One of a farmer's worst nightmares is to wake up one day and find his Bt corn field being ravaged by marauding corn borers that somehow developed resistance to the pesticide gene the corn variety carries.

That the corn borers could withstand Bt corn is not far-fetched because all living organisms continually adapt through the natural selection stresses in the environment.

A corn borer could be resistant to the toxin produced by Bacillus thuringiensis in Bt corn varieties if the insect does not convert the Bt protein into a toxic form and allow it to bind to its gut and form crystals and rupture cell walls.

No 'super pests'

But the concept to developing a "super pest," one that cannot be controlled or overcome, contradicts the principles of biology, according to the United States Institute of Food Technologists.

The institute said the ability of a pest population to adapt to pesticides or genes used to control it is nature's way of assuring its survival. But even if the pests develop resistance to one pesticide gene, they will still be vulnerable to new or older control mechanisms such as a different pesticide or a remodified plant.

With an increase planting area for Bt corn, there will also be more corn borer with one or two copies of resistance genes that could survive and produce more offspring.

Keeping records

But keeping good records and implementing a comprehensive insect resistance management (IRM) strategy will help delay this resistance development.

In genetically modified plant like Bt corn, scientists can rotate pest-resistance genes in a plant, modify the plant's resistance mechanisms or transfer more than one pest resistant gene to the plant.

Genetic mixing 

The movement of corn borer adults between Bt and non-Bt fields is important for genetic mixing of resistant and susceptible types. Thus, planting some unmodified corn crops in or adjacent to a field of Bt corn crops will keep the vulnerability traits in the gene pool of pests.

Crop rotation is also effective in minimizing increases in pest population.

An example of an IRM was developed in 1997 by the Canadian Corn Pest Coalition against corn borer.

It used a high Bt dosage in Bt corn varieties while providing refuge to non-Bt corn hybrids that do not contain Bt proteins within close proximity of the Bt crops.