Transmission of the frequency components of the vibrational signal of the glassy-winged sharpshooter, Homalodisca vitripