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

Abstract

Asian citrus psyllid (Diaphorina citri) transmits Huanglongbing, a devastating disease that threatens citrus trees worldwide. A better understanding of the psyllid’s host-plant selection process may lead to the development of more efficient means of monitoring it and predicting its movements. Since behavioral adaptations, such as associative learning, may facilitate recognition of suitable host-plants, we examined whether adult D. 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 and their response to neutral visual cues was enhanced by chemosensory stimuli. Conditioned psyllids were sensitive to the proportion of chemosensory components present in binary mixtures. Naïve 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.

Male Psyllids Differentially Learn in the Context of Copulation

“…After 24 h, the males were removed and individually assayed for response to vanillin. Previous research indicated that vanillin was a suitable volatile for use in learning assays with D. citri [36,51]. …”

UV reflective properties of magnesium oxide increase attraction and probing behavior of Asian citrus psyllids (Hemiptera: Liviidae)

“…A completely randomized choice assay was used to study the probing of D. citri in response to chemosensory stimuli (odorants and/or tastants) as described previously 6,38,51 . This assay measured insect orientation within a screened cage to combinations of color and texture, and subsequent probing behavior that may result from a combination of olfaction and gustation upon contact with a wax substrate containing magnesium oxide or barium sulfate.…”

“…To visualize salivary sheaths produced by feeding attempts on the wax beads, cover slips were removed from the cages and beads were stained with Coomassie blue dye for 60 sec for yellow SPLAT beads and 45 sec for white beads, washed in water and allowed to air-dry 6,38,51 . The number of salivary sheaths in each bead was counted under a stereomicroscope at 50 X magnification.…”

Female mate preference in an invasive phytopathogen vector: how learning may influence mate choice and fecundity in Diaphorina citri

“…For this reason, there is significant need to understand the biology and ecology of this pest species. Previous research has demonstrated that learning plays a role in ecology and behavior of D. citri (Patt et al., ; Stockton et al., , ). Male and female D. citri readily associate novel olfactory and visual stimuli with specific host plant genotypes and appear to prefer the host species with which they have had previous feeding experience (Stockton et al., ).…”