Elsevier

Crop Protection

Volume 167, May 2023, 106211
Crop Protection

Adverse impacts of development on the deltamethrin-exposed host Ephestia elutella (Lepidoptera: Pyralidae) on population parameters of Habrobracon hebetor (Hymenoptera: Braconidae)

https://doi.org/10.1016/j.cropro.2023.106211Get rights and content

Highlights

  • Low lethal concentrations of deltamethrin significantly lowered the preadult survival rate of H. hebetor.

  • Low lethal concentrations of deltamethrin significantly reduced the life table and the paralysis rate parameters of H. hebetor.

  • Deltamethrin should be applied judiciously when using H. hebetor to control E. elutella.

Abstract

Habrobracon hebetor (Say) (Hymenoptera: Braconidae) is a widely distributed parasitoid that can be used to control numerous lepidopteran pests including Ephestia elutella (Hübner) (Lepidoptera: Pyralidae). The present study was aimed to evaluate the indirect impacts of deltamethrin on the life table parameters and the paralysis rate parameters of H. hebetor using the age-stage, two-sex life table method under laboratory conditions. The results indicated that the preadult survival rate of H. hebetor was significantly reduced (with LC5 and LC10 values of 0.41 and 0.49, respectively) in insecticide-treated populations. Similarly, after low-concentration (LC5 and LC10) treatments with the insecticide, the values of three important life table parameters (i.e., intrinsic rate of increase [r], finite rate of increase [λ], and net reproductive rate [R0]), and two major paralysis rate parameters (i.e., net paralysis rate [C0], and finite paralysis rate [ω]) of H. hebetor were significantly decreased compared to the control group. However, these parameters were not significantly different between the LC5 and LC10 treatment groups. Our results demonstrated that low lethal concentrations of deltamethrin can significantly depress the performance of H. hebetor. In order to establish an effective integrated pest management program to control E. elutella, it will be necessary to determine the adverse effects of deltamethrin on H. hebetor under warehouse conditions.

Introduction

Flue-cured tobacco is a cash crop grown in many parts of the world, including in China. The tobacco or warehouse moth, Ephestia elutella (Hübner) (Lepidoptera: Pyralidae), is a primary stored product pest in tobacco warehouses (Ashworth, 1993; Wang et al., 2021). In addition to the direct effects that larval feeding has on tobacco leaves, their excreta and web production further reduce the quality of stored tobacco (Deng et al., 2018; Wang et al., 2021).

Contact insecticides such as the pyrethroid deltamethrin are highly efficacious against the larvae of E. elutella (Yuan et al., 2020). Other widely used control measures are fumigants, including aluminum phosphide (Bell, 1979, 1992; Yuan et al., 2020; Wang et al., 2021). Although they are effective and quick-acting, their use involves several downsides including the risk of fire, corrosion of metal equipment, development of pesticide resistance, negative impacts on natural enemies and the environment, and harmfulness to human health (Ou et al., 2021a). Biological control agents have received increased attention in the management of E. elutella to minimize the application of insecticides and fumigants (Ou et al., 2019, 2021a, 2021b; Pezzini et al., 2020; Wang et al., 2021).

The widely distributed braconid wasp, Habrobracon hebetor (Say) (Hymenoptera: Braconidae), is a gregarious and idiobiont ectoparasitoid wasp attacking lepidopteran larvae (Jervis et al., 1994; Işitan et al., 2011; Ou et al., 2019). In stored products, H. hebetor is generally considered to be one of the most effective biocontrol agents using mass releases against lepidopteran pests, including E. elutella, due to its characteristics such as rapid population growth, short preadult stage, prolonged adult lifespan, high reproductive rate, high paralysis rate, and the fact that adult individuals can remain active in certain conditions (e.g., winter) (Sanower et al., 2018; Ou et al., 2019, 2021a, 2021b; Gowda et al., 2021). Female wasps paralyze by injecting venom through the cuticle of the host and then lay eggs on or near the surface of the immobilized larvae (Antolin et al., 1995). In general, the number of hosts paralyzed by the H. hebetor (paralysis rate) is higher than the number of parasitized hosts (parasitism rate). Paralysis is always fatal (Ou et al., 2021b), and thus the paralysis rate is used to measure the host attack capability of H. hebetor (Ou et al., 2019). To date, there have been several reported cases on the successful use of H. hebetor alone against lepidopteran pests in warehouses and fields (Castañé et al., 2018; Amadou et al., 2019).

