Seasonal variation and bioactivity of the essential oils of two Juniperus species against Aedes (Stegomyia) albopictus (Skuse, 1894).

The seasonal variation in respect to the yield and chemical composition of 24 essential oils (EOs) isolated from various parts (leaves and fruits) of two indigenous Greece Juniperus species (family Cupressaceae), namely Juniperus drupacea and Juniperus phoenica, were determined by GC and GC/MS analysis. The larvicidal properties of these EOs were evaluated against 3rd and early 4th instar larvae of Aedes (Stegomyia) albopictus (Skuse, 1894) at one screening dose (29 mg L(-1)). Moreover, the repellent activity against adult mosquitoes was also evaluated at one screening dose. The analytical data indicated that the EOs mainly consisted of monoterpenes, mostly cyclic and only occasionally aliphatic and to a lesser percent diterpenes. The EOs yield was sharply increased when the plant material was subjected to pre-treatment before steam distillation. Finally, the influence of plant material collection period on their yield and chemical content was also determined. Bioactivity assessments indicated that three EOs possess very potent larvicidal properties and 12 EOs display significant repellent activities since they were proved to be "DEET-like." Therefore, they represent an inexpensive source of natural mixtures of larvicidal and repellent mixture of natural compounds, with potentials for application for utilization in mosquito control schemes in order to prevent the expansion of viral infections.