Pest-Resistant Genetically Modified Corn, Combined with the Environmental Protection Agency’s Regulatory Attempt to Keep it Effective, Has Worked

© 2010 Peter Free

 

10 November 2010

 

Beneath the hubbub of “don’t mess with it” outrage, some regulated advances in biotechnology appear to work as advertised

 

American farmers quickly adopted pest-resistant genetically modified corn when it became available in 1996.  The modification inserted proteins from the bacterium Bacillus thuringensis (Bt) into the corn genome.

 

This modification was desirable from the farmers’ perspective because some agricultural pests die when they eat Bt proteins.  Among susceptible moochers is the European corn borer, Ostrinia nubilalis.  Before Bt-treated corn, Ostrinia caused $1 billion worth of annual damage in the United States.

 

Over the fourteen years since the first genetically modified corn planting, farmers in Illinois, Iowa, Minnesota, Nebraska, and Wisconsin have prevented almost $6.9 billion in damage.

 

Citations

 

W. D. Hutchinson et al., Areawide Suppression of European Corn Borer with Bt Maize Reaps Savings to Non-Bt Maize Growers, Science 330(6001): 222-225 (08 October 2010)

 

Bruce E. Tabashnik, Communal Benefits of Transgenic Corn, Science 330(6001): 189-190 (08 October 2010)

 

But is was more complicated than simply planting modified corn

 

Simply modifying the corn was not enough.  Ordinarily, quickly-reproducing organisms rapidly evolve metabolic resistance to protect themselves against susceptibility to environmental hazards.

 

Consequently, the Environmental Protection Agency implemented regulations that required farmers to plant unmodified corn alongside the modified variety.  The unmodified corn patches are called “refuges.”

 

The EPA reasoned that corn borer females cannot distinguish between modified and unmodified corn.  Consequently, they lay eggs on both kinds.  Though the larvae feeding on modified corn will die, those on unmodified corn will not.  That is actually the goal.

 

Some corn borers eating genetically modified corn will evolve resistance genes that protect them against the Bt poison.  They pass a set of these genes to their offspring.  If these offspring mate with an equally resistant partner, their kids will also be resistant because both copies of their genome will carry the protective trait.

 

However, if the resistance gene is not effective in conferring protection against BT by itself ─ meaning, in grossly oversimplified terms, that it is not a dominant gene ─ offspring that have only one resistant parent will die when they feed on modified corn.  Their one resistance gene is not enough to protect them against the Bt poison.

 

The EPA knew that, if there were no safe food sources for corn borers, the whole population would be exposed to the killing corn and Ostrinia would soon evolve resistance to Bt.  (Why this is so involves a complicated combination of molecular biology and statistics.)

 

On the other hand, if a sizeable portion of the corn borer population remained vulnerable, and insect mothers could not distinguish between modified corn and safe corn, the corn borer genome would be much slower to evolve protection against Bt.

 

With these facts in mind, the EPA concluded that it could temporally extend the effectiveness of Bt-modified corn by requiring significant the planting of adjacent plots of unmodified corn.  Twenty to fifty percent of on-farm corn acreage had to be of the non-modified type, and those plots had to be within 0.8 kilometers of the modified corn.

 

So who saved the most money?

 

Of the $6.9 billion saved over 14 years by reducing crop losses, 67 percent of the savings went to non-Bt growers.  Genetically modified corn growers had the added expense of the buying Bt corn each year.

 

In the longer run

 

Given the usually adaptable nature of things biological, the corn borers are eventually going to win.  Until we toss them another curve.

 

Moral? ─ thinking helps

 

There is risk in everything.  Even in sitting still.

 

Better to move forward with brain, than stagnate without.