bio insecticides

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Bioinsecticides


Bioinsectide Crystals used to kill insect larvae

Safer Pest Control
Today's Commercial farming relies on widespread pesticide use to produce a large volume of food. The rub is that most exisitng chemical pesticides don't degrade when introduced to the environment and can be toxic. Yet insects still cause billions of dollars of damage each year to agriculture, forests and other vegetation. That's because they've been genetically programmed by nature for survival.

"Insects, like bateria, have been able to survive for long periods of time by continuous genectic adaptation. Close to 400 species of insects have developed different degrees of resistance to chemical pesticides over the past 50 years," says Argyrios Margaritis, PhD, P.Eng., a professor of biochemical engineering at the University of Western Ontario. He says that if we stick to traditional ways of combating this problem, we'll have only two choices: increase the concentration of pesticides sprayed on vegetation, or develop new chemicals the bugs haven't been exposed to yet. But both options are "viscious circles," he says. If the choice is to increase the concentration of pesticides used, insects will develop even greater resistance with results that could be "environmentally disastrous." New chemicals, for their part, are costly to develop and experience shows that insects will eventually tend to become resistant to them too.

But Margaritis is betting bugs will find his "bioinsecticide" too lethal to survive. To produce his deadly brew, Margaritis grows Bacillus thuringiensis, a natural soil microorganism, in a bioreactor developed by his team at Western. With the addition of nutrients and oxygen, the microorganism matures and eventually produces delta endotoxin, a crystal protein that is extracted and then suspended in solution. When applied to vegetation, it quickly kills insect larvae that eat it. Other bateria that live in the soil consume any of the solution that remains, as a life-giving nutrient. Not only is the bioinsecticide non-toxic, results so far indicate that the degree and rate of mutation of insect species exposed to it is much lower than if they were to chemical insecticides, Margaritis says.

A further advantage is that the large variety of avaliable crystal proteins are selective, killing only certain species of insect larvae feeding on particular species of plants. The trouble with some chemicals, says Margaritis, is that while they kill the bad guys they can also eliminate all the other living species that are part of a balanced ecosystem. He says the large number of proteins is also a factor in minimizing the chances of frequency of insect mutations.

In the works, he says, are larger scale trials to provide a more realistic picture of the bioinsecticide's cost. "Eventually," says Margaritis, "we hope to find an industrial partner to further scale-up our process. But our preliminary cost estimate looks very promising."

Source : Professional Engineers Ontario - Engineering Dimensions May/June 2001, page 29.