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Ethyl formate and phosphine fumigations on the two-spotted spider mite, Tetranychus urticae and their biochemical responses

Kim, Kyeongnam, Lee, Yong Ho, Kim, Gayoung, Lee, Byung-Ho, Yang, Jeong-Oh, Lee, Sung-Eun
Applied biological chemistry 2019 v.62 no.1 pp. 50
H+/K+-exchanging ATPase, H-transporting ATP synthase, NADH dehydrogenase, Tetranychus urticae, acaricide resistance, acaricides, acetylcholinesterase, adults, biomarkers, cytochrome-c oxidase, eggs, electron transport chain, enzyme inhibition, exposure duration, flavoproteins, formates, fumigants, fumigation, gene expression regulation, genes, insects, lethal concentration 50, methyl bromide, nymphs, organobromine compounds, pests, phosphine, quarantine, toxicity
Two spotted spider mite, Tetranychus urticae, is a polyphagous pest to a variety of plants and they are hard to be controlled due to occurrence of resistance to acaricides. In this study, biochemical evaluation after ethyl formate (EF) and phosphine (PH₃) fumigation towards T. urticae might help officials to control them in quarantine purposes. PH₃ fumigation controlled eggs (LC₅₀; 0.158 mg/L), nymphs (LC₅₀; 0.030 mg/L), and adults (LC₅₀; 0.059 mg/L) of T. urticae, and EF effectively affected nymphs (LC₅₀; 2.826 mg/L) rather than eggs (LC₅₀; 6.797 mg/L) and adults (LC₅₀; 5.836 mg/L). In a longer exposure time of 20 h, PH₃ fumigation was 94.2-fold more effective tool for control of T. urticae than EF fumigant. EF and PH₃ inhibited cytochrome c oxidase (COX) activity differently in both nymphs and adults of T. urticae. It confirmed COX is one of target sites of these fumigants in T. urticae and COX is involved in the respiratory chain as complex IV. Molecular approaches showed that EF fumigation completely down-regulated the expression of cox11 gene at the concentration of LC₁₀ value, while PH₃ up-regulated several genes greater than twofold in T. urticae nymphs treated with the concentration of LC₅₀ value. These increased genes by PH₃ fumigation are ndufv1, atpB, para, and ace, responsible for the expression of NADH dehydrogenase [ubiquinone] flavoprotein 1, ATP synthase, and acetylcholinesterase in insects, respectively. Lipidomic analyses exhibited a significant difference between two fumigants-exposed groups and the control, especially an ion with 815.46 m/z was analyzed less than twofold in the fumigants-treated group. It was identified as PI(15:1/18:3) and it may be used as a biomarker to EF and PH₃ toxicity. These findings may contribute to set an effective control strategy on T. urticae by methyl bromide alternatives such as EF and PH₃ because they have shared target sites on the respiratory chain in the pest.