Role of transgenic Bt-crops in promoting biological control and integrated pest management
Since their commercial introduction in 1996 in the USA, the insect resistant transgenic Bt crops, notably Bt-cotton and Bt-corn, have given effective control of target pests and found overwhelming adoption in several countries. As of 2017, these Bt crops were cultivated in 14 countries on 100 m ha, including 11.4 m ha of Bt-cotton in India, which comprised 53% of 189.8 m ha of all GM crops grown in 24 countries. Such extensive cultivation of Bt crops, incorporated with genes derived from the soil bacterium, Bacillus thuringiensis (Bt), modified to express host-specific insecticidal crystalline (Cry) proteins, has resulted in higher crop yields by 22%, increased farmersâ€™ profit by 68% and reduced chemical insecticide applications by 37%, thereby providing social, economic, health and environmental benefits. The reduced chemical sprays have contributed to conservation of parasitoids and predators leading to enhanced biological control in crop systems. Feeding tests carried out with predators like ladybird beetles and green lacewing and also with hymenopteran parasitoids have demonstrated Bt proteins to be safe to these natural enemies. The value of Bt crops in promoting biological control and integrated pest management is discussed.
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