Screening of larvicidal activities of eight plant essential oils against Thaumetopoea wilkinsoni Tams. (Lepidoptera: Thaumetopoeidae), a main pine defoliator in the Mediterranean

Thaumetopoea wilkinsoni Tams. is the most important pine defoliator in the Mediterranean Basin and can cause serious growth losses on trees. At this point, the purpose of this study was to investigate the larvicidal effects of eight plant essential oils as biological control agents for the pine processionary moth. For this purpose, Artemisia vulgaris L., Juniperus drupacea Labill., Melissa officinalis L., Ocimum basilicum L., Origanum majorana L., Rosmarinus officinalis L., Sideritis leptoclada O. Schwarz & P.H. Davis and Vitex agnus-castus L. essential oils were tested on the fourth/fifth larval periods of T. wilkinsoni. The essential oils from the eight plants were obtained by hydrodistillation and analysed by GC/MS. The most abundant compounds from each studied species were as follows: 1,8-cineole (20.68%) for R. officinalis, beta-pinene (26.73%) for S. leptoclada, linalool (38.67%) for O. majorana, p-mentha-1,5-dien-8-ol (36.44%) for M. officinalis, eugenol acetate (38.78%) for O. basilicum, 1,8-cineole (22.10%) for V. agnus-castus, d-limonene (45.21%) for J. drupacea and trans-beta-caryophyllene (21.22%) for A. vulgaris. The results show that all eight essential oils exhibited promising efficacy in a dose-dependent manner on T. wilkinsoni larvae after 24 hours. The highest larvicidal effect was obtained from J. drupacea, followed by O. basilicum, with LC50 values of 73.55 and 95.04 ppm, respectively. The data obtained from this study clearly indicate that J. drupacea and O. basilicum essential oils have the potential to have larvicidal effects and these findings point to the possibility of using the essential oil of the current species to control T. wilkinsoni.

Automated summary

This study investigated the larvicidal effects of eight plant essential oils on T. wilkinsoni larvae, and found that these oils exhibited promising efficacy in killing the larvae within 24 hours. The essential oils from J. drupacea and O. basilicum showed the highest larvicidal effects.