Effect of Local Bacillus thuringiensis Isolates on Life Stages of Helicoverpa armigera (Hubner) and Spodoptera litura (Fabricus)

Author: Renuka D. Pawar, D.B. Undirwade, U.S. Kulkarni, M.P. Moharil, A.V. Kolhe and S.L. Borkar

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Abstract

The present investigation aimed to determine the impact of 11 Bt isolates native to Vidarbha region on biological parameters of H. armigera and S. litura larva which survived the dose of 1mg/ml and 2mg/ml respectively of crude Bt toxin from the isolates. It was evident from the study that even after surviving the given doses of Bt, some of the surviving larvae were unable to grow normally as compare to the larvae without any exposure to Bt toxins. It was recorded that local Bt isolate SY-4 adversely affects H. armigera among all the other isolates including standard Btk HD-1 recording maximum of 36.04, 86.67, 33.15 and 93.33 per cent reduction in larval weight, pupation, pupal weight and adult emergence respectively, similarly highest per cent reduction in fecundity and hatchability of 80.38 % and 45.34% respectively was recorded from pair in which both male and female survived the exposure of local isolate SY-4 during larval stage. In case of S. litura, local isolate SY-4 was found most effective among all the other isolates recording 29.79, 86.67, 60.48 and 93.33 per cent reduction on larval weight, pupation, pupal weight and adult emergence respectively. However SGd-1 adversely affected fecundity and hatchability of S. litura with 64.30 and 44.20 per cent reduction in fecundity and hatchabilty recorded from the pair in which both male and female were exposed to Bt during larval stage. It was evident from the present study that, local Bt isolates, SY-4 and SGd-1 were more potential not only causing mortality but also adversely affecting the normal biology of test insects which survived the exposure of these isolates.

Keywords

Bacillus thuringiensis, Bioassay, endotoxin, Helicoverpa armigera, Spodoptera litura

Conclusion

It was evident from the present investigations that all the 11 local Bt isolates have produced significant adverse effects such as reduction in larval and pupal weights, per cent pupation, adult emergence, fecundity and egg hatchability in larvae exposed to treated diet as compared to normal diet. From the data recorded under present study it can be concluded that, the larva of H. armigera and S. litura, surviving the Bt exposed diet, were further unable to grow normally and sustain. In case of H. armigera the isolate SY-4 has an equivalent effect as Btk HD-1 on adult emergence and it has more adverse effects on fecundity and hatchability of H. armigera than Btk HD-1. In case of S. litura, the isolate SY-4 was found equally effective as standard Btk HD-1 in terms of reduction in adult emergence However, the isolate SGd-1 was found to be more potent than the standard strain Btk HD-1 in terms of reduced fecundity and hatchability of S. litura. It was evident from the studies that exposure of larva to Bt during larval stage also have pronounced effects on reproductive capabilities of both male and female members. However the effects were more predominant in female members of both H. armigera and S. litura.

References

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How to cite this article

Renuka D. Pawar, D.B. Undirwade, U.S. Kulkarni, M.P. Moharil, A.V. Kolhe and S.L. Borkar (2022). Effect of Local Bacillus thuringiensis Isolates on Life Stages of Helicoverpa armigera (Hubner) and Spodoptera litura (Fabricus). Biological Forum – An International Journal, 14(4): 961-968.