The Hindu Business Line : Bollworm threat — Bt cotton may face pest trial this year

Test of efficacy
A dry spell after the recent rains followed by more rainfall could result in an outbreak of bollworm in Maharashtra and central India
With Bt cotton supposed to be capable of resisting the pest, this year could prove to be a test for it

New Delhi , Aug. 15

The current year could well test the efficacy of Bt cotton against the dreaded American bollworm pest.

According to Dr Keshav Raj Kranthi, senior scientist with the Nagpur-based Central Institute for Cotton Research's Crop Protection Division, conditions for bollworm infestation are most conducive "when you have good rainfall, followed by a prolonged dry phase and then it rains all over again."

This time around, the rain-fed cotton growing areas of Maharashtra and central India have received heavy monsoon rains during the first fortnight of August.

"There could be a problem if you now have a dry spell from say mid-August to mid-September and then another spell of rains. It would be the ideal scenario for an outbreak of bollworm (Helicoverpa armigera)," Dr Kranthi told Business Line.

The adult bollworm moths start laying eggs from mid-August in the north and during the first week of September in central India and mid-September in the south. The eggs take 2-3 days to hatch, after which the early stage larva begin feeding on the leaves till around the 14th day, when they pupate in the soil.

"They remain in the soil when there is drought. But once there are rains, the moths emerge out of the pupae and lay eggs all over again. And this time, the hatched larvae feed on the squares and green bolls, as by then the crop would have attained the flowering and fruiting stages," Dr Kranthi noted.

As far as Bt cotton is concerned, the claim is that it contains a gene derived from a soil bacterium, Bacillus thuringiensis (Bt) that synthesises a protein toxic to the bollworm insect.

The "expression" of the Bt protein is maximum in the leaves of the plant.

The early-hatched larvae feeding on the leaves perish before they reach the `third instar' or above stage, which means there is no possibility of new rounds of egg laying and larva feeding happening in the crucial fruiting and reproduction stages.

How these claims actually translate on the ground will probably be seen in the days to come.

More Stories on : Bio-tech & Genetics | Pests | Cotton

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