In integrated pest management (IPM) programs, pest control accomplished with natural enemies (e.g., parasitoids and predators) often requires supplemental application(s) of chemical or organic pesticides (de Paiva et al., 2018; Parreira et al., 2018). Ideally, when combined with biocontrol agents, the pesticide used should not adversely affect non-target natural enemies (Khan et al., 2015) or compromise each other's effectiveness (Torres and Bueno, 2018). Unfortunately, non-target natural enemies are often equally or are more susceptible to pesticides than the targeted pest. Therefore, appraisal of the sensitivity of non-targeted insects to the insecticides being employed is necessary when those pesticides are being considered for use in IPM programs (Saber and Abedi, 2013; Abedi et al., 2014). In general, the evaluation methods for such studies have been concerned primarily with lethal and sublethal effects of insecticides on natural enemies (Desneux et al., 2007; Guedes et al., 2016). The sublethal effects of an insecticide on a natural enemy can include decreasing their survival rate, developmental period, and values of reproductive parameters, and even influencing their behavior responses (Rafiee-Dastjerdi et al., 2012; Saber and Abedi, 2013; Jarrahi and Safavi, 2016). These effects are frequently observed under field conditions.

Direct exposure to lethal and sublethal doses of pesticide have been shown to affect the demographic parameters of H. hebetor (Mahdavi and Saber, 2011; Saber and Abedi, 2013; Rezaei et al., 2020). However, to the best of our knowledge, no published data are available concerning whether H. hebetor incurs indirect effects after developing on E. elutella treated with sublethal doses of deltamethrin. The objectives of this study were to expose host E. elutella larvae to two low lethal concentrations of deltamethrin and then evaluate the life table parameters and paralysis rate parameters of H. hebetor using the age-stage two-sex life table procedure. Our results will help estimate population-level effects and determine the compatibility of deltamethrin and H. hebetor in IPM programs for tobacco warehouses.

Section snippets

Insect cultures

The E. elutella colony was established using larvae originally collected from a tobacco warehouse at the Guizhou Provincial Tobacco Company (26°52′ N, 106°73′ E; 1120 m altitude) in 2016. Larvae were fed on an artificial diet as described in our previous studies (Ou et al., 2019; Wang et al., 2021). The colony was maintained in a climate chamber (RXZ-380A-LED, Ningbo Jiangnan Instrument Factory, Ningbo, Zhejiang, China) at 28 ± 1 °C, RH 75 ± 5%, and a photoperiod of 16 h: 8 h (L: D). The

Toxicity of deltamethrin on E. elutella larvae

The acute toxicity of deltamethrin on 5th instar larvae of E. elutella 48 h after contact with treated tobacco leaves is shown in Table 1. The regression equation was y = 1.9864x - 5.2065 [y is the expected probit mortality, x is log10 (concentrations of deltamethrin)] (χ2 = 1.14). The LC5 and LC10 values for E. elutella were 51.90 and 79.08 mg/L, respectively. Mortality was not observed in the control group.

Life table of H. hebetor developing on E. elutella after treatment with low lethal concentrations of deltamethrin

The mortality of H. hebetor on host larvae increased significantly with increasing

Discussion

Pesticide residues are important sources of potentially lethal exposure for predaceous and parasitic insects. This is especially true in parasitoid wasps (Müller, 2018; Suárez-López et al., 2020). To realistically simulate the indirect effects of insecticide on natural enemies, we introduced male and female wasps to E. elutella larvae that had been exposed to low lethal concentrations (LC5 and LC10) of deltamethrin. Our study demonstrated that there was a significant decrease in the survival

Conclusion

In conclusion, this study determined that changes in the life table and paralysis rate parameters of H. hebetor were due to the low lethal effects caused by indirect exposure to deltamethrin. The results showed that even a low lethal concentration of deltamethrin could indirectly affect the population performance of H. hebetor and should, therefore, be applied judiciously when using H. hebetor to control E. elutella.

Funding

This study was supported by the Guizhou Province Science and Technology Innovation Talent Team Project (Qian Ke He Pingtai Rencai-CXTD [2021] 004); the Research Fund for Postgraduates of Guizhou, Guizhou, China (YJSCXJH [2019]107); the Science and Technology Project of Guiyang Branch Company of Guizhou Tobacco Company (2019–03).

Author contributions

Xiu-Qin Wang: Conceptualization, Methodology, Formal analysis, Writing-Original draft.

Hou-Ding Ou: Methodology, Writing the manuscript.

Hao-Xi Li: Review and Editing.

Lan Wei: Methodology, Formal analysis.

Yao Huang: Methodology, Formal analysis.

Mao-Fa Yang: Supervision, Funding acquisition, Project administration, Writing-Review and Editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

We thank Professor Hsin Chi (National Chung Hsing University, Taichung, Taiwan) for his patient guidance using the TWOSEX-MSChart program. We are extremely grateful to Dr. Cecil L. Smith (University of Georgia, USA), the Charlesworth Group (https://www.cwauthors.com/) and TopEdit (http://topeditsci.com) for the English editing of this manuscript. We are also grateful to the contributions of the editor and three anonymous reviewers for their useful comments and suggestions, which helped in

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