An Overview of Biopesticides and Transgenic Crops

The natural ecosystem maintains a delicate balance between pests and predators. Pest insects can be controlled by the artificial release of predators. One example is a parasitic wasp, Diadegma insulare. The adult female wasp lays eggs in a Plutella xylostella larva and pupates inside the cocoon of the mature larva. This and other insect predators are available commercially, but the usage is limited. Protozoa and nematodes are also used in insect pest control. One example of a protozoan that effectively infects locusts and controls the population is Nosema locustae. A commercially available nematode insect control agent is Steinemema carpocapsae. This nematode parasitizes scarab larvae with a symbiotic Photorhabdus bacterium that produces insecticidal toxins. 

Among these different biopesticides, bacterial biopesticides are the most intensively studied and widely used. Several insect pathogenic bacteria are known to produce proteins toxic to certain insects. Bacillus thurin ensis (Bt) is the most well-known bacterium for its potent insecticidal proteins. These proteins are highly specific to certain orders of insects. Insects sensitive to Bt include those of Coleoptera, Diptera, and Lepidoptera. Bacillus sphaericus and Clostridium bifermentans are known for their mosquitocidal proteins. Paenibadllus popilliae produces a scarab active toxin structurally similar to common insecticidal proteins 

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