The agricultural gains by Bt cotton farmers seems to be at the cost of other farmers. The bollworm, which the Bt cotton is resistant to, has now found new hosts in other varieties of plants, putting them at risk. [...] the insect, which belongs to the butterfly family, has migrated to non-Bt plants such as tomato, pigeon pea, chickpea, sorghum and maize. [...] field observations show that the shifting of bollworm from Bt cotton to food crops has resulted in farmers losing at least 20 per cent of their yield. Thanks to the pest migration, the bollworm has found a continuous life, from one season to another, said M.A. Qayyum, who has conducted field research studies on Bt cotton for about a decade now.