Original paper
Screening of Highly Toxic Bacillus thuringiensis and its Effects on the Growth and Development of Spodoptera exigua (Lepidoptera: Noctuidae)
Yang, Xiaolin;Oluwafemi, Akinkurolere Rotimi;Zhang, Hongyu
published: 7/25/2008
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ArtNo.: ESP146003101009
Abstract
In this study,the toxicity of Bacillus thuringiensis YL- 17 to Spodoptera exigua (Hübner 1808) was screened from 23 stock B thuringiensis isolates. Its lethal and sublethal effects on the development and mortality of S exigua were evaluated,and the LC 50 values were determined. The LC 50 s of pure crystals, pure spores and the spore-crystal complex were 22.1 µg/ml,230.2 µg/ml and 20.2 µg/ml,respectively. The toxicity of B thuringiensis YL- 17,stemmed mainly from its crystal.B thuringiensis YL- 17 did not affect the hatch rate of eggs, but the neonate mortality increased significantly (P< 0.05 ) with an increase of treatment concentration and egg age. The spore-crystal complex significantly (P< 0.05 ) inhibited the growth of the third instar larvae, significantly (P< 0.05 ) extended the larval development, and caused a significant (P< 0.05 ) reduction in the weight of pupae, the pupation rates and the adult emergence rates of larvae that survived. However, there was no significant effect of the spore-crystal complex (P= 0.18 ) on adult sex ratio of larvae that survived. These results suggest that besides killing S exigua larvae, B thuringiensis YL- 17 also influences the development of larvae and pupae of this pest.
Keywords
Bacillus thuringiensis Spodoptera exigua (Hübner 1808) • sublethal effects • AKINKUROLERE RO