Symbionticidal And Fungicidal Activities Of Certain Essential Oils

• Ahlam A. M. Alfazairy
• Department of Entomology, Faculty of Agriculture, University of Alexandria, Alexandria, Egypt

Abstract

The hydrodistillated essential oils from leaves of both the Egyptian cypress Cupressus sempervirens L. and the lemon-scented gum Eucalyptus citriodora Hook, and seeds of the baldcypress Taxodium distichum L. were tested for their symbionticidal and fungicidal effects. When the kalotermitid Kalotermes flavicollis Fabr. pseudergates exposed to Casuarina-wood wafers treated separately with different concentrations (5, 15, and 30 ?l/2g wood wafer) of the subject essential oils, their spirochaete and flagellate populations abnormally were reduced in numbers and vigour. The adverse effect of the tested essential oils on K. flavicollis symbiotic microbiota in the hindgut paunch of moribund pseudergates seemed, in general, to be oil variety-, posttreatment period-, and dose-dependent. Of the four symbiotic flagellates found in K. flavicollis pseudergates, the lophomonadids Joenia sp. and Mesojoenia sp. were the most adversely affected flagellates followed by the polymastigid Foaina sp. and the trichomonadid Tricercomitus sp. On the other hand, of the three essential oils, the T. distichum essential oil evidently appeared to have the greatest adverse effect on test flagellates (95-100% decline in numbers within 2 to 4 days) followed by the E. citriodora (89-100%) and the C. sempervirens oils (31-100%). While with the hindgut spirochaetes, the adverse effect seemed to be reversed where the E. citriodora essential oil had the greatest effect (54-100%) followed by C. sempervirens (46-100%) and T.distichum (8-100%) oils. Also, the subject essential oils were assayed for their antifungal activity, at 5, 10, 15, 20, 25, 30, 40, 50 and 60 ?l/1ml acetone/15ml Czapek-Dox medium against isolates of four woodrotting fungi associated with Casuarina timber, Aspergillus sp. Penicillium sp., Fusarium sp. and Mucor sp., by a method based on inhibition of the fungus growth on agar plates. Growth inhibited by the three test essential oils in a dose-dependent manner. Of the three essential oils, E. citriodora exhibited the most potent fungicidal activity against the tested four fungi, followed by T. distichum oil. While the C. sempervirens essential oil appeared to have the least significant antifungal property.