Switching among natal and auxiliary hosts increases vulnerability of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) to insecticides

Abstract

The role of insecticidal application and host plant resistance in managing Spodoptera exigua has been well documented, but the effect of different host plants, on which the pest cycles its population in the field, has seldom been investigated. Therefore, we have studied the vulnerability of S. exigua against commonly used insecticides (cypermethrin, chlorpyrifos, lufenuron, and emamectin benzoate) with different mode of actions when it switches its generations from natal to auxiliary hosts and vice versa. Different field populations being established on different host plants including castor, cauliflower, cotton, okra, and spinach were collected and reared in the laboratory before insecticidal bioassays. The role of larval diet and host plant switching on their response to tolerate applied insecticides was studied using leaf‐dip bioassay methods. Host switching demonstrated a significant role in altering the vulnerability of S. exigua populations to tested insecticides. Spodoptera exigua sourced from castor, when switched host to okra and spinach, exhibited 50% higher mortality when treated with emamectin benzoate. This trend in mortality was consistent upon complete host switch cycle (natal—auxiliary—natal host). However, the highest increase (92%) in vulnerability was recorded when the larvae were shifted to spinach from cotton. In general, chlorpyrifos and lufenuron had highest efficacies in terms of larval mortality. The findings of present studies provide insights to a better understanding the behavior of polyphagous pests and the role of different host plants in altering the susceptibility of these pests against applied insecticides. Ultimately the results warrant that due consideration should be given to cropping patterns and time of host switching by pest population during planning and executing chemical control.

Knockdown of CYP9A9 increases the susceptibility to lufenuron, methoxyfenozide and a mixture of both in Spodoptera exigua

“…IGRs play a pivotal role in the control of S. exigua , a polyphagous pest of economically important crops (Ishtiaq et al, 2012). S. exigua is, nevertheless, resistant or tolerant to many IGRs, such as MET and LUF (Ishtiaq & Saleem, 2011; Osorio et al, 2008; Saeed et al, 2017; Wang et al, 2021). In our previous study, MML had increased insecticidal toxicity and sublethal effects in S. exigua larvae (Chen et al, 2019).…”

“…Spodoptera exigua (Lepidoptera, Noctuidae) is a prevalent polyphagous pest and has evolved resistance to LUF and MET (Enriquez et al, 2010; Mosallanejad et al, 2008; Moulton et al, 2002; Nakagawa et al, 2002; Saeed et al, 2017; Smagghe et al, 2003), which is possibly associated with overexpression of CYP3 clade (Hafeez et al, 2019; Hafeez et al, 2020a,b; Hu et al, 2021; Wang et al, 2018; Zhao et al, 2015; Zuo et al, 2021) and oxidative metabolism activity (Chen et al, 2019). Despite the detection of field populations of either LUF/MET tolerant or resistant S. exigua connections between LUF/MET actions and CYP3 clade remain poorly understood (Ishtiaq & Saleem, 2011; Osorio et al, 2008; Saeed et al, 2017; Wang et al, 2021).…”

Spodoptera frugiperda (JE Smith) in India: Pervasiveness, Host Range, and Management

“…According to Bortolotto et al (2014), in countries with tropical climates and the practice of multiple cropping systems, such as India, polyphagous pests like FAW exhibit a notable ability to adapt swiftly to new agro-ecosystems . In these areas, the "green bridge effect" enables pests to continue thriving even when their preferred hosts are not present, causing frequent pest outbreaks across a wide range of agricultural and climatic conditions (Kennedy and Storer 2000, Pedigo 2002, Saeed et al 2017. This phenomenon has the potential to elevate secondary polyphagous pests to the status of "key pests," a term used to describe pests that can have substantial economic implications (Pedigo 2002).…”

Fitness and cold tolerance of Spodoptera frugiperda fed on corn and two winter crops

“…If FAW can complete its life cycle on cabbage or rape in some regions where the optimal host (corn) is rarely or not planted in winter, these regions might become the winter breeding area for FAW, which would provide a large number of pest resources for migration in the next year. Furthermore, whether host switching in winter, like other insect species, can improve FAW cold tolerance to help this pest's overwintering (Saeed et al., 2017)? Based on these scientific gaps, this study describes the oviposition preference, feeding preference, developmental parameters and cold tolerance of FAW fed on corn, cabbage and rape, which will benefit to forecast of the winter breeding area and population dynamics of FAW.…”