For the last 100 years, beekeepers have experienced colony losses from bacteria, (foulbrood), mites (varroa and tracheal) and other pathogens. These problems are dealt with by using antibiotics, miticides and and other methods of pest management. Losses are slow and expected and beekeepers know how to limit the destruction. This new mass die-off is different in that it is virtually instantaneous with no warning of the impending collapse.
John McDonald, a bee keeper in Pennsyvania with a background in biology, speculated that genetically modified crops could play a role in CCD. Although the government constantly reassures us that these genetic manipulations are safe for both humans and the environment, his hope is that looking more closely at these issues might raise questions about those assumptions.
The common bacterium, bacillus thuringiensis (Bt) supplies the most commonly used segment of transgenic DNA. Bt has been used for decades by farmers and gardeners to control crop damage from butterfy larvae. Now, instead of spraying this bacterium directly on the crops, where it is eaten only by the target insects, the genes containing the insecticidal traits are incorporated into the genome of the plant itself. As the genetically modified plant grows, these Bt genes are replicated in every cell of the plant, including pollen. Therefore, every cell of each GM plant contains its own poison aimed to kill the target insect. The target insects consume some portion of the plant, then once ingested, the toxin produced by the Bt genes causes crystallization in the guts of boring larvae and thus death. The primary toxin is a protein called Cry1Ab. In the case of field corn, the targeted insects are stem and root-borers and butterfly larvae.
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Another study indicating that Bt may be contributing to the death of honey bees was undertaken in Mexico. This study compared the effects on young adult honeybees of 2 concentrations of Cry1AB (3 and 5000 parts per billion) to a chemical pesticide, imidacloprid. 3 different effects were evaluated by the researchers:
1. Survival of honeybees during sub-chronic exposure to Cry1Ab.
2. Feeding behavior.
3. Learning performance at the time that honeybees become foragers.
Neither test concentration of Cry1Ab had lethal effects on the honeybees, however, when exposed to the higher concentration, feeding behavior was affected. The bees spent longer ingesting the syrup which contained the Cry1Ab which could mean smaller amounts of pollen would be collected. These bees also had impaired learning performance. Honeybees normally do not continue responding to an odor when no food is present, but should be discouraged and seek other sources. These bees continued responding to the odor which again, could affect pollen gathering efficiency. This study indicates that although Bt is not directly lethal to honeybees, it could indirectly lead to colony death due to failure to collect enough food to sustain the hive.
http://waronyou.com/topics/genetically-modified-crops-implicated-in-honeybee-colony-collapse-disorder/
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