Insecticidal toxicities of carvacrol and thymol derived from Thymus vulgaris Lin. against Pochazia shantungensis Chou & Lu., newly recorded pest

Abstract

The insecticidal toxicities of five essential oils against Pochazia shantungensis adults and nymphs, newly recorded pests, were evaluated. The LC50 values of Thymus vulgaris, Ruta graveolens, Citrus aurantium, Leptospermum petersonii and Achillea millefolium oils were recorded as 57.48, 84.44, 92.58, 113.26 and 125.78 mg/L, respectively, against P. shantungensis nymphs using the leaf dipping bioassay, and 75.80, 109.86, 113.26, 145.06 and 153.74 mg/L, respectively, against P. shantungensis adults using the spray bioassay method. Regarding volatile components identified in T. vulgaris oil, the LC50 values of carvacrol and thymol using the leaf dipping bioassay against P. shantungensis nymphs were 56.74 and 28.52 mg/L, respectively. The insecticidal action of T. vulgaris oil against P. shantungensis could be attributed to carvacrol and thymol. Based on the structure-toxicity relationship between thymol analogs and insecticidal toxicities against P. shantungensis nymphs similar to the LC50 values against P. shantungensis adults, the LC50 values of thymol, carvacrol, citral, 2-isopropylphenol, 3-isopropylphenol, and 4-isopropylphenol were 28.52, 56.74 and 89.12, 71.41, 82.49, and 111.28 mg/L, respectively. These results indicate that the insecticidal mode of action of thymol analogs may be largely attributed to the methyl functional group. Thymol analogues have promising potential as first-choice insecticides against P. shantungensis adults and nymphs.

Effects of plant extracts and essential oils on the behavior of Acrobasis advenella (Zinck.) caterpillars and females

“…For example, Tabari et al (2015) reported that carvacrol and thymol showed strong acaricidal activity against Dermanyssus gallinae (De Geer). Park et al (2017) demonstrated that thymol exhibited insecticidal activity against Pochazia shantungensis Chou & Lu adults and nymphs. In our experiment, by far the strongest repellent activity was shown by the tansy, but a low percentage of larvae were found on plants treated with extracts and oils from S. hortensis.…”

Traditional Uses, Chemical Constituents and Biological Activities of Plants from the Genus Thymus

“…Thymol, isolated from the ethanol extract of T. mongolicus , had strong acaricidal activities against Tetranychus viennensis . And thymol analogs have promising potential as first‐choice insecticides against Pochazia shantungensis adults and nymphs …”

“…[132] And thymol analogs have promising potential as firstchoice insecticides against Pochazia shantungensis adults and nymphs. [133]…”

GC-MS analysis and insecticidal effect of methanol extract of Pistacia khinjuk Stocks leaves

“…The main compounds of this plant were 5-ethoxy-4-phenyl-2-isopropylphenol (29.02 %), phenyl ethyl alcohol (phenethyl alcohol) (10.78 %), benzyl alcohol (7.8 %), 1,2-benzenesediol (6.67 %), spathulenol (2.07 %), and myrcene (2.03 %) ( Table 2). Existence of the isopropylphenol derivatives as thymol analogs and the main compound in MeOH extract of P. khinjuk leaves, are of pharmacological interest because they have insecticidal effect and so contribute to the plant's overall defense mechanism (Park et al, 2017). By using the spray bioassay against adults of Pochazia shantungensis Chou and Lu??…”