Sex‐specific responses of Asian citrus psyllid to volatiles of conspecific and host‐plant origin

Abstract

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the primary vector of Candidatus Liberibacter spp. bacteria that cause citrus greening, a disease of worldwide importance. Olfactometry was employed to test responses of D. citri to odours from intact citrus plants (Mexican lime, Citrus aurantifolia, sour orange, Citrus aurantium, Marsh grapefruit, Citrus paradisi and Valencia orange, Citrus sinensis), citrus plants previously infested with D. citri, and odours of conspecifics including nymphs, adult insects of same and opposite sex, and their products (honeydew), both alone and in combination. In contrast to other studies, psyllids of both sexes were attracted to volatiles of undamaged Mexican lime leaves, whereas undamaged grapefruit attracted only females, and leaves of Valencia and sour orange did not attract either sex. All four plant species attracted female psyllids when previously infested, but only Mexican lime and sour orange-attracted males. Thus, Citrus species appear to vary in the production of both constituitive and induced volatiles that attract adult psyllids. Volatiles emitted by nymphs did not attract either sex, but psyllid honeydew was attractive to males, likely due to female pheromone residues. Males oriented to the odour of females, whereas the reverse was not true, and neither males nor females oriented to samesex volatiles. The addition of conspecific cues (adults, nymphs or honeydew) did not increase female attraction to previously infested leaves, but male response was increased by the presence of adults and honeydew, regardless of plant species. Thus, female psyllids appear to orient more strongly to volatiles of plant origin, whereas males respond more strongly to cues emanating from females and conspecific excretions. These results suggest that female psyllids drive the initial colonization of host plants, whereas males orient to females and infested plants. Identification of the specific volatiles involved may permit their use in monitoring and management of this pest.

Male Psyllids Differentially Learn in the Context of Copulation

“…Once in close proximity, female-produced cuticular hydrocarbons, which appear to function as sex pheromones, attract males to engage in courtship and copulation [12,18,19]. It is likely that these pheromones function as short-distance cues used after vibrational communication has allowed long-distance detection along the plant surface.…”

Innate and Conditioned Responses to Chemosensory and Visual Cues in Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae), Vector of Huanglongbing Pathogens

“…Wenninger et al [ 14 ] found that D. citri responded to visual stimuli in the absence of host-plant odor, suggesting that visual cues alone are sufficient to elicit attraction to host-plants. Nonetheless, D. citri is stimulated by host-plant odors [ 14 , 15 , 16 , 17 , 18 ] and olfaction seems to play some role in host-plant selection. The nature of that role, however, is not clear; i.e.…”

Population genetic structure of Diaphorina citri Kuwayama (Hemiptera: Liviidae): host-driven genetic differentiation in China

“…Field observations showed that Citrus medical suffered the heaviest from D. citri , followed by Citrus sinensis , with Citrus reticulate the lightest 78 , 79 . Female D. citri orient to their plant of origin; males orient to the odor of females and co-specific excretions 80 . This behavior in combination with female oviposition preference behavior likely results in mate choice and limits gene flow between D. citri from different host plant clusters 81 , 82 .…”