Bt Cotton Failure in Palakkad: Seed or Pest?
A farmer in Palakkad sows 4 hectares of a Bt cotton hybrid advertised as giving protection against American bollworm. He plants no refuge rows. By day 95, one 1-hectare block shows 55% boll damage, while his neighbour's non-Bt crop shows 70% damage. Pheromone traps catch mainly pink bollworm, not Helicoverpa. An ELISA on leaves from the damaged block gives a Cry1Ac signal in only 6 of 20 samples; a sample from the nursery block gives a signal in all 20. Seasonal rainfall was 35% above normal, and the field was sprayed twice with a pyrethroid. He has kept the empty seed packets but no laboratory report; the company's local dealer says the hybrid was tested only for the Cry1Ac gene. The farmer demands compensation, claiming the seed is spurious.
1. Does the evidence prove that the seed was spurious? Evaluate the ELISA result, the trap catch, the missing refuge and the spray history.
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The evidence does not prove that the seed was spurious. The nursery sample gave a Cry1Ac signal in all 20 samples, so at least some plants from the lot carried and expressed the construct. The damaged block gave a signal in only 6 of 20 samples, which could mean uneven seed lot, poor stand, or a fall in expression as the plants aged; Bt protein levels often decline late in the season.
The trap catch is more informative. Cry1Ac gives good control of Helicoverpa but not reliable control of pink bollworm, and the traps caught mainly pink bollworm. The 55% damage is therefore consistent with a pest that the technology was not claimed to control. The absence of refuge rows would accelerate selection of resistant insects. The pyrethroid sprays could have flared secondary pests rather than controlled the bollworm. A PCR test for the event and a quantitative ELISA, not damage alone, are needed to settle the seed claim.
2. Explain the refuge strategy and why its absence can make Bt cotton fail.
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Refuge rows are strips of non-Bt cotton planted nearby. They produce susceptible moths that can mate with any resistant survivors emerging from the Bt crop. The resulting offspring are heterozygous and, under a high-dose Bt crop, are unlikely to survive. This dilutes the frequency of resistance alleles in the population.
Without a refuge, resistant pink bollworm or bollworm survivors mate mainly with each other. Resistance then spreads rapidly through the local population. The farmer's field had no refuge at all, so the conditions favoured resistance. A refuge is not a cosmetic requirement; it is part of the resistance-management package that makes the technology last.
3. Recommend concrete steps for next season and specify what the seed company should provide to settle the dispute.
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Next season the farmer should use an approved hybrid with more than one insecticidal gene, plant the recommended non-Bt refuge, rotate with a non-host crop, monitor with pheromone traps, and destroy stubble after harvest to break the pink bollworm cycle. Sprays should be based on threshold counts, not fixed pyrethroid applications.
The company should provide the seed lot records, a PCR report confirming the event, and a quantitative ELISA from independent plants at several dates. Compensation is justified if the event is absent from the lot or if expression is far below the label claim; it is not justified by boll damage alone when the dominant pest is pink bollworm and no refuge was planted.