Microbial Biopesticides: Bacteria
Biopesticides based on bacteria have been used to control plant diseases, nematodes, insects, and weeds. Bacteria are present in all soils and are the most abundant micro-organisms in soil samples. Many spore forming and non-spore forming bacteria are known to be effective against a wide spectrum of insects and diseases.
The most well-known and widely used of all biopesticides are insecticides based on Bacillus thuringiensis, commonly referred to as “Bt.” During spore formation, Bt produces insecticidal proteins (know as delta-endotoxins) that kill caterpillar pests , fly and mosquito larvae , or beetles (depending on the subspecies and strain of Bt) that ingest them through feeding in Bt-treated areas. The highly specific delta-endotoxins bind to and destroy the cellular lining of the insect digestive tract, causing the insect to stop feeding and die. Bt has been in continuous commercial use for over 50 years, a record not exceeded by any other insecticide active ingredient. Bacillus sphaericus is another insecticidal bacterium that has been used successfully to control certain mosquito species.
Other bacteria are used for the control of plant pathogens. Certain strains of Bacillus subtilis, Bacillus pumilus, Pseudomonas spp., and Streptomyces spp. increase yield and prevent plant diseases by outcompeting plant pathogens in the rhizosphere, producing anti-fungal compounds, and by promoting plant and root growth.