I am often asked, “Why do you grow Bt corn?”
The answer is pretty easy. It has the least environmental impact to control the pests that I have present in my corn field.
It’s a simple answer to a complex question. Let me tell you why.
First let me address what Bt is. It stands for Bacillus thuringiensis (Bt). It’s a common bacterium that occurs naturally in the soil. Bt produces a protein that paralyzes the larvae of some harmful insects, including the cotton bollworm and the Asian and European corn borers, all of which are common plant pests whose infestations can produce devastating effects on important crops. Bt has been used for decades as an insecticide by farmers worldwide. Organic farming in particular has benefited from the Bt insecticide, as it is one of the very few pesticides permitted by organic standards. It’s applied either as a spray or as ground applications.
Scientists have taken the Bt gene responsible for the production of the natural insecticidal protein from the bacterium and engineered it into the genome of plants. Thus, these plants have a built-in mechanism of protection against targeted pests. The protein produced by the plants does not get washed away, nor is it destroyed by sunlight. The plant is thus protected from the bollworm or the corn borer round the clock regardless of the situation. Farmers who use crops with the Bt built in use far less pesticides than do those who spray Bt. The GM Bt is ideal as it only targets destructive insects and has been shown to be entirely harmless to humans. (Humans and a majority of beneficial insects don’t have the receptors in the gut for it to affect them.
Now back to the farm. As farmers, we tend to group corn pests into two categories–above ground and below ground. Examples of above ground pests are European Corn Borer, Stalk Borer, Fall Armyworm, Earworm, Cutworms and Western Bean Cutworm. Below ground pests are fewer, but equally devastating. The most damaging below ground pest is the Corn Rootworm. There are two main types that effect corn in the upper Midwest, Northern corn rootworm and Western corn rootworm. There are other below ground pests like wireworm and white grubs, but those pests mainly affect young corn plants and that damage is not as widespread as the damage caused by corn rootworms.
You see, life as a corn plant is SCARY! From the time seed is placed in the ground, the attacks come from every angle. For now, I’d like to focus on the above ground pests. I’ll cover the below ground pests in another post.
Prior to 1996, we had two choices - treat the above ground pests with a broad spectrum insecticide as they hit economically damaging thresholds, or allow the damage to occur and sustain a financial loss caused by reduced yields. We could apply insecticides appropriate for the pest either by a sprayer driven between the corn rows, or via aerial application. It was a nasty job. Most insecticides are relatively safe with proper handling precautions, but why expose yourself when you don’t have to. I didn’t like being around the stuff, applying it, or the effects it had on non-target species. Those insecticides we used also killed non-target pests like ladybugs, moths, and butterflies were killed. Beneficial insects like Asian Lady Beetles, Praying Mantis, and Green Lacewings that feed on pests were killed also. It was a double-whammy of death, but largely unavoidable.
The first effective Bt event, Yieldguard I, changed all that for farmers in 1996. We were finally given a tool for our toolbox that controlled economically damaging pests that didn’t also affect the beneficial predators. Let me repeat that. Kill the bad bugs, let the good bugs live. No more handling insecticide. No more killing of off-target species like honeybees, moths, beneficial predators, and butterflies.
As much as I love to run the film clip of the Air Cavalry assault scene in "Apocalypse Now” in my head when I call in the spray planes, it makes much more sense to go in with a Navy Seal-like surgical strike. Take out the bad bugs, without the collateral damage to the good bugs. Would I rather use Napalm or a surgical strike? Would you?
The choice is clear to me. It isn’t a difficult decision to control pests using Bt producing plants instead of broad-spectrum insecticides. It just makes good stewardship sense, and apparently not just to me. In this recently released study conducted by USDA, researchers found: “Farmers generally use less insecticide when they plant Bt corn and Bt cotton. Corn insecticide use by both GE seed adopters and nonadopters has decreased—only 9 percent of all U.S. corn farmers used insecticides in 2010. Insecticide use on corn farms declined from 0.21 pound per planted acre in 1995 to 0.02 pound in 2010. This is consistent with the steady decline in European corn borer populations over the last decade that has been shown to be a direct result of Bt adoption.”
The last statement is a nod to the “Halo Effect” that has been noted since the wide adoption of transgenic crops, discussed in this Genetic Literacy Project article by Jeremy Summers—all farmers, including conventional and organic farmers, get the ‘free’ benefits that come from GM farmers using corn with a built in natural pesticide. It’s a win-win for integrated pest management for non-Bt crops to have Bt crops nearby,
The lower impact on non-target species was confirmed in this South African Study that found Bt crops have a similar diversity of animal and insect life compared to non-Bt fields. I haven’t needed to apply a non-selective insecticide since the advent of Bt corn, and don’t intend to. At any given time throughout the growing season, there is an abundance of invertebrate life in my fields.
Although Yieldguard I was the first to market, it has been superseded by a more effective product, Yieldguard II. Other companies have similar technologies like Herculex and Agrisure CB, to name a few. All have the same idea in mind - take out the bad bugs, do no harm to the good bugs.
Planting Bt corn instead of applying an insecticide to combat an economically damaging pest makes good sense to me, and great sense for the environment.
The good bugs would probably like to thank me also.
Dave Walton, a contributing columnist to the GLP, is a full-time farmer in Cedar County, Iowa growing GM and non-GM corn, soybeans, alfalfa and pasture on about 500 acres of the world’s most productive soil.
- New twist on the China-Viptera GMO corn controversy: Customers are talking—is Syngenta listening? Genetic Literacy Project
- Bt sweet corn yields higher, require less pesticides, cuts biosafety costs, Information Systems for Biotechnology
- Researchers confirm Bt corn’s benefits aside from pest resistance, Crop Biotech Update (ISAAA)