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D-limonene and β-ocimene Attract Aphytis melinus to Increase Parasitism of California Red Scale Aonidiella aurantii (Hemip-tera: Aphididae) on Citrus
* 1 , 2 , 2
1  Mosul University
2  Murdoch University
Academic Editor: Junwei (Jerry) Zhu


Under field conditions, the natural enemies’ effectiveness in controlling pests is largely corre-lated with their capability to spread towards infested crops. We previously reported that Aphytis melinus (Hymenoptera: Aphelinidae), a parasitoid of California red scale Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae), was attracted to volatiles from citrus fruit infested with A. aurantii and that d-limonene and β-ocimene A. aurantii -induced plant volatiles were responsible for this attraction. In this study, d-limonene and β-ocimene were examined for their attractive-ness to A. aurantii parasitoid Aphytis melinus in the field after augmentative releases. Both were mixed with paraffin oil for slow release in field experiments to control the population density of A. aurantii by enhancing their natural enemies. The experiment was conducted in 2018 at Mur-doch citrus orchard. A total of 10,000 A. melinus adults were released in different spots of the cit-rus orchard. The spread of the parasitoid was evaluated, for three months after the release, using yellow sticky traps activated with both of d-limonene and β-ocimene and by monitoring the percentage parasitism of the scale on citrus fruit. Field experiments demonstrated that lures baited with isolates of d-limonene and/or β-ocimene, which significantly attracted some species of natural enemies but had no significant impact on other recruitments. The number of A. meli-nus captured during the whole trial was greater in the traps treated with volatiles than the con-trol. Finally, we determined that overall parasitism rates were not increased by synthetic HIPV lures but found evidence that lures may increase parasitism of A. aurantii when there is a de-crease in the amount of volatile organic compounds due to lack of healthy and infested fruit.

Keywords: d-limonene; β-ocimene; California red scale; Aphytis melinus; herbivore-induced plant volatile; conservation biological control