Associative learning of host-plant chemical cues in immature glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae)

• Author(s): Patt, Joseph; S?tamou, Mamoudou;
• Abstract: We determined whether Homalodisca vitripennis nymphs can associatively-learn to recognize olfactory stimuli produced by host plants, and evaluated the relative importance of olfactory conditioning in host-plant recognition. To provide nymphs for testing, second- to fourth instars were placed on cowpea (Vicia unguiculata) sprigs for 1.5 days. The cut-ends of the sprigs were immersed either in hydroponic solution containing a low concentration of vanilla extract, or, as a control, in hydroponic solution alone. After removal from the sprigs, the nymphs responsiveness to a pale green disk in the presence of vanilla extract odor was tested in an olfactometer using no-choice tests. In preliminary tests with blank air, 44% of nymphs from the control group jumped to the pale green target, demonstrating that innate attraction to this color is low. Vanilla extract constituents were detected by gas chromatography-mass spectrometry analysis of ethanolic extractions made from vanilla-treated cowpea sprigs. Nymphs that fed on plant sprigs with vanilla-flavored xylem fluid were significantly more attracted to the pale green target than nymphs that fed on control sprigs with non-flavored xylem fluid. However, there was no difference between individuals in the experimental and control groups with respect to the amount of time they required to orient- and jump to the visual target. The finding that nymph response to a non-attractive color was enhanced following ingestion of a novel flavor indicated that immature GWSS are capable of olfactory conditioning. Rapid population growth of GWSS may depend on the close proximity of host plants suitable for successful juvenile development. Therefore, understanding the mechanisms by which nymphs locate their host-plants is fundamental to developing vegetation management programs aimed at suppressing their population growth and dispersal in complex landscapes.
• Publication Date: Jan 2007
• Journal: Journal Of Insect Behavior