Sensory Conditioning in Adult Psyllids

Two experiments were conducted to investigate differences in stimulus acquisition by adult psyllids across sensory modalities. The first experiment evaluated single stimulus conditioning toward a novel, non-host plant associated volatile, vanillin, while the second experiment evaluated single stimulus conditioning to another novel, non-host plant associated stimulus, blue light. In the first experiment, adult D. citri were released onto caged sour orange trees baited with vanillin (Sigma-Aldrich; CAS 121-33-5). Baits were created by adding 5 ml of a 2.5% ethanolic vanillin solution to a cotton wick. Vanillin was dissolved into solution with 100% ethanol. To prevent direct contact by D. citri with vanillin, the wicks were enclosed in perforated plastic cups with lids. One bait cup was placed inside the pot of each sour orange plant. D. citri were allowed to feed freely on the vanillin baited plants for 72 hrs (Fig 1). After 72 hrs, male and female D. citri were assayed for orientation response to vanillin using the Y-tube olfactometry described above. One arm of the Y-tube was baited with 1ml 2.5% vanillin solution on a cotton wick. The other arm was used as a control and was baited with 1 ml of ethanol on a cotton wick. The wicks were air dried for 30 min prior to use to allow the ethanol to fully evaporate. The results of the vanillin experienced D. citri were compared with naïve D. citri.
In the second experiment, adult D. citri (age non-specific) were released onto caged sour orange trees illuminated with blue light (Mood-lites^®; compact florescent, 13W) (Fig 1). D. citri were allowed to feed freely on the blue illuminated plants for 72 hrs. After 72 hrs, male and female D. citri were assayed for orientation response to blue light using modified Y-tube olfactometry. The test treatment arm of the Y-tube was illuminated with blue light as described above, while the control arm was illuminated with white light. The illumination from each light source was isolated by using a solid white divider that was placed between the two arms of the Y-tube, resting upon the crux.
The results of the blue-light experienced D. citri were compared with naïve D. citri. All adult D. citri were at least 4 days old (fully sclerotized and reproductively mature) before use in any part of experiment 2.