What are the advantages and disadvantages of B.T. Cotton?

Answer 1

AdvantagesThere are several advantages in expressing Bt toxins in transgenic Bt crops:

• The level of toxin expression can be very high thus delivering sufficient dosage to the pest.
• The toxin expression is contained within the plant system and hence only those insects that feed on the crop perish.
• The toxin expression can be modulated by using tissue-specific promoters, and replaces the use of synthetic pesticides in the environment. The latter observation has been well documented world-wide.

Possible problemsThe most celebrated problem ever associated with Bt crops was the claim that pollen from Bt maize could kill the monarch butterfly.[22] This report was puzzling because the pollen from most maize hybrids contains much lower levels of Bt than the rest of the plant[23] and led to multiple follow-up studies. In the end, it appears that the initial study was flawed; based on the way the pollen was collected, they collected and fed non-toxic pollen that was mixed with anther walls that did contain Bt toxin.[24] The weight of the evidence is that Bt crops do not pose a risk to the monarch butterfly.[25]

There was also a report in Nature, that Bt maize was contaminating maize in its center of origin.[26] Naturelater "concluded that the evidence available is not sufficient to justify the publication of the original paper."[27] A subsequent large-scale study failed to find any evidence of contamination in Oaxaca.[28]

There is also a hypothetical risk that for example, transgenic maize will crossbreed with wild grass variants, and that the Bt-gene will end up in a natural environment, retaining its toxicity. An event like this would have ecological implications, as well as increasing the risk of Bt resistance arising in the general herbivore population. However, there is no evidence of crossbreeding between maize and wild grasses.

As of 2007, a new phenomenon called Colony Collapse Disorder (CCD) is affecting bee hives all over North America. Initial speculation on possible causes ranged from cell phone and pesticide use[29] to the use of Bt resistant transgenic crops.[30] The Mid-Atlantic Apiculture Research and Extension Consortium published a report on 2007-03-27 that found no evidence that pollen from Bt crops is adversely affecting bees. CCD has since been attributed to a new virus, unrelated to Bt crops.[31]