Antifungal and Insecticidal Activity of two Juniperus Essential Oils

Abstract

Essential oils of two Tibetan Junipers Juniperus saltuaria and J. squamata var. fargesii (Cupressaceae) were obtained by distilling dried leaves and branches using a Clevenger apparatus. Sixty-seven compounds from J. saltuaria and 58 from J. squamata var. fargesii were identified by gas chromatography—mass spectrometry (GC-MS). Both essential oils contained similar ratios of four abundant monoterpenoids: 44 and 35% sabinene, 13 and 9% elemol, 8 and 7% terpinen-4-ol, and 4 and 17% α-pinene, respectively. These oils had antifungal activity based on a direct bioautography assay of Colletotrichum acutatum, C. fragariae, and C. gloeosporioides, and insecticidal activity based on serial-time mortality bioassay of azalea lace bugs, Stephanitis pyrioides. Antifungal activity of Juniperus oils was weak when compared with commercial fungicides such as benomyl and captan. Whole Juniperus oils at quarter the dosage used against Colletotrichum species were more insecticidal than 10 mg/mL malathion, killing ≥70 - 90% adult lace bugs after 4 hours of exposure. Rf values of 0.18 for J. saltuaria oil and 0.19 for J. squamata oil indicated lipophilic monoterpenes which were the putative sources of biological activity.