Bt cotton no match for Indian pests

Print edition : April 10, 2020

An Indian farmer spraying pesticide to his cotton field. Photo: Glenn Davis Stone/Washington University

A first long-term analysis of the impact of Bt cotton in India has found that production gains were due to changes in insecticide and fertilizer use and not the adoption of Bt cotton itself. The study has implied that the intrinsically produced insecticide (Cry toxin) by the transgenic cotton, which has the Bt gene genetically inserted, is not good enough to combat insects in the Indian context.

The analysis, published in the journal “Nature Plants”, is authored by Glenn Davis Stone, anthropologist at Washington University in St. Louis, and K.R. Kranthi, entomologist and the former director of India’s Central Institute for Cotton Research who is currently at the Washington-based International Cotton Advisory Committee. Genetically modified (GM) Bt cotton was introduced in India in 2002 and today accounts for 90 per cent of all cotton grown in the country. The apparent increased yields and reduced pesticides have been used to justify its large-scale cultivation. Bt cotton has been credited with tripling cotton production between 2002 and 2014. But the recent study dismisses the claim.

According to its authors, the production gains came before widespread seed adoption and must be viewed in line with changes in fertilization practices and pest population dynamics.

“Since Bt cotton first appeared in India there has been a stream of contradictory reports that it has been an unmitigated disaster, or a triumph,” Stone said, noting the characteristic deep divide in conversation about GM crops. “But the dynamic environment in Indian cotton fields turns out to be completely incompatible with these sorts of simplistic claims.” The earlier positive assessments were based on shorter time frames. The new study spans 20 years.

Stone said: “There are two devastating caterpillar pests for cotton in India. From the beginning, Bt cotton did control one of them, the American bollworm.... It initially controlled other one too, the pink bollworm, but that pest quickly developed resistance and is now a worse problem than ever. Bt plants were highly vulnerable to other insect pests that proliferated as more and more farmers adopted the crop.” “Yields in all crops jumped in 2003, but the increase was especially large in cotton. But Bt cotton had virtually no effect on the rise in cotton yields because it accounted for less than 5 per cent of India’s cotton crop at the time,” Stone pointed out.

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