Functional response of an egg parasitoid,Trichogramma chilonisIshii to sublethal imidacloprid exposure

Abstract

BACKGROUNDThe effectiveness of a biological control agent depends on how well it can control pests and how compatible it is with pesticides. Therefore, we reported the multigenerational effect of a commonly used insecticide, imidacloprid, on the functional response of a widely acclaimed egg parasitoid, Trichogramma chilonis Ishii, to different densities of the host Corcyra cephalonica Stainton eggs. The study investigated the outcomes of the median lethal concentration (LC50) and sublethal concentrations (LC5, LC30), along with control treatments for five continuous generations (F1 to F5).RESULTSThe results showed that the F5 generation of LC30, both of the F1 and F5 generations of LC50, and the control all had a Type II functional response. A Type I functional response was exhibited for the F1 generation of LC30 and both generations of LC5. The attack rate on host eggs treated with LC5 and LC30 did not change (decrease) with the shift in the type of functional response as compared to the control. A significant increase in the searching efficiency (a) was observed in the later generation (F5) under the exposure of LC5 and LC30 imidacloprid concentrations. A lower handling time (Th) in both generations of the LC5 followed by LC30 treated individuals was observed when compared with the control and LC50 treatments. The per capita parasitization efficiency (1/Th) and the rate of parasitization per handling time (a/Th) were also considerably higher in both the generations of LC5 and LC30 than in the control and LC50, thereby implying positive effects of imidacloprid on the parasitization potential of T. chilonis.CONCLUSIONAltogether, these multigenerational outcomes on the functional response of T. chilonis could be leveraged to control the intractable lepidopteran pests under the mild exposure of imidacloprid in integrated pest management (IPM) programs as well as in the mass rearing of the parasitoid, T. chilonis. © 2023 Society of Chemical Industry.

Partial exploitation of host egg patches resulting from a high rejection rate of healthy hosts cautions the mechanistic use of functional response models

“…How unlikely it is for a parasitoid not to encounter all hosts is quantitatively demonstrated in the present paper's Supplementary materials, Appendix 1. Similar results are commonly reported in studies that aimed to characterise the functional responses of parasitoids on immobile hosts (e.g., Jalali et al 2005;Reay-Jones et al 2006;Laumann et al 2008;Kasraee et al 2017;Mi et al 2022;Ray et al 2023).…”

“…Rather, the high rejection rate of healthy hosts indicates that functional response itself is changing over time in ways we do not yet understand. For example, published functional response studies typically used an experimental duration of one day or less (Mills and Lacan 2004; Jalali et al 2005; Reay-Jones et al 2006; Laumann et al 2008; Kasraee et al 2017; Mi et al 2022; Ray et al 2023). However, it is also possible to conduct the same experiment for different durations ( e.g., a few to several days).…”

“…Similar results are commonly reported in studies that aimed to characterise the functional responses of parasitoids on immobile hosts ( e.g ., Jalali et al 2005; Reay-Jones et al 2006; Laumann et al 2008; Kasraee et al . 2017; Mi et al 2022; Ray et al 2023).…”

The link between functional response and longevity of Trichogramma evanescens strains indigenous to Türkiye: A comparative assessment of parameters

“…Further challenges occur during decision-making process such as the employment of different statistical evaluation approaches for functional response types and associated parameters. For example, several studies used Hollings disc equation (Dong et al, 2017;Farrokhi et al, 2010;Kfir, 1983;Reay-Jones et al, 2006;Wang & Ferro, 1998;Yan et al, 2020) | 617 TONĞA Moezipour et al, 2008;Nikbin et al, 2014), and random predator (Ghaemmaghami et al, 2022;Ghorbani et al, 2019;Ray et al, 2023;Vaez et al, 2013) (Bruzzone et al, 2023). Similar differences can be encountered for type III functional response models (Ghaemmaghami et al, 2022;Vaez et al, 2013).…”

“…This is especially important considering various factors that influence their functional response characteristics and parameters. For example, previous studies revealed that either the functional response type or associated parameters of Trichogramma parasitoids are likely affected by biotic and abiotic factors such as, temperature, humidity, host density (del Pino et al, 2020;Moezipour et al, 2008), host species (Reay-Jones et al, 2006), host plants (Ghorbani et al, 2019), parasitoid density (Kfir, 1983), parasitoid age (Nikbin et al, 2014), and insecticides (Ray et al, 2023). Such factors are among the main drivers of intra-specific genetic variations that yields the occurrence of strains.…”