Native Bacillus thuringiensis isolates against the old-world bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Ethiopia

ABSTRACT

Chickpea (Cicer arietinum L.) production in Ethiopia has been seriously constrained by the insect pest, Helicoverpa armigera. Insecticides have been used for decades to control this noxious pest. However, the restriction on chemical insecticides necessitates biological pest control alternatives. Therefore, the present study investigated the effectiveness of native Bacillus thuringiensis (Bt) isolates against Helicoverpa armigera 3rd instar larvae. The treatments consisted of Bt concentrations at the LD₉₀ values, whereas the control plots were sprayed with distilled water and a commercial Bt. var. thuringiensis product. The results revealed statistically (p < 0.05) significant differences between the native Bt isolates and the control plots. Post 1^st, pre 2^nd and post 2^nd Bt sprayed larval populations counted per plant ranged from 0.8 ± 0.3–3.1 ± 0.1, 0.6 ± 0.1–3.6 ± 0.0 and 0.5 ± 0.1–3.6 ± 0.4, respectively. Pod damage (%) and grain yield (t/ha) ranged between 9.7 ± 3.1 and 47.5 ± 9.5, 1.0 ± 0.0 and 2.6 ± 0.5, respectively compared to 47.5 ± 9.5% pod damage and 1.0 ± 0.0 (t/ha) grain yield from the control plots. These results indicate the potential of these bio-insecticides in the management of chickpea pod borer. Future research in Ethiopia should focus on additional collection, screening, characterisation, and testing in field trials.

KEYWORDS:

• Biological control
• crystal proteins
• LD₅₀
• larval mortality
• pod damage

Acknowledgements

The authors would like to thank Kulumsa Agricultural Research Center, EIAR and Gonde Basic Seed Farm Center, EABC for kind provision of all the necessary facilities and resources that include greenhouse and field experimental sites. The authors would like to extend their gratitude to Gallica Flower Farm for the generous provision of the reference Bt. var. thuringiensis. We would like to express our great pleasure to Mubark Mohammed and Dekaba Moges who supported us in fieldwork. The authors specially thank the Ethiopian Ministry of Education for partially funding this work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Authors contribution

LG, EG and DM perceived and carefully designed the experiment, LG prepared the materials, conducted the experiment, collected and analysed the data, prepared the first draft manuscript, EG supervised the work, interpreted results and figures, edited and revised the manuscript, DM provided guidance, interpreted results and figures, edited and revised the manuscript. All the authors read and approved the final manuscript submission.

Additional information

Funding

The work was partially funded by the FDRE Ministry of Education, Ethiopia.