矿物油乳剂作用下橘小实蝇的产卵拒避及触角电位反应

为了研究矿物油乳剂对害虫行为的干扰作用，测定和比较了4种矿物油乳剂对橘小实蝇Bactrocera dorsalis (Hendel)的产卵拒避效果及在其作用下该虫的触角电位反应（EAG），并测试了其中拒避效果最好的Caltex Lovis夏用油的不同施用方式（浸蘸法和喷雾法）及不同施用浓度（150，250，350，450倍液）对橘小实蝇产卵拒避的影响。结果显示：分别用4种矿物油乳剂200倍液以浸蘸法处理香蕉，仅Caltex Lovis夏用油处理对橘小实蝇产卵拒避效果显著，其平均产卵孔数仅为清水对照的15.14%；其他3种矿物油乳剂则没有明显效果。这表明矿物油乳剂对昆虫行为的干扰作用与其组成成分相关。4种矿物油乳剂对橘小实蝇的产卵拒避效果与各矿物油乳剂的50倍液滴于滤纸条后0.5 h的雌成虫EAG值间无显著相关性，但与滴于滤纸条后3 h（滤纸条上水分已蒸发）的EAG值间有显著的负相关性，说明矿物油乳剂的挥发性组分对橘小实蝇的产卵拒避影响不大，因此推测矿物油乳剂在植物表面形成的油膜对植物挥发性物质的封闭作用与其产卵拒避效果可能有一定的关系。浸蘸法不同浓度处理间的产卵拒避效果无显著差异，均明显高于喷雾法处理及清水对照。在喷雾法处理中，仅150倍液有显著产卵拒避效果。这说明，矿物油乳剂需要在植物表面达到一定的沉积量，才能对橘小实蝇有较好的产卵拒避作用。与喷雾法相比，浸蘸法可能较利于矿物油在植物表面的沉积，这也佐证了矿物油乳剂所形成油膜的封闭性与其产卵拒避效果有一定的关系。

Oviposition repellency and EAG responses of the Oriental fruit fly,Bactrocera dorsalis(Hendel)to mineral spray oils

In order to determine the impact of mineral oils on insect behavior, oviposition behavioural responses of the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) females to deposits of 0.5% (v/v) aqueous emulsions of each of the four HMOs were determined for banana fruit that were dipped in the emulsions. The oils were nC21.5 Total Citrole, nC21 Caltex Lovis, nC23 Ampol D-C-Tron NR and nC24 SK EnSpray 99. Oviposition in fruit dipped in Lovis was significantly lower (85%) than in water-dipped fruit. The other three oils had no impact on oviposition. The results suggested that the influence of mineral oils on the females could be related to the composition of oils. Electroantennogram (EAG) responses of females to volatiles emanating from pieces of filter paper onto which drops of 2% (v/v) emulsions were placed were also determined for each oil. There was no significant correlation between the oviposition repellency of the four HMOs against fruit fly and the EAG responses of female fruit flies to 0.5 hour deposits from which water in the emulsions had not evaporated. However, there was a significant negative correlation between the oviposition repellency and the EAGs responses for 3 hour deposits on filter papers from which all water had evaporated. This suggested that oil volatiles had little effect on repelling female B. dorsalis fruit fly. It was hypothesised that oil deposits may block the release of plant volatiles that female B. dorsalis are attracted to in order to lay their eggs. Ovipositional responses to bananas sprayed or dipped with 0.0% (water), 0.22%, 0.29%, 0.4% and 0.67% (v/v) of Lovis oil were compared in a subsequent experiment. Oviposition in dipped fruit was significantly lower than in the sprayed fruit and the water controls. But there was no difference among the oil-dipped treatments, and in the sprayed treatments, only the 0.67% oil treatment was significantly different from the water sprayed control. These results indicates that for deposits to be effective they must exceed deposits equivalent to or greater than those achieved with the 0.22% dip and 0.67% spray used in the experiments. It was evident that dipping was more efficient than spraying to deposit mineral oils on plant surface, and this further proved that oil film forming on surface of fruits which blocked plant volatiles was related to oviposition repellency against the fruit fly.