``If these insects feed on crop plants, obviously they are not useful insects because they could eventually destroy the crop. In fact, there is less danger (in genetically modified crops) than the use of sprays which may reach non-target crops through aerosols,'' he says. There have also been concerns that these crops may affect non-target organisms, which could lead tounforeseen and undesirable consequences. But according to Gopinath, the specificity of the biocide is well established. ``They (the biocide) don't affect non-target organisms. For that matter, it does not even affect other Lepidopteran species,'' he says. He therefore dismisses the fear that birds and non-target animals are in any kind of danger.

Says Dr T M Manjunath, one of the best entomologists in the country and a staunch proponent of IPM strategies for effective insect pest management in Indian crops, ``In most cases, the pests and their natural enemies belong to different orders of insects. Since Bt is specific in its action to a particular order (Coleoptera, Lepidoptera, Diptera, etc), the Bt used for the control of pests belonging to one order will not have an adverse effect on their natural enemies belonging to another order.''

He, however, adds that there are one or two reports indicating indirect effects on bio-control agents. But he asserts, ``Such effects are too marginal and not worthconsidering as long as we have achieved our primary objective of controlling the pests (the bio-control agents are also meant for this). A few beneficial organisms get killed even when we irrigate a crop. We cannot stop irrigation to save those few.''

Gopinath points out that the Bt toxin is a natural product made by the soil organism and that it is already present in the soil in small amounts and is easily biodegraded. The problems of accumulations, therefore, may not arise at all.

Discussing the potential of increased resistance among pests, Manjunath feels that there is a possibility that insects may develop resistance to Bt over the years. ``This is a natural phenomenon and therefore, we will be taking proactive measures to delay or prevent it by adopting Insect Resistance Management Strategies such as gene pyramiding, refuge crops, integrated pest management, etc, right from the beginning of the introduction of a Bt crop,'' he says.

Manjunath also points out that in the case of India particularly,there are so many alternate hosts for bollworms adjoining a cotton crop at a given point of time that the probability of onset of resistance becomes very low. In other words, resistance development will take far more time than otherwise.

Says Gopinath, ``Getting resistance development is a genetic event and a protein like Bt going to the genomic DNA of the target insect and mutating the DNA chances are extremely low.'' According to him, resistance here is mostly an adaptation phenomenon and is generally not transmitted to the next generation. To transfer resistance to the next generation, the mutation has to take place in the germ line. ``The probability is really low as compared to, say, the chemical pesticides, which are better mutagens,'' he adds.Manjunath explains that it is well known that pest insects feed on plants, while bio-control agents feed on pest insects and not on plants. ``Since Bt is incorporated in the plant, there is no possibility of the bio-control agents directly ingesting Bt,'' hepoints out.