Diaphorina citri Kuwayama (Hemiptera: Psyllidae) carries Candidatus liberibacter spp., the putative causal agents of Huanglongbing. D. citri reproduces and develops only on the flushing shoots of its rutaceous host plants. Here we examined whether D. citri is attracted to host plant odors and a mixture of synthetic terpenes. Tests conducted in a vertically oriented Y-tube olfactometer showed that both males and females preferentially entered the Y-tube arm containing the odor from the young shoots of Murraya paniculata (L.) Jack and Citrus limon L. Burm. f. cultivar Eureka. Only males exhibited a preference for the odor of C. sinensis L., whereas the odor of C. × paradisi MacFadyen cultivar Rio Red was not attractive to both sexes. The volatiles emitted by young shoots of grapefruit cultivar Rio Red, Meyer lemon (Citrus × limon L. Burm.f.), and M. paniculata were analyzed by gas chromatograph-mass spectrometry. The samples were comprised of monoterpenes, monoterpene esters, and sesquiterpenes. The number of compounds present varied from 2 to 17, whereas the total amount of sample collected over 6 h ranged from 5.6 to 119.8 ng. The quantitatively dominant constituents were (E)-β-ocimene, linalool, linalyl acetate, and β-caryophyllene. The attractiveness of a mixture of synthetic terpenes, modeled on the volatiles collected from M. paniculata, was evaluated in screened cages in a no-choice test. At three observation intervals, significantly more individuals were trapped on white targets scented with the mixture than on unscented targets. These results indicate the feasibility of developing D. citri attractants patterned on actual host plant volatiles.

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Responses of the Asian Citrus Psyllid to Volatiles Emitted by the Flushing Shoots of Its Rutaceous Host Plants

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important worldwide pest of citrus that vectors bacteria (Candidatus Liberibacter spp.) responsible for huanglongbing (citrus greening disease). We examined the behavioral responses of mated and unmated D. citri of both sexes to odors from host plants in a Y-tube olfactometer, with and without visual cues. The host plants tested were 'Duncan' grapefruit (Citrus paradisi Macfayden), sour orange (Citrus aurantium L.), navel orange (C. sinensis L.), and Murraya paniculata L. Jack. Responses varied by plant species, psyllid sex and mating status, and the presence of a visual cue. Evidence of attraction generally was stronger in females and in mated individuals of both sexes relative to virgins. The presence of a visual cue typically enhanced attractiveness of olfactory cues; in no case did unmated individuals show evidence of attraction to host plant odors in the absence of avisual cue. In the absence of visual cues, mated females and males showed evidence of attraction only to odors from sour orange and navel orange, respectively. Psyllids exhibited anemotactic responses when assayed with plant odors alone but showed strong evidence of attraction only when olfactory and visual cues were combined, suggesting that olfactory cues facilitate orientation to host plants but may be insufficient alone. Antennal responses to citrus volatiles were confirmed by electroantennogram. The results reported here provide evidence that D. citri uses olfactory and visual cues in orientation to host plants and suggest the possibility of using plant volatiles in monitoring and management of this pest.

https://bioone.org/journals/Environmental-Entomology/volume-38/issue-1/022.038.0128/Roles-of-Olfactory-Cues-Visual-Cues-and-Mating-Status-in/10.1603/022.038.0128.pdf

Roles of olfactory cues, visual cues, and mating status in orientation of Diaphorina citri Kuwayama (Hemiptera: Psyllidae) to four different host plants.

Evolutionary and biological patterns can be obscured by inadequate or ill-defined terminology. An example is the generally very specific relationship between the sap-feeding hemipteran group, psyllids, and their breeding plants, commonly called host-plants. The literature is clogged with references to so called ‘hosts’, which are often merely plants on which psyllids were found accidentally, and no immature development was detected. Recently the term host has also been applied by some authors to any plant on which immature or adults feed. Here we propose a terminology to clarify associated plant definitions, and we suggest restricting the use of the term host-plant to plants on which a psyllid species completes its immature to adult life cycle. For the other plant associations we suggest the terms overwintering or shelter plant (plants on which adult psyllids overwinter and on which they may feed), food plant (plants on which adult psyllids feed, but do not breed and do not spend an extended period of time) and casual plant (plants on which adult psyllids land but do not feed).

/pdf/psyllid-host-plants-hemiptera-psylloidea-resolving-a-5vgnmgbavt.pdf

Psyllid host-plants (hemiptera: psylloidea): resolving a semantic problem

Many phytopathogens that cause worldwide losses of agricultural yield are vectored by herbivorous insects. Limited information is available about the interactions among phytopathogens, host plants, and insect vectors. In this paper, we report that the cell wall-lacking bacterium Candidatus Phytoplasma mali can alter both the odor of its host plant (apple) and behavior of its vector, the univoltine psyllid Cacopsylla picta. Apple trees infected by this phytoplasma emitted higher amounts of β-caryophyllene when compared to uninfected ones. Psyllids that had no previous contact with Ca. P. mali, as well as infected pyllids, are more attracted by volatiles emitted from phytoplasma-infected apple plants than from uninfected ones. Psyllids that had developed on infected plants without getting infected showed the opposite behavior. These results suggest that the pathogen modifies host plant odor that lures its vector to infected plants. This may result in higher numbers of transmitting vector insects within the population.

Phytopathogen Lures Its Insect Vector by Altering Host Plant Odor

Plant Volatiles as Mate-Finding Cues for Insects.

Chemical communication was shown to play a role in the pear psylla, Cacopsylla bidens. Electrophysiological (EAG) and behavioral responses were investigated in males and females pear psylla . Males were found to be attracted to females, and especially to those on host plants, but not to males, uninfested host plants, or plants infested with conspecific larvae. On the other hand, females were not attracted to males or females but displayed some attraction to host plants. Furthermore, females showed a preference for uninfested pear versus plants infested with conspecific larvae. The antennae of males gave highest electroantenographic response to volatiles from pears infested with females but not males, while females, responded also toward the volatiles of pear alone. These results indicate that females of C. bidens emit sex pheromones that are attractive to the males and suggest that, host volatiles may play a role in host selection by pear psylla females.

Salavat Talebaev

Papers

The role of chemical cues in host and mate location in the pear psylla Cacopsylla bidens (Homoptera: Psyllidae)