Abstract
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.
Highlights
Two spotted spider mites, Tetranychus urticae, is a polyphagous herbivore and quickly abundant in host plant fields because of short life span and some favorable growth conditions
LC99 values were very similar up to about 10 mg/L, but LC50 values showed that nymphs were susceptible about 2.5 times lower in ethyl formate (EF) treatment in comparison to eggs and adults
EF and P H3 are the representative fumigants replaced to methyl bromide in South Korea
Summary
Tetranychus urticae, is a polyphagous herbivore and quickly abundant in host plant fields because of short life span and some favorable growth conditions. They are one of major crop pests, which are caused loss of crop production and quality [1]. A variety of control methods including natural acaricides are developed to reduce T. urticae attack on cultivated vegetables. For the control of two-spotted mites, T. urticae, a variety of disinfection methods have introduced in the agricultural market. Chemical control of T. urticae has been used worldwide and a variety of acaricides are introduced in the agricultural market [6]
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