| Bacillus Thuringiensis
Biting fly control was first motivated
by mining activities and hydro-electrical activities in
northern Quebec . Chemical adulticides and larvicides dominated
control efforts from 1970-1984. Since then, however, the
biological insecticide Bacillus
thuringiensis israelensis ( B.t.i. ) ( B.t. H-14)
has been the most effective, cost saving, and environmentally
friendly control method. Applied to aquatic habitats containing
mosquitoes and black flies larvae, the bacteria is activated
in the larvae's digestive system where a toxic protein
is released, killing the insect.
Ordinarily it is non-toxic but when activated, the bacterium B.t.i. releases
certain proteins which form crystals. The crystals dissolve
in an alkaline medium, characteristically found in the
digestive tract of mosquito and black fly larvae. The crystals
release peptides which bind to and perforate the walls
of the digestive tract, causing death within a few hours
or a few days. The crystals can be harvested in large quantities
and stored for use as larvicide. Application of these crystals
over larval habitats kills them thus preventing pupation
and emergence of adults.
The action of B.t.i. is very selective;
it is only activated when swallowed by mosquitoes or
black flies. Additionally, it does not present any effect
on other fauna or on the environment. The World Health
Organization (WHO) issued a document in February of 2000
entitled, "International
program on chemical safety (IPCS)- Environmental Health
Criteria 217; Bacillus thuringiensis ". It revealed
that B.t.i. used for controlling biting insects
presented no danger to human health or to the environment.
The crystals extracted from this bacterium also degraded
within a few days. Biological control programs therefore
require several treatments in order to attack the successive
larval generations throughout the summer.
B.t.i . ( Bacillus thuringiensis israelensis )
has been widely used in Canada for several years and has
been the subject of many studies. Results showed very high
success rates at very low doses, giving it a competitive
edge. Treatments are preceded by monitoring operations
to optimize product usage. Competent entomological technicians
sample all aquatic habitats deemed suitable for larval
development. These control operations are performed throughout
the season and the data collected are analyzed in order
to coordinate and schedule treatments. Without rigorous
monitoring the high efficacy and proper pesticide application
would not be possible.
The popularity of biological control programs is correlated
with the increasing demands of an informed population in
search of higher standards of living. Biological control
programs support ecologically wise resource management.
Fact
Sheet on the Bacillus thuringiensis
subspecies israelensis (Bti) (.PDF)
Health Canada's Pest Management Regulatory Agency (PMRA), is the federal agency
responsible for the regulation of pest control products in Canada.
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