Efficacy of Hypoxia Against Tribolium castaneum (Coleoptera: Tenebrionidae) Throughout Ontogeny

Abstract

Hermetic grain storage technology offers a viable chemical-free approach to control storage insects. However, there is limited knowledge on how hypoxia affects the survival of insect life stages during grain storage in hermetic bags. We exposed Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) eggs (2 d), young larvae (7 d), old larvae (21 d), pupae (28 d), and adults (2 d after emergence) to 2, 4, 8, and 20.9% oxygen levels for 1, 3, 5, 10, and 15 d and assessed subsequent mortality. At 2% oxygen, complete mortality was achieved in 3 d for eggs and young larvae, 10 d for old larvae and pupae, and 15 d for adults. At 4% oxygen, 15 d were required to kill all eggs and old larvae but not the other insect life stages. At 8% oxygen after 15 d, complete mortality of any insect life stage was not observed; but even a relatively short exposure (1–3 d) caused significant developmental delays in immature insects. Our study shows potential utility of hermetic technology for control of T. castaneum , but internal oxygen should be maintained below 2% level for at least 15 d for complete control. Increased oxygen levels improved the development of all insect life stages leading to increased adult emergence. There is a need to explore exposure time required to achieve complete mortality of all insect life stage above the 2% oxygen level.

Effects of Hypoxia on Acoustic Activity of Two Stored-Product Pests, Adult Emergence, and Grain Quality

“…Assessment immediately after exposure to hypoxia treatments for 14 d revealed no adult S. oryzae survived. These findings are in agreement with results of Kharel et al (2019) who showed that exposure of T. castaneum to 2% or less for 15 d resulted in no adult survival. However, exposure to higher oxygen levels such as 4 and 8% did not result in complete mortality.…”

“…Furthermore, our results showed no adult emergence from 1% oxygen level after 45 d post-treatment. This result corroborates previous findings that show exposure of C. maculatus and T. castaneum eggs to oxygen levels below 2% causes up to 100% egg mortality (Cheng et al 2012, Kharel et al 2019). Though 3 and 5% resulted in a few live adults 45 d post-treatment, they might have affected the development of the insects.…”

“…Hypoxia treatments eliminated acoustic activity of both insect species over a similar time range probably because they have similar oxygen-dependent physiological processes. Kharel et al (2019) showed that the time required to kill adult T. castaneum (Coleoptera: Tenebrionidae) under controlled environment varied with hypoxia treatments: 2 and 4% oxygen levels achieved complete and 90% mortality, respectively, in 15 d. Under hermetic storage conditions, however, the time required to kill insects depends on how fast oxygen is depleted. Oxygen depletion is determined by several factors including level of infestation, initial quantity of oxygen available, and environmental conditions such as temperature and RH.…”

“…Though 3 and 5% resulted in a few live adults 45 d post-treatment, they might have affected the development of the insects. Kharel et al (2019) showed that adult developmental time was increased by 18 and 15 d when was young larvae of T. castaneum were exposed 4 and 8% oxygen levels, respectively. Carli et al (2010) showed complete inhibition of progeny development when Sitophilus spp.…”

The Orphan Cytokine Receptor CRLF3 Emerged With the Origin of the Nervous System and Is a Neuroprotective Erythropoietin Receptor in Locusts

“…As documented for many species from different orders, insects achieve extraordinary resistance to hypoxia by switching to anaerobic metabolic pathways and reduction of basal metabolic rates amongst other adaptations (reviewed by Hoback and Stanley, 2001). Hypoxia tolerance has also been reported for locusts (Arieli and Lehrer, 1988; Wegener and Moratzky, 1995; Greenlee and Harrison, 2004) and T. castaneum (Donahaye, 1990; Kharel et al, 2019), the two species in which CRLF3-mediated neuroprotection has been demonstrated. In comparison to mammalian neurons, where rather brief hypoxic episodes are sufficient to induce apoptosis, survival of locust and beetle neurons in vitro decreases only 20–30% even when challenged by prolonged (36 h) and severe (<0.3% oxygen) hypoxia (this study; Miljus et al, 2014; Hahn et al, 2017).…”