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Part II: 10 Years of Bt in India

Part II: 10 Years of Bt in India

Editor’s Note: This is the second of a three-part feature story on the history of Bt cotton in India. Part I appeared in Cotton International’s previous print issue (clickto view Part I). The third and final entry will appear in next week’s newsletter. Dr. Kehsav Kranthi is the director of India’s Central Institute for Cotton Research.

While there is a general perception that Bt cotton technology was singularly responsible for the dramatic improvement of cotton fortunes in India, it is pertinent to examine other probable factors that may have contributed to the higher yields.
One of them is imidacloprid, which was used as a seed treatment for protection against sap-sucking insects. Even a naïve student in India would know that none of the vast majority of Bt hybrids would have been able to sustain that onslaught of leaf hopper infestation without seed treated with imidacloprid. Gaucho, as it was known commercially, has been used in India since 2000 and was known to have contributed to at least 25% to 30% yield enhancement in the conventional hybrids, long before Bt cotton was introduced in the country.

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Since 2002, every Bt cotton seed has been treated with the highly effective insecticide, imidacloprid. Farmers have also been spraying the chemical on cotton crops to control leaf hoppers. Recently, leaf hoppers were found to have developed resistance to imidacloprid and therefore, crops can be damaged and yields are likely to decline due to sucking pests. The increase in yield may have also been due to other major changes, including the increase in cotton area in Gujarat from 1.5 M ha in 2000 to 2.6 M ha in 2009, increase in hybrid cotton area from 40% to 90%, introduction of six or seven new insecticide molecules for bollworm control and sucking pest management.

It is important to consider that maximum productivity gains were obtained from the 0.6 million to 0.7 million hectares of new area under cotton in Gujarat, which had the benefits of more than 100,000 newly constructed check dams apart from the highly fertile soils that were under groundnut cultivation for several years before cotton was taken up. New technologies such as pesticides with novel modes of action (imidacloprid, acetamiprid, thiomethoxam, spinosad, novaluron, ememectin benzoate, indoxacarb etc.) were introduced during 2001 and 2002.

Therefore, it is probable that the new pesticides, new hybrids, new micro-irrigation systems, new areas, and Bt-cotton together may have been effectively contributing to the enhanced rate of production and productivity. The role of Bt cotton in effectively protecting the crop from bollworms, especially the American Bollworm, Helicoverpa armigera, cannot be underestimated, but need not be overhyped either.

Currently, the main issue that worries stakeholders is the stagnation of productivity at an average of 500 kg lint per ha for the past seven years. The gains have been stagnant and unaffected by the increase in area of Bt cotton from 5.6% in 2004 to 85% in 2010.

The yield was 463 kg per hectare when the Bt cotton area was 5.6% in 2004 and reached a mere 506 kg per hectare when the area under Bt cotton increased to 9.4 M hectares at 85% of the total 11.1 M hectares.

Other concerns relate to the enhanced problems of sap-sucking insects such as leaf hoppers, aphids, whiteflies and thrips on the vast majority of susceptible Bt hybrids. New pathogens such as “leaf streak virus,” Myrothecium and Ramularia started affecting the new Bt hybrids. Insect populations of mealybugs, miridbugs, gall midges, mosquito bugs and safflower caterpillars, which were hitherto unknown as pests, suddenly emerged as concerns after the introduction of the new Bt-cotton hybrids.

This may have occurred due to the reduction in pesticide usage during the reproductive phase of the crop, which normally would have been used on conventional cotton.

Other factors that may have contributed to the sudden upsurge of these minor insect pests is that there are many Bt-cotton hybrids which are highly susceptible to these pests, apart from being susceptible to leaf reddening and wilt.