Ecology

Well-known organic insecticide not used enough

Bacillus thuringiensis (Bt for short) was discovered in 1911 and has been used since the 1930s. Today, Bt is the most widely used organic insecticide in the world, but sales still only account for less than 2% of the pesticide market, which is evaluated at $30 billion. “Currently, there are tens of thousands of strains of Bt preserved in storage banks awaiting characterization or typing,” says Jean-Louis Schwartz, a professor in the Department of Physiology at the Université de Montréal.

Schwartz believes that Bt’s day is here, and that can only be a good thing. Last September, the World Health Organization (WHO) launched an appeal to promote the spraying of DDT (dichloro-diphenyl-trichlorethane) in the struggle to eradicate malaria in Africa. Schwartz deplores that approach, pointing out that DDT, a neurotoxic insecticide, has extremely harmful effects. “DDT builds up in the food chain and remains in the environment,” he notes.
Learning more about Bt is important in strategic terms, since this biodegradable insecticide could prove to be extremely valuable over the next few years. “Insects that sting can be the vectors of extremely serious illnesses. Immense quantities of this insecticide are used in countries where malaria and other parasite-borne (onchocerciasis or river blindness) or viral (dengue fever) diseases are raging epidemics.”

For about 15 years, the director of the Biocontrol Network has focused on the molecular and cellular mechanisms of the proteins that form pores in cell membranes, specifically the bacterial proteins produced by Bt, Bacillus sphaericus and E. coli. His work (with Raynald Laprade, Vincent Vachon and many other colleagues in Canada and other countries) is playing a pioneering role in understanding how Bt works, making it more effective as a bio-insecticide and in the struggle to overcome resistance in target organisms. The lab’s most recent work focuses on the clinical utility of natural or genetically modified Bt strains in the fight against cancer. 

Without wanting to sound overly alarmist, Schwartz mentions that global warming is likely to open new territories to subtropical insects that carry infections. “We are seeing these diseases appear in regions like South Carolina and the Mississippi valley. Even the West Nile virus appeared in our latitudes, which no one would have thought possible five years before it happened.”

In medical research, recent experiments by teams from Japan, Korea and Canada have shown that certain strains of Bt produce parasporins, proteins that destroy certain mammalian cancer cells (liver, colon and blood). Subsequent work may lead to clinical applications. “These discoveries have revived interest in Bt,” says Schwartz.