In 2001, Bt176 varieties were voluntarily withdrawn from the list of approved varieties by the Environmental Protection Agency when it was found to have little or no Bt expression in the ears and was not found to be effective against second generation corn borers. (Current status of Bt Corn Hybrids, 2005)
Upon sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal δ-endotoxins (Cry toxins) which are encoded by cry genes. Cry toxins have specific activities against species of the orders Lepidoptera (Moths and Butterflies), Diptera (Flies and Mosquitoes) and Coleoptera (Beetles). Thus, B. thuringiensis serves as an important reservoir of Cry toxins and cry genes for production of biological insecticides and insect-resistant genetically modified crops. ... Spores and crystalline insecticidal proteins produced by B. thuringiensis are used as specific insecticides under trade names such as Dipel and Thuricide. Because of their specificity, these pesticides are regarded as environmentally friendly, with little or no effect on humans, wildlife, pollinators, and most other beneficial insects. The Belgian company Plant Genetic Systems was the first company (in 1985) to develop genetically engineered (tobacco) plants with insect tolerance by expressing cry genes from B. thuringiensis.
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Spores and crystalline insecticidal proteins produced by B. thuringiensis are used as specific insecticides under trade names such as Dipel and Thuricide. Because of their specificity, these pesticides are regarded as environmentally friendly, with little or no effect on humans, wildlife, pollinators, and most other beneficial insects. The Belgian company Plant Genetic Systems was the first company (in 1985) to develop genetically engineered (tobacco) plants with insect tolerance by expressing cry genes from B. thuringiensis.
The researcher (working on corn borer resistance) said different strains of bacillus thurengiensis produced species-specific toxins. I wonder how true that will turn out to be (meaning, in time, will we not learn there's some bleed-over to other species than the target?) - though I still doubt the (more than marginal) effect on bees of BT corn, since bees don't collect that pollen.
Bacillus thuringiensis
For many years, Bt was available only for control of lepidoptera, using a highly potent strain (B. thuringiensis var kurstaki). This strain still forms the basis of many Bt formulations. Further screening of a large number of other Bt strains revealed some that are active against larvae of coleoptera (beetles) or diptera (small flies, mosquitoes). Most of these strains have the same basic toxin structure, but differ in insect host range, perhaps because of different degrees of binding affinity to the toxin receptors in the insect gut. For example, the toxins produced by B. thuringiensis var aizawai have somewhat different toxins from those of B.t. var kurstaki and they are highly specific to lepidoptera, with no effect on other insects. The many commercial strains for control of lepidoptera are marketed under various trade names such as Biobit®, Dipel®, Javelin®, etc. In contrast, the toxins produced by strains of B.t. var israelensis are highly active against simuliid blackfly vectors of some tropical diseases, and also against fungus gnat larvae and some types of mosquito (especially Aedes species, but higher toxin doses are needed for control of Culex spp. and Anopheles spp.). Trade names for these products include Skeetal®, Vectobac® and Mosquito Attack®. Strains of B.t. var san diego or B.t. var tenebrionis are marketed for control of some coleoptera - especially for control of the important Colorado potato beetle.
For many years, Bt was available only for control of lepidoptera, using a highly potent strain (B. thuringiensis var kurstaki). This strain still forms the basis of many Bt formulations. Further screening of a large number of other Bt strains revealed some that are active against larvae of coleoptera (beetles) or diptera (small flies, mosquitoes). Most of these strains have the same basic toxin structure, but differ in insect host range, perhaps because of different degrees of binding affinity to the toxin receptors in the insect gut. For example, the toxins produced by B. thuringiensis var aizawai have somewhat different toxins from those of B.t. var kurstaki and they are highly specific to lepidoptera, with no effect on other insects. The many commercial strains for control of lepidoptera are marketed under various trade names such as Biobit®, Dipel®, Javelin®, etc.
In contrast, the toxins produced by strains of B.t. var israelensis are highly active against simuliid blackfly vectors of some tropical diseases, and also against fungus gnat larvae and some types of mosquito (especially Aedes species, but higher toxin doses are needed for control of Culex spp. and Anopheles spp.). Trade names for these products include Skeetal®, Vectobac® and Mosquito Attack®.
Strains of B.t. var san diego or B.t. var tenebrionis are marketed for control of some coleoptera - especially for control of the important Colorado potato beetle.
Bees are hymenoptera.
