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Aphids Attack GM Cotton

Posted May 13 2013 1:14pm
Aphids Attack GM Cotton Many ecologists and scientists have long warned about the potential of secondary pests emerging from the mass cultivation of crops genetically engineered with Cry proteins derived from Bacillus thuringiensis (Bt) in order to kill target pests. Bt cotton farmers have for some time now reported the emergence of secondary pests, such as aphids. This has been attributed to reduced pesticide use by various quarters. A recent study has shed new light on this problem by establishing a link between the rise in aphids in Bt cotton and a weakened plant defense system. The study, published in the journal Proceedings of the Royal Society B in March 2013, found that Bt cotton plants had lower levels of defense compounds known as terpenoids that are normally released in response to caterpillar attacks. However, as Bt cotton plants kill the caterpillars, the lowered terpenoid levels make the plants an easy target for aphids which are Bt-insensitive. The researchers studied the correlation between Bt and non-Bt cotton plants, defense compound levels and aphid populations under both glasshouse and field conditions. They found a positive correlation between reduced terpenoid levels and aphid populations under the former and a lesser link under the latter.The implications of this study are particularly important─ the findings have provided evidence of non-target herbivores developing into (secondary) pests when primary pests are addressed in isolation, such as in Bt cotton crops. This phenomenon is similar to that which first arose (and continues to arise) with the persistent use of chemical pesticides and industrial agricultural systems that fail to take into account ecological balance. The full report can be downloaded here: Aphids can not become immune to or or
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