Behavioural responses of the parasitoid Aphytis melinus to volatiles organic compounds (VOCs) from Aonidiella aurantii on its host fruit Tahitian lime fruit Citrus latifolia

Abstract

Aphytis melinus DeBach (Hymenoptera: Aphelinidae) is a parasitoid of Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae). However, the cues used by A. melinus for host location have not been extensively investigated. Many studies have shown that mating parasitoids are strongly attracted by specific volatiles from infested plants. This paper investigated the response of A. melinus to volatiles from Tahitian lime fruit infested with A. aurantii through two-choice olfactometer bioassays. First, we identified the chemicals emitting from non-infested and A. aurantii-infested lime fruit via gas chromatography-mass spectrometry analyses and solid phase microextraction and identified 26 volatile organic compounds (VOCs). Eighteen of these were increased by A. aurantii infestation, and one was decreased, whereas five compounds were produced exclusively from infested fruit. Innate positive chemotaxis of mating A. melinus females toward lime fruit and their VOCs was then tested in olfactometer assays. Compared to the control without fruit, female A. melinus showed significantly greater attraction to healthy and A. aurantii-infested lime fruit, while there were no significant differences in the attraction of the parasitoid between healthy fruit or fruit infested with the second and third instar of A. aurantii. Among the two synthetic compounds tested, d-limonene and β-ocimene elicited a strong attraction for parasitoids at tested dosages (15 μl/ml), indicating an intrinsic response to this compound as a short-range attractant. Results from this study suggest that A. melinus parasitoids mainly rely on olfactory cues in host habitat location and that d-limonene and β-ocimene are the major attractants in infested fruit volatiles. Practically, field applications of this volatile may play a significant role in attracting more A. melinus to enhance the efficiency of biological control of A. aurantii in the future.