Lethal and sub-lethal effects of spinosad on the life-history traits of army worm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), and its fitness cost of resistance
2015
Rehan, A., Bahauddin Zakariya University, Multan, Pakistan | Freed, S., Bahauddin Zakariya University, Multan, Pakistan
Spodoptera litura is one of the most destructive polyphagous insect pests, with more than 120 host-plant species. In our present study, a field-collected population of S. litura when selected with spinosad for 11 consecutive generations resulted in the development of 3921-fold resistance to spinosad as compared to the susceptible strain. The spinosad-resistant strain of S. litura had a relatively high fitness cost (0.17) as compared to the susceptible strain. Furthermore, the lethal and sub-lethal effects of different concentrations of spinosad were checked on the susceptible strain at different levels; i.e., LC 40 ,LC 30 ,LC 20 and LC 10 , which revealed that the impact of spinosad on the life-history traits of S. litura increased with the increase in concentration of spinosad. A significant impact of spinosad was recorded on the larval duration, pre-pupal weight, pupal duration, pupal weight, reproductive potential and adult emergence. The outcomes of the current research clearly indi- cate that fitness cost of spinosad and its sub-lethal effects have a significant impact on population dynamics of S. litura, for which it can be incorporated in integrated pest management.
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