Most notably, Bt toxins are insecticidal to the larvae of moths and butterflies, beetles, cotton bollworms and flies but are harmless to other forms of life.
This eliminates the need to use large amounts of broad-spectrum insecticides to kill lepidopteran pests (some of which have developed pyrethroid resistance).
A 2006 study done by Cornell researchers, the Center for Chinese Agricultural Policy and the Chinese Academy of Science on Bt cotton farming in China found that after seven years these secondary pests that were normally controlled by pesticide had increased, necessitating the use of pesticides at similar levels to non-Bt cotton and causing less profit for farmers because of the extra expense of GM seeds.
The Cry toxin molecules attach themselves to specific locations on the cadherin-like proteins present on the epithelial cells of the midgut and ion channels are formed which allow the flow of potassium.
[9] Similarly in India and the US, Bt cotton initially alleviated the issues with pests whilst increasing yields and delivering higher profits for farmers.
[10][11][12] Studies showed that the lower levels of pesticide being sprayed on the cotton crops promoted biodiversity by allowing non-target species like ladybirds, lacewings and spiders to become more abundant.
[9] Likewise it was found that integrated pest management strategies (IPM) were becoming more effective due to the lower levels of pesticide encouraging the growth of natural enemy populations.
[9] In India alone widespread adoption of Bt cotton led to 2.4-9 million less cases of pesticide poisoning, with similar reduction also seen in other countries.
[13] After the introduction of Bt cotton in northern China, non-target pests such as mirid bugs (Heteroptera: Miridae) became more abundant, because less pesticides were sprayed.
[15] Main drivers for the widespread resistance in India and China included the high proportion of Bt cotton being planted, 90% and 95% respectively in 2011,[9][16] and few refuge areas.
[18] In 2009, a novel solution to the resistance problem was trialed in Arizona, when sterile male pink bollworms (Pectinophora gossypiella) were released into populations of their wild Bt-resistant counterparts.
[26] Socio-economic surveys confirm that Bt cotton continues to deliver significant and multiple agronomic, economic, environmental and welfare benefits to Indian farmers and society including halved insecticide requirements and a doubling of yields.
The Kenyan government is promoting its use, expecting greatly increased output and some greater filling of its own domestic demand.