Abstract: Mineral oils with high quality are seeing more recognition in modern pest management approaches and internationally accepted for use in organic farming as pesticides. Mineral oils are mixtures including a lot of components，and their components and proportion determined physical and chemical properties and pest control effect. The equivalent Normal-paraffin carbon numbers (nCy) and carbon number distribution of four mineral oils (SK EnSpray99, Caltex Lovis Miscible Summer Oil, Ampol D-C-Tron Spray oil, and Citrole paraffin oil)  (hereinafter referred to as SK, Caltex, Ampol and Citrole oil, respectively) and six molecular distillation fractions (＜120℃, ＞120℃, ＜105℃, 105－120℃ fractions of Caltex oil, and ＜110℃ and ＞110℃ fractions of SK oil)  were determined and the oviposition repellent effects of their 0.5% aqueous emulsions against the oriental fruit fly, Bactrocera dorsalis, were bioassayed by dipping treatment in the laboratory. The results showed that the average puncture numbers of B. dorsalis on banana treated with SK, Caltex, Ampol, Citrole oil and water were 17.850±1.282, 3.400±0.630, 15.850±1.439, 20.650±1.212, 19.050±1.155, respectively, and those on starfruit were 15.500±3.969, 3.000±0.707, 13.750±4.131, 17.250±4.385, 62.000±4.708, respectively, and those on banana treated with 6 molecular distillation fractions were 4.400±1.166, 8.200±0.583, 5.400±1.720, 2.400±1.077, 4.800±1.594, 12.200±2.63, respectively. There was significant difference in oviposition repellency against B. dorsalis among mineral oils (P<0.05), and nCy of mineral oils with the best repellent effect was nC23 or so. Correlation analysis of Spearman’s rank correlation coefficient (Spearman’s rho) test between carbon number distribution and oviposition repellency of mineral oils showed that there was a significant positive correlation between the repellent effect and the content of C23 of mineral oils (P<0.05). The results would be helpful to further research the repellent components of mineral oils against pests and the repellent mechanism.

Key words: Mineral oil, Bactrocera dorsalis, oviposition repellency, effective component, molecular distillation