happen.

  • JJdoubleJ

    What we dont know JAY is where we would be without GM crops, other than we would’ve sprayed millions of more gallons of pesticides already, with dramatic declines in yield.

  • Geraldine

    Pesticides and herbicides do not make declines in production. Studies done from around the world have shown that GM crops rarely do better, and in some cases, especially drought stricken areas, they do worse.
    Pesticides and herbicides are still used on crops, and in some areas that have planted GM crops, they have to be used extensively because other pests and predators will fill that vacuum.
    The May issue in Discover about the cassava root is a prime example of what can be accomplished without resorting to GM foods. And…no one is going to charge the farmers an exhorbitant amount of money to use the improved cassava root.

  • Mark

    I see that alot of people are questioning the simple reasons why we choose to use GM crops, I see opposition against using it based on someone’s opinions, what i don’t see is someone offering solutions. There is a word for that, it’s called complaining.

    Unless you can find a solution to this problem, i believe that we should leave the question of whether or not we should use GM crops to people who have degree’s in this field. I do not have a Degree in any Bio-science, therefore I can’t offer solutions to the problem. Please feel free to offer a solution if you have a valid one, otherwise just leave it to the experts in the field and just be quite.

  • Bernd

    As a consumer I shouldn’t have to provide solutions. I want my environment healty and not be killed by some super weed oder super bug. I also want my choice to eat GM food or not to eat GM food so provide a label or forget it.

    If you can’ t tolerate losses in some years you shouldn’t grow crops. There isn’t a 100% solution to get huge results EVERY YEAR. That’s what governments or “farm unions” are for to help you in weak years.


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