Behavioral and Electrophysiological Effects of Ajowan (Trachyspermum ammi Sprague) (Apiales: Apiaceae) Essential Oil and Its Constituents on Nymphal and Adult Bean Bugs, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae).

We investigated the repellent effect of 12 Apiaceae plant essential oils on nymphal and adult (male and female) forms of the bean bug, Riptortus clavatus (Thunberg) (Hemiptera: Alydidae), using a four-arm olfactometer. Among the essential oils tested, ajowan (Trachyspermum ammi Sprague) essential oil showed the strongest repellent activity against the nymphal and adult bean bugs. For female adults, the repellent activity was significantly different between an ajowan oil-treated chamber and an untreated chamber down to a concentration of 14.15 µg/cm2. We also investigated the repellent activity of individual ajowan essential oil constituents. Of the compounds examined, carvacrol and thymol showed the most potent repellent activity against the nymphal and adult bean bugs. Carvacrol and thymol exhibited 73.08% and 70.0% repellent activity for the bean bug nymph at 0.71 and 2.83 µg/cm2, respectively, and 82.6% and 80.7% at 5.66 and 11.32 µg/cm2, respectively, for male adults. Carvacrol and thymol exhibited strong repellent activity against female adult bean bugs down to a concentration of 2.83 µg/cm2. Ajowan essential oil, thymol and carvacrol elicited a negative electroantennogram (EAG) response from adult bean bugs. This could explain the repellent activity of ajowan essential oil and its constituents. Our results indicate that ajowan essential oil and its constituents carvacrol and thymol can be potential candidates as the 'push' component in a 'push-pull' strategy for bean bug control.

Fumigant Antifungal Activity via Reactive Oxygen Species of Thymus vulgaris and Satureja hortensis Essential Oils and Constituents against Raffaelea quercus-mongolicae and Rhizoctonia solani.

In this study, the fumigant antifungal activity of 10 Lamiaceae plant essential oils was evaluated against two phytopathogenic fungi, Raffaelea quercus-mongolicae, and Rhizoctonia solani. Among the tested essential oils, thyme white (Thymus vulgaris) and summer savory (Satureja hortensis) essential oils exhibited the strongest fumigant antifungal activity against the phytopathogenic fungi. We analyzed the chemical composition of two active essential oils and tested the fumigant antifungal activities of the identified compounds. Among the tested compounds, thymol and carvacrol had potent fumigant antifungal activity. We observed reactive oxygen species (ROS) generation in two fungi treated with thymol and carvacrol. Confocal laser scanning microscopy images of fungi stained with propidium iodide showed that thymol and carvacrol disrupted fungal cell membranes. Our results indicated that ROS generated by thymol and carvacrol damaged the cell membrane of R. querqus-mongolicae and R. solani, causing cell death.

Effects of Pheromone Dose and Trap Height on Capture of a Bast Scale of Pine, Matsucoccus thunbergianae (Hemiptera: Margarodidae) and Development of a New Synthesis Method.

Matsuone is a well-known sex pheromone of the genus Matsucoccus (Hemiptera: Margarodidae), including species Matsucoccus matsumurae (Kuwana), Matsucoccus resinosae Bean & Goldwin, and Matsucoccus thunbergianae Miller & Park. In this study, we investigated the effects of matsuone dose and trap height on the capture of M. thunbergianae and developed an alternative synthesis of racemic matsuone. In field trapping experiments, M. thunbergianae males showed dose-dependent attraction to (6R,10R/S)-matsuone from 100 µg up to an approximate saturation level of 1,600 µg per rubber septum lure. Traps baited with (6R,10R/S)-matsuone and installed 50 cm above ground level attracted more males than traps 100 and 150 cm above ground level. To reduce synthesis procedures, time, and labor, we developed a new synthetic route to racemic matsuone and conducted field experiments with the product. Although traps baited with the racemic matsuone were less attractive than traps baited with (6R,10R/S)-matsuone synthesized by a previously reported method, the new synthetic route could be an economically favorable alternative to the previous method used in production of lures for field application.

Identification of Aggregation-Sex Pheromone of the Korean Monochamus alternatus (Coleoptera: Cerambycidae) Population, the Main Vector of Pine Wood Nematode.

We confirmed an aggregation-sex pheromone of the Korean Monochamus alternatus Hope (Coleoptera: Cerambycidae) population, which primarily transmitted the pine wood nematode in Korea. Only the M. alternatus male emitted monochamol which has been previously reported in the Chinese M. alternatus population. In field attraction testing, the monochamol+α-pinene+ethanol combination attracted more M. alternatus adult beetles than traps containing only monochamol, ethanol, or α-pinene. The bark beetle aggregation pheromone compounds of ipsenol, ipsdienol, and ipsenol+ipsdienol, did not show synergistic effects with the monochamol+α-pinene+ethanol combination. No synergistic effects were observed when each host volatile compound of 3-carene, ß-caryophyllene, limonene, myrcene, and ß-pinene was added to traps containing monochamol+α-pinene+ethanol. The ratio of female beetles was much higher in traps containing the monochamol+α-pinene+ethanol combination than that of the natural population. Our results indicated that pheromone and synergists could be useful for managing the M. alternatus population.