Ovicidal Activity of Essential Oils from Two Species of Ecalyptus on Two Spotted Spider Mite, Tetranychus urticae Koch
The two spotted spider mite Tetranychus urticae Koch is one of the polyphagous pests of crops worldwide. Due to undesirable effects of synthetic pesticides such as expression of resistance in mites, this research was conducted to achieve alternative safe compounds to environment. Therefore, ovicidal activity of essential oils of Eucalyptus salmonophloia F. Muell and Eucalyptus kingsmillii Maiden (Mauden) blakely was studied on two-spotted spider mites at 27 ± 0.5°C, 50 ± 5% RH and photoperiod 16: 8 h (L: D). The essential oils were extracted by Clevenger type apparatus. Concentrations of 3.75, 8.28, 11.57, 15.60 and 19.32 µL/L air were put on filter papers with 2 cm diameter and kept in the cap of bottle. The eggs were fumigated for one and three days and then, they were transferred to new clean dishes. The hatched eggs were counted 24 h after fumigation. LC50 values of E. Salmonophloia and E. Kingsmillii were 14.39 and 14.14 µL/L air on one-day old eggs and 7.17 and 7.19 µL/L air on three-day old eggs, respectively. Based on LC50 values, ovicidal activity of these two essential oils was not significantly different; however, 72 h fumigation was significantly more effective than 24 h fumigation. The chemical composition of the essential oil was assessed by GC and GC-MS. 1,8-Cineol, P-cymene and α-Pinene were determined to be the major constituents of the oils.