Monday, December 11, 2006

Correlations of cibarial and precibarial muscle activities with EPG waveforms and excretion in the smoke-tree sharpshooter, Homalodisca liturata (Hemiptera: Cicadellidae)

Sébastien Dugravot,, University of California - Riverside, Department of Entomology, University of Riverside, Riverside, CA and Elaine Backus,, USDA San Joaquin Valley Agricultural Research Center, 9611 S. Riverbend Ave, Parlier, CA.

The smoke-tree sharpshooter, Homalodisca liturata, like its close relative, the glassy-winged sharpshooter, H. coagulata, is a generalist xylophagous leafhopper known to be a vector of Xylella fastidiosa. The stylet penetration behavior of sharpshooters in plants is most rigorously studied via electrical penetration graph (EPG) techniques. Using electromyography (EMG) recordings, AC EPG monitoring, and video analysis, we investigated which parts of the EPG waveforms can be directly attributed to muscle activities involved in sharpshooter feeding. We first showed that the C waveform, corresponding to xylem ingestion, is the perfect reflection of the activities of the cibarial dilator muscles. Second, precibarial valve muscle activities occur during Pathway Phase, supporting that they may be associated with the B1s waveform, proposed to be involved in X. fastidiosa inoculation. Third, correlations were made between number of cibarial pumps and excretory droplet production during sustained ingestion. This study is relevant to better understanding of how X. fastidiosa is inoculated into plants.

Species 1: hemiptera Cicadellidae Homalodisca liturata (smoketree sharpshooter)
Species 2: Hemiptera Cicadellidae Homalodisca coagulata (glassy-winged sharpshooter)