Do GMOs reduce pesticide use?

pesticideapplicationThat was one big promise of genetic engineering: fewer chemicals dumped into our soils. But has it worked out? A new report by the nonprofit Organic Center of Boulder says not by a long shot.

The most striking finding is that GE [genetically engineered] crops have been responsible for an increase of 383 million pounds of herbicide use in the U.S. over the first 13 years of commercial use of GE crops.

In the earliest years of GMOs, pesticide use did go down. (Pesticides means all chemicals used to control insects, weeds, and fungi.)

But then something happened. Plants wised up—specifically, the plants farmers didn’t want in their fields, otherwise known as weeds. Weedy plants developed resistance to herbicides.

We might have guessed it would happen. With the rise of antibiotic-resistant bacteria, we watched evolution take place among bacteria. With herbicide-resistant weeds, we are watching plants adapt to their environments—and emerge stronger than before.

The herbicide to which plants have developed resistance is glyphosate, known more famously as Roundup. Today glyphosate-resistant (GR) weeds are threatening whole swaths of cotton, soybeans, and corn throughout the Midwest and South.

GR [glyphosate-resistant] weeds were practically unknown before the introduction of RR [Roundup-Ready] crops in 1996. Today, nine or more GR weeds collectively infest millions of acres of U.S. cropland.

The principal strategy farmers are using in the face of this new threat is—guess what—more herbicide. Which is why herbicide use is rising:


But in some places the weeds are so invasive that farmers have resorted to hoeing them by hand. Here is a photo of workers tackling Palmer amaranth in a GMO-planted cotton field:

weeding cotton

Photo by Brad Luttrell (www.

If there is a bright spot in this report, it is that more farmers are looking for “conventional,” non-GMO, seeds to plant in the face of this alarming development. But not a lot of farmers. The number of acres planted to herbicide-tolerant soybeans dropped by only 1 percent last year and is expected to drop only a couple of percentage points in 2010. One problem is that the supply of conventional seeds has shrunk so drastically that for the coming few years farmers will have no choice but to plant genetically engineered ones.

And one or two percentage points is indeed very small, given that 90 percent of the soybeans and most of the cotton grown in this country are herbicide-tolerant crops, as the following graph from the report shows.

GMO crops

What can you do?

  • Buy organic! The organic label means no GMOs allowed. The most direct way to register your vote for healthy soil, healthy animals, and healthy people is to buy organic foods.
  • Educate yourself on GMO-related issues. The Organic & Non-GMO Report website is a good place to start.
  • Read food labels. If 90 percent of soybeans are herbicide resistant, that means your “healthy” soy-based foods, such as tofu and soymilk, are now almost all GMO based. But all kinds of other foods also contain GMO-based soy, especially in the form of soy lecithin, an emulsifier. Soy lecithin appears in, for example, my favorite Celestial Seasonings herb teas.
  • Become a soil advocate. GMO (herbicide-resistant) crops are changing soil biology, according to a microbiologist with the USDA. I will be happy to post a guest blog from anyone (especially a student) who writes a decent report on GMOs, pesticides, and soil health.

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