Abstract
BackgroundThe cotton leafworm, Spodoptera littoralis (Boisd.), is a serious economic pest in Egypt. Pest control depends mainly on chemical control with several pesticides include conventional and modern insecticides. Comprehensive analysis of pesticides impacts needs to investigate sublethal effects in addition to lethal effect.ResultsIn the current study, the leaf-dip bioassay method was used to evaluate emamectin benzoate (EMB) sublethal concentrations. Results showed that EMB proved high toxicity against S. littorals with LC50 value of 0.019 mg liter−1. Life table analysis showed that treatments with LC5 and LC15 prolonged larval period, mean longevity of males and females, mean generation time (T), doubling time (DT), adult preovipositional period (APOP), and total preovipositional period (TPOP) compared with control. On the contrary, net reproduction rates (R0), intrinsic rates of increase (r), finite rate (λ), fecundity, gross reproductive rate (GRR), and relative fitness were decreased compared to control.ConclusionsThe current study clarified that sublethal concentrations of EMB induce adverse effects and suppress the population growth of S. littorals. Our results would be useful to assess the overall effects of EMB on S. littorals and can contribute effectively in pest management.
Highlights
The cotton leafworm, Spodoptera littoralis (Boisd.), is a serious economic pest in Egypt
Insects and insecticides Laboratory colony of S. littoralis was reared in Central Agricultural Pesticides Laboratory (CAPL), Agricultural Research Center, Dokki, Giza, Egypt
The first larval instar of S. littoralis treated with LC5 and LC15 of Emamectin benzoate (EMB) showed a significant increase in the larval period compared with control
Summary
The cotton leafworm, Spodoptera littoralis (Boisd.), is a serious economic pest in Egypt. The cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae), is a key destructive polyphagous insect pest (Hosny et al 1986). This pest attacks several plant species belong to about 40 plant families (Pineda et al 2007). Several insecticides include emamectin benzoate were recommended to combat the pest (Egyptian Agricultural Pesticides Committee 2019). Sublethal amounts of pesticides can affect population growth parameters, feeding behavior, and insect bodies nutrient content (Rehan and Freed 2015; Xu et al 2016). Barrania (2019) clarified that treating 2nd instar larvae of S. littoralis with LC5 and LC10 of emamectin benzoate affected larval weights, larval duration, pupation, pupal mean weight, and adult emergence rates Sublethal amounts of pesticides can affect population growth parameters, feeding behavior, and insect bodies nutrient content (Rehan and Freed 2015; Xu et al 2016). Barrania (2019) clarified that treating 2nd instar larvae of S. littoralis with LC5 and LC10 of emamectin benzoate affected larval weights, larval duration, pupation, pupal mean weight, and adult emergence rates
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