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VOL. 11, ISSUE 1 (2026)
Impact of transgenic Bt cotton hybrids expressing Cry1Ac and Cry2Ab endotoxins and non-Bt on biological attributes of American bollworm, Helicoverpa armigera (Hubner)
Authors
Harish Kumar, Ram Singh
Abstract
The American bollworm, Helicoverpa armigera (Hubner)
(Lepidoptera: Noctuidae), is a destructive pest of cotton causing substantial
yield losses. The deployment of Bt cotton expressing Cry1Ac toxin provided
effective control; however, its limited spectrum and declining efficacy with
crop age necessitated the development of dual-gene Bollgard II (Cry1Ac +
Cry2Ab) hybrids. The present investigation evaluated the age-specific efficacy
and persistence of Bt, non-Bt, and BG II cotton hybrids against third instar larvae
of H. armigera under laboratory conditions at CCS HAU, Hisar, India.
Leaves, squares, and bolls were collected at 85, 125, and 145 days after sowing
(DAS) from six hybrids and assessed for their impact on larval survival,
duration, weight, pupation, pupal period, and adult emergence. Results revealed
that BG II hybrids recorded significantly lower larval survival, larval weight,
pupal weight, and adult emergence compared to Bt and non-Bt hybrids
across all crop stages. At 85 DAS, complete larval mortality was observed on BG
II plant parts, whereas survival increased at later stages (125 and 145 DAS),
indicating a decline in toxin efficacy with crop maturity. Larval and pupal
durations were prolonged on BG II hybrids, reflecting growth inhibition effects.
In contrast, non-Bt hybrids consistently supported higher survival, faster
development, and greater adult emergence. The findings demonstrate the superior
efficacy of BG II hybrids over single-gene Bt cotton, although a gradual
reduction in effectiveness with advancing crop age was evident. These results
highlight the importance of monitoring toxin persistence and adopting
integrated pest management strategies for sustainable control of H. armigera
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Pages:435-439
How to cite this article:
Harish Kumar, Ram Singh "Impact of transgenic <i>Bt </i>cotton hybrids expressing Cry1Ac and Cry2Ab endotoxins and non-<i>Bt</i> on biological attributes of American bollworm, <i>Helicoverpa armigera</i> (Hubner)". International Journal of Entomology Research, Vol 11, Issue 1, 2026, Pages 435-439
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