Effects of Growth Phase and Ultraviolet-B Pretreatment in Perilla Leaves on the Two-Spotted Spider Mite

Evaluation of acaricidal effect of terpinolene and γ-terpinene on Hyalomma anatolicum and in silico screening of herbs

IMPORTANCE

Terpenoids of a plant origin are a class of alternatives to chemical acaricides for tick control. Despite this, few studies have evaluated the efficacy of terpenoid-containing herbal extracts or individual terpenoids in Hyalomma anatolicum.

OBJECTIVE

This study evaluated the killing efficacy of terpinolene and γ-terpinene against H. anatolicum to identify herbs rich in these compounds as potential candidates for future materials in the control of H. anatolicum.

METHODS

Terpinolene and γ-terpinene were subjected to adult tick immersion experiments to evaluate their killing effect on H. anatolicum, following their identification post-collection. The herbs were screened for the two terpenoids using the HERB database, and the resulting data were categorized and analyzed.

RESULTS

The acaricidal effect of terpinolene and γ-terpinene against H. anatolicum showed a clear dose-response relationship, with effective doses LC₅₀ of 6.60 mg/mL and 4.86 mg/mL, respectively. In silico analysis revealed the presence of terpinolene and γ-terpinene in 52 and 36 herbs, respectively, with 16 herbs containing both compounds. These herbs could be grouped into 35 plant families. In particular, Lamiaceae and Apiaceae emerged as the most represented families, each accounting for 9.23% of the total herbs identified, followed by Zingiberaceae (7.69%) and Asteraceae and Rutaceae (6.15% each).

CONCLUSIONS AND RELEVANCE

Terpinolene and γ-terpinolene have good killing effects against H. anatolicum. Herbs rich in the two terpenoids are promising candidates as plant-derived materials for managing H. anatolicum.

Effects of Nocturnal UV-B Irradiation on Growth, Flowering, and Phytochemical Concentration in Leaves of Greenhouse-Grown Red Perilla

In Japan, red perilla leaves are used in the food and coloring industries, as well as in crude medicine. Perilla leaves contain a high concentration of phytochemicals such as perillaldehyde (PA) and rosmarinic acid (RA). The effects of UV-B radiation intensity (0.05–0.2 W m⁻², UV-B_BE: 0.041–0.083 W m⁻²), duration (3 or 6 h), and irradiation method (continuous or intermittent) for artificial nocturnal lighting using UV-B fluorescent lamps were evaluated on growth, flowering, and leaf phytochemical concentration in greenhouse-grown perilla. Under continuous UV-B irradiation at 0.1 W m⁻² for 3 or 6 h, leaf color changed from red to green and leaf fresh weight decreased, compared with the control treatment. No leaf color change was observed under the 3-h treatment with UV-B radiation at 0.05 W m⁻², wherein leaf fresh weight was similar to that of the control. Furthermore, RA concentration under continuous UV-B irradiation at 0.05 W m⁻² for 3 h increased two-fold compared to that under control treatment, while PA concentration was not affected by UV-B irradiation. Thus, our data showed that continuous UV-B irradiation at 0.05 W m⁻² for 3 h could effectively produce RA-rich perilla leaves without reducing in phenotypic quality or productivity. However, a 6-h intermittent illumination inhibited flowering without altering phytochemical concentration.