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.
Highlights
Among insect pests of cultivated crops, polyphagous insects are most devastating due to the benefit of having alternate refuges to escape from applied management strategies
The results indicate that when S. exigua population switches its host from castor to auxiliary hosts, no significant difference in efficacy of insecticides, in terms of percent mortality of the larvae, was observed (F12,100 = 1.518, p = .13)
Maximum increase was observed when the larvae shifting from okra to cotton and spinach were treated with cypermethrin and lufenuron while percent mortality decreased by 25% and 15% when the larvae switched hosts to castor and cotton and treated with chlorpyrifos and emamectin benzoate, respectively (Figure 4g)
Summary
Among insect pests of cultivated crops, polyphagous insects are most devastating due to the benefit of having alternate refuges to escape from applied management strategies. Despite having a range of robust and effective insecticides to be used against S. exigua (Ahmad, Arif, & Ahmad, 2007; Antwi & Peterson, 2009), we are unable to control this pest in most of the scenarios Cosmopolitan distribution of this pest on several cultivated crops and indiscriminate use of broad spectrum insecticides (An, Orellana, Phelan, Cañas, & Grewal, 2016; Armstrong, Abdel-Mageed, Fokar, Allen, & Adamczyk, 2013) has resulted in the development of insecticide resistance (Sayyed, Ahmad, & Saleem, 2008). The effect of host switching (utilizing different plant species by progeny of subsequent generations during population buildup and moving on to the primary host during the same cropping season) by polyphagous pest on their susceptibility to chemical control has seldom been explored. Our study will help in clearly understanding the role of host plants in resistance management of major phytophagous insect pests and their ecology
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.