Thirty-four plant essential oils were screened for their acaricidal and oviposition deterrent activities against two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae), in the laboratory using a leaf-dip bioassay. From initial trials, sandalwood and common thyme oils were observed to be the most effective against TSSM adult females. Subsequent trials confirmed that only sandalwood oil was significantly active (87.2 ± 2.9% mortality) against TSSM adult females. Sandalwood oil also demonstrated oviposition deterring effects based on a 89.3% reduction of the total number of eggs on leaf disks treated with the oil. GC–MS analysis revealed that the main components of the sandalwood oil were α-santalol (45.8%), β-santalol (20.6%), β-sinensal (9.4%), and epi-β-santalol (3.3%). A mixture of α- and β-santalol (51.0:22.9, respectively) produced significantly higher mortality (85.5 ± 2.9%) and oviposition deterrent effects (94.7% reduction in the number of eggs) than the control. Phytotoxicity was not shown on rose shoots to which a 0.1% solution of sandalwood oil was applied.

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Morphology of antennal sensilla and their distributions were investigated in male and female adults of two tortricid moths, Cydia pomonella and C. succedana using scanning electron microscopy. The antennae of both sexes of the two species were filiform, and the overall lengths of the antennae and the number of consisting segments were greater in males than in females. Six types of sensilla (s.) were identified from the antennae of both sexes in the two species: s. trichodea, s. basiconica, s. coeloconica, s. auricillica, s. chaetica, and s. styloconica, in varying numbers and distribution along the antennae. Among them, surface of four sensilla types (s. trichodea, s. basiconica, s. coeloconica, s. auricillica) were multiporous in the two species, indicating that the primary function of these sensilla is olfactory. The s. trichodea were the most numerous on the antennae in both sexes of the two species. Male C. pomonella has a greater number of s. trichodea than the female. The four sensilla types were further divided into different subtypes in the two species; s. trichodea into three subtypes, s. basiconica into two subtypes, s. coeloconica into two subtypes in C. pomonella and one subtype in C. succedana, and s. auricillica into two subtypes. Sexual dimorphism was observed in the subtypes of s. trichodea. The long subtype of s. trichodea occurs only on male antennae, whereas the short subtypes mainly on female antennae. These findings would be helpful for further studies on detailed chemo-receptive functions of each subtype of the antennal sensilla.

The bean bug, Riptortus pedestris is a major pest of bean pods and some tree fruits in north-east Asian countries. Scanning electron microscopy was conducted to investigate the morphology and distribution of antennal sensilla of R. pedestris to help in understanding the sensory mechanisms of the bug. Average antennal lengths of male and female R. pedestris were 11.00 mm and 9.84 mm, respectively, consisting of four distinct segments, scape, pedicel, basiflagellum, and distiflagellum. Based on the gross appearance, the antennal sensilla were classified into four major types (trichodea, basiconica, chaetica, and coeloconica), which could be further classified into four trichoid, three basiconic, four chaotic, and two coeloconic subtypes, based on their size, tip shape, presence of socket, and surface structure. Among them, two subtypes of trichoid sensilla, all three subtypes of basiconic sensilla, four subtypes of chaetic sensilla and two subtypes of coeloconic sensilla had numerous pores along the surface, suggesting their olfactory function. Nine subtypes (2 trichoid, 1 basiconic, 4 chaetic, and 2 coeloconic subtypes) showed a distinct socket structure at the base. Among the four antennal segments, the distiflagellum possessed highest number of sensilla. Trichoid sensilla were most abundant, followed by basiconic, chaetic, and coeloconic sensilla. Each subtype of sensilla exhibited distinct distribution profile along the four antennal segments. Two subtypes of trichoid sensilla, one subtype of basiconic sensilla and one subtype of chaetica sensilla were distributed on scape, pedicel, and basiflagellum, whereas distribution of other subtypes of sensilla was confined to basiflagellum and distiflagellum. Microsc. Res. Tech. 79:501-511, 2016. © 2016 Wiley Periodicals, Inc.

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