To determine whether there was an effect, though, would require analysis of the larvae in the hive, since Bt kills larvae (a crystal protein perforates their intestine). A dead colony would then be one whose larvae had all died, and therefore whose adult insects were not replaced.
However, bees have been suffering for years now from a combination of attacks on their robustness and resistance. Chemical pesticides (fipronil and imidaclopride in particular) have been associated with colony deaths (and their use has been restricted). A parasite, the varroa mite, has settled in with a vengeance. (I've also been hearing about new killer hornets that attack hives...) It's possible that BT crops will add to this weakening by putting another bee-negative substance out there.
As to whether the disappearance of bees would be catastrophic, so many plants are pollinated by them the ecological consequences would be enormous. Human foods at risk, apart from rapeseed and sunflower (oils) would include most kinds of fruit. When locusts move on, they leave nothing behind
Bt Corn is used in Spain (about 12% of all corn) but not on any significant scale in other European countries. Studies have not shown any dramatic impact on the environment, but the jury is still out on this (ECOLOGICAL IMPACTS OF GENETICALLY ENGINEERED CROPS: TEN YEARS OF FIELD RESEARCH AND COMMERCIAL CULTIVATION Olivier Sanvido, Michèle Stark, Jörg Romeis and Franz Bigler December, 2006) I can recommend this study (you can find it at http://www.isb.vt.edu/articles/dec0603.htm) because I know the scientists and they are serious researchers not working for Monsanto or Greenpeace.
In 2001, Bt176 varieties were voluntarily withdrawn from the list of approved varieties by the Environmental Protection Agency when it was found to have little or no Bt expression in the ears and was not found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.
...
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. When locusts move on, they leave nothing behind
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. When locusts move on, they leave nothing behind
The striking feature of CCD is that bees die in fields, outside beehives. Adults bees are affected, right at work. Larvae might suffer as well - but by definition, CCD is not a failure of the reproductive chain.
