Toxicity and neurophysiological impacts of plant essential oil components on bed bugs (Cimicidae: Hemiptera)

Sudip Gaire,Michael E Scharf,Ameya D Gondhalekar

doi:10.1038/s41598-019-40275-5

Abstract

Bed bugs (Cimex lectularius L.) are globally important human parasites. Integrated pest management (IPM) approaches, which include the use of essential oil-based insecticidal compounds, have been proposed for their control. This study aimed to define insecticidal activity and neurophysiological impacts of plant essential oil constituents. The topical and fumigant toxicity of 15 compounds was evaluated against adult male bed bugs. Neurological effects of the 6 most toxicologically active compounds were also determined. In both topical and fumigant bioassays, carvacrol and thymol were the most active compounds. The potency of bifenthrin (a pyrethroid insecticide) in topical bioassays was 72,000 times higher than carvacrol, while vapors of dichlorvos (an organophosphate insecticide) were 445 times more potent than thymol. Spontaneous electrical activity measurements of the bed bug nervous system demonstrated neuroinhibitory effects of carvacrol, thymol and eugenol, whereas linalool produced an excitatory effect. Although citronellic acid and (±)-camphor increased baseline activity of the nervous system their effects were not statistically significant. Bifenthrin also caused neuroexcitation, which is consistent with its known mode of action. These comparative toxicity and neurological impact findings provide new information for formulating effective essential oil-based insecticides for bed bug IPM and conducting mode-of-action studies on individual essential oil components.

Highlights

Bed bugs (Cimex lectularius L.) are economically and medically important global human parasites
Acetone-diluted essential oil components were applied to the ventral metathorax of adult male bed bugs to determine their topical toxicity
We characterized the inherent toxicity of fifteen different plant essential oil components against bed bugs

Summary

Introduction

Bed bugs (Cimex lectularius L.) are economically and medically important global human parasites. Plant-derived essential oils have emerged as a potential alternative option for the management of insect pests[15,16]. Recent studies have shown that plant-derived essential oils exhibit contact and fumigant toxicity against field populations of bed bugs[14,19,20]. There is a need for conducting comparative baseline toxicity studies with bed bugs using major components or constituents of different plant essential oils (Table S1) that have been shown to be efficacious against urban and agricultural insect pests[22,23,24,25,26,27,28,29,30,31]. Recent in silico molecular docking studies with major chemical constituents of marigold essential oil (α-terpinolene, piperitone and piperitenone) suggested the neurotransmitter hydrolyzing enzyme acetylcholinesterase as the potential target site in bed bugs[14]

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