Chemical Composition and Insecticidal Potential of Pulicaria incisa (Lam) Essential Oil from Moroccan Plant Against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst.)

Abstract

Pulicaria incisa (Lam) is a wild-growing plant in Morocco and has been traditionally used by farmers to control pests of stored grains. The present study was conducted to investigate the chemical composition and insecticidal effect of the essential oil of P. incisa against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst.) by different methods (contact, fumigation and ingestion). The aerial parts of the plant were subjected to hydrodistillation using a Clevenger-type apparatus. The essential oil composition was analyzed by gas chromatography (GC) and mass spectrophotometry (MS). Sixty-six compounds representing 89.4% of total oil were identified. The main components were α-Ocimene (15.17%), τ-Cadinol (6.79%), α-Cadinol (4.51%), Alloaromadendrene (4.45%) δ-Cadinene, (+) - (4.13%). The repellant toxicity test results revealed a higher repellency effect in S. oryzae than T. castaneum. Lethal concentration (LC50), varied between 15.49 - 1.73 μL/cm2 and 20.89 - 2.29 μL/cm2 respectively. In the fumigation test, adults of S. oryzae and T. castaneum were sensitive to the essential oil with LC50 values varying between 16.21 - 2.08 and 18.62 - 2.51 μL/L air. In addition, experiments have shown that the ingestion method is the most toxic towards both insects with LC50 values of the order of 12.59 - 1.51 μL/g for S. oryzae and 14.12 - 2.39 μL/g for T. castaneum. While the lethal time (LT50) values decreased with increasing essential oil concentration, and in all cases, the increased susceptibility of both insects was directly associated with oil concentration and exposure time. This study aims to valorize medicinal and aromatic plants of the Moroccan flora in order to find novel bio-insecticidal products. Furthermore, the study reports for the first time the insecticidal activity of P. incisa against adults S. oryzae and T. castaneum.