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Title: Innate and conditioned responses to chemosensory and visual cues in Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), vector of Huanglongbing pathogens

Author
item Patt, Joseph - Joe
item STOCKTON, DARA - University Of Florida
item Meikle, William
item SETAMOU, MAMOUDOU - Texas A&M University
item AGENOR, MAFRA-NETO - Isca Technologies, Inc
item Adamczyk, John

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2014
Publication Date: 11/19/2014
Citation: Patt, J.M., Stockton, D., Meikle, W.G., Setamou, M., Agenor, M., Adamczyk, J.J. 2014. Innate and conditioned responses to chemosensory and visual cues in Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), vector of Huanglongbing pathogens. Insects. 5(4):921-941.

Interpretive Summary: Asian citrus psyllid is a tiny insect that transmits Huanglongbing, aka citrus greening, a devastating disease that threatens citrus trees worldwide. This psyllid reproduces only on the young leaves of citrus and it close relatives, such as orange jasmine and curry leaf. We know very little about how its behavior influences its selection of host-plant. An understanding of the host-plant selection process may lead to the development of more efficient means of trapping and monitoring the psyllid and predicting its movements. Since behaviors, such as learning, may facilitate recognition of suitable host-plants, we examined whether psyllids could learn to recognize colors and aromas from both host and non-host-plants. Their responsiveness to the test colors and aromas was measured as the number of times they tried to feed on a line of wax containing the test stimuli. Of the several aromas tested, the psyllids learned to recognize two of them. They could also learn to blue, a color they are not normally attracted to. The psyllids showed strong innate, or instinctual, responses to several test aromas, such as limonene, an essential oil which has a lemony aroma and is emitted by many of the psyllid’s host-plants. While innate responses are probably the psyllid’s primary behavioral mechanism for selecting host-plants, learning may enhance its ability to select suitable host-plants during changes in the seasons and when they disperse to new habitats.

Technical Abstract: Asian citrus psyllid (Diaphorina citri) transmits the causal agent of Huanglongbing, a devastating disease that threatens citrus trees worldwide. This psyllid oviposits and develops only on the emerging shoots of its rutaceous host-plants; however, little is known about the mechanisms underlying its host-plant selection behavior. An understanding of the host-plant selection process may lead to the development of more efficient means of trapping and monitoring the psyllid and predicting its movements. Since behavioral adaptations, such as associative learning, may facilitate recognition of suitable host-plants, we examined whether adult Diaphorina citri could be conditioned to visual and chemosensory stimuli from host and non-host-plant sources. Response was measured as the frequency of salivary sheaths, the residue of psyllid probing activity, in a line of emulsified wax on the surface of a test arena. The psyllids displayed both appetitive and aversive conditioning to two different chemosensory stimuli. They could also be conditioned to recognize a blue-colored probing substrate. The results confirmed those of an earlier study showing that the presence of olfactory cues enhanced psyllid response to neutral or weakly stimulating visual cues. Psyllids conditioned to one compound displayed a diminished level of probing when that compound was mixed with another test compound, showing that they are sensitive to the proportion of chemosensory components presented to them. The psyllids displayed strong to moderate innate biases to several of the test compounds. While innate responses are probably the psyllid’s primary behavioral mechanism for selecting host-plants, conditioning may enhance its ability to select host-plants during seasonal transitions and dispersal.