Contents - Faperta

Deployment of Insect-Resistant Transgenic Crops for Pest Management 327
where there was no diamondback moth infestation, and 1.1 to 12.8 in plots where there
was diamondback moth infestation. No competitive advantage was observed for either
plant type in seed mixtures when there was no diamondback moth infestation. Moth densities
in all plots (mixed and nonmixed) declined after two generations (Riggin Bucci and
Gould, 1997). Percentage of parasitism by the parasitoid, Diadegma insulare (Cresson) was
not signifi cantly different between mixed and nonmixed plots, and abundance of the four
most common diamondback moth, P. xylostella, predators did not differ between mixed
and nonmixed plots. There were no differences in numbers of predators on transgenic
versus nontransgenic plants. Intrafi eld mixtures may decrease the density of target pests
such as the diamondback moth, while not adversely affecting the natural enemies.
Therefore, there is considerable potential for integration of transgenic plants and cultural
practices for IPM.
Advantages and Limitations of Insect-Resistant Transgenic Crops
There will be tremendous potential benefi ts to the environment through the deployment
of genetically modifi ed crops. Deployment of insect-resistant crops has been estimated to
result in a one million kilogram reduction in pesticides applied for pest control in the
United States in 1999 as compared to 1998 (NRC, 2000). Papaya with transgenic resistance
to ringspot virus (Gonsalves, 1998) has been grown in Hawaii since 1996. Rice yellow mottle
virus (RYMV), which is diffi cult to control with conventional approaches, can now be
controlled through transgenic rice, which will provide insurance against total crop failure.
Globally, herbicide-resistant soybean, insect-resistant maize, and genetically improved
cotton account for 85% of the total area under transgenic crops. Transgenic plants with
insecticidal genes are set to feature prominently in pest management in both developed
and the developing world in future. Such an effort will play a major role in minimizing
insect-associated losses, increase crop production, and improve the environment. Brookes
and Barfoot (2005) have estimated that use of genetically modifi ed crops has led to a
decrease in pesticide use by 172,000 metric tons, reduction in greenhouse gas emissions by
10 million metric tons, diesel fuel savings by 1.8 billion liters, increase in net income for
farmers by $27 billion ($4.16 billion in China and $124.2 million in India), reduced environmental
index quotient (EIQ) by 14%, and generated global market of biotech crops by $5.5
billion in 2006. Major advantages of growing transgenic crops are:
• A major reduction in insecticide sprays;
• Increased activity of natural enemies;
• Reduced exposure of nontarget organisms to pesticides; and
• Reduction in pesticide residues in food and food products.
The benefi ts of growing transgenic crops to growers have been higher yield, lower input
costs, and easier agronomic management. These factors are likely to have substantial
impact on the livelihoods of farmers in both developed and developing countries. However,
there is considerable public debate on the issue, and several claims to the contrary have also
been published. In many developing countries, small-scale farmers suffer pest-related yield
losses because of technical and economic constraints. Pest-resistant genetically modifi ed