Repellent, oviposition-deterrent and egg-hatching inhibitory effects of some plant essential oils against citrus mealybug, Planococcus citri Risso (Hemiptera: Pseudococcidae)

The citrus mealybug (Planococcus citri) is a serious pest of citrus groves in Turkey and has recently caused considerable damages to some cut flowers (especially, roses and orchids) in greenhouses in Antalya (southwestern Turkey). In this study, repellent and oviposition-deterrent activities of essential oils from anise (Pimpinella anisum), rosemary (Rosmarinus officinalis), peppermint (Mentha piperita), Turkish oregano (Origanum onites) and thyme (Thymus vulgaris) were investigated against female adults of P. citri under laboratory conditions. The results from the study showed that all the essential oils tested had a repellent activity in varying degrees, and the repellency was concentration and time dependent. Based on the highest dose (5 mL/L water) and the longest time period after the insect introduction (96 h), the oils from O. onites and T. vulgaris had the highest percent repellency in both choice and no-choice tests (O. onites: 88.9 and 65.4%; T. vulgaris: 88.8 and 69.6%, respectively), and followed by P. anisum (80.1 and 50%) and R. officinalis (57.1 and 45.2%) oils. In the oviposition deterrency assays using the highest concentration (5 mL/L water), O. onites essential oil showed the most potent oviposition deterrency (63.7%) resulting in the lowest mean number of eggs laid by the mealybug females (48.8 eggs per female) followed by P. anisum (56.9%). Furthermore, these two oils had the most potent egg-hatching inhibitory effects and inhibited egg hatching by 59.2 and 46.8%, respectively. Overall results suggest that the essential oils tested may help for us in controlling P. citri populations in various agroecosystems.