Main pest develops resistance to Bt cotton
During field monitoring of the 2009 cotton crop in the state of Gujarat in western India, Monsanto1 and Mahyco scientists
detected unusual survival of pink bollworm to first-generation single-protein Bollgard cotton. Testing was conducted to assess for resistance to Cry1Ac, the Bt protein in Bollgard cotton, and pink bollworm resistance to Cry1Ac was confirmed in four districts in Gujarat – Amreli, Bhavnagar, Junagarh and Rajkot. Gujarat is one of nine states in India where cotton is grown. To date, no insect resistance to Cry1Ac has been confirmed outside the four districts in Gujarat.
This has been reported to the Indian Genetic Engineering Approval Committee (GEAC). Mahyco-Monsanto Biotech (MMB) in collaboration with the Central Institute of Cotton Research (CICR) and other agricultural research institutes have been conducting field monitoring research across India since 2003, the second season of Bt cotton in India.
Single-protein Cry1Ac products continue to control bollworm pests other than pink bollworm in the four districts in Gujarat where pink bollworm resistance has been confirmed. In addition, no instance of insect resistance in any of India's cotton growing states, including the four districts in Gujarat, has been
observed with Bollgard II, the second-generation Bt cotton technology. Bollgard II, introduced in 2006, contains two
proteins, Cry1Ac and Cry2Ab.
Current monitoring efforts to manage insect resistance by an Indian-expert network will be expanded. The network is led by the Director of CICR who is nominated by GEAC. The network will continue to conduct extensive insect monitoring, encourage appropriate stewardship practices such as proper refuge planting through an intensified farmer education campaign, and explore new methods of refuge seed delivery.
Resistance is natural and expected, so measures to delay
resistance are important. Among the factors that may have contributed to pink bollworm resistance to the Cry1Ac protein in Gujarat are limited refuge planting and early use of unapproved Bt cotton seed, planted prior to GEAC approval of Cry1Ac cotton, which may have had lower protein expression levels.
While single-protein Cry1Ac cotton products continue to deliver value to Indian farmers, increasingly Indian farmers are planting two-protein Bollgard II cotton because it reduces the need for insecticide sprays compared to Cry1Ac products and increases yield.
Over 65% of Gujarat cotton farmers chose Bollgard II
cotton in 2009, and pre-season bookings indicate that over 90% of Gujarat cotton farmers are expected to plant Bollgard II in the 2010 season. Overall, approximately 80% of all Indian cotton farmers are expected to plant Bollgard II in the 2010 season.
The findings in Gujarat are an important reminder to Indian farmers. When using Bt cotton products it is essential to regularly monitor and scout fields throughout the season for insect presence and plant appropriate non-Bt refuge. Furthermore, farmers must adopt measures such as need-based application of insecticide sprays during the crop season, and properly manage crop residue and unopened bolls after harvest. Examples of such practices include tillage and cattle grazing to minimize the survival and spread of pink bollworm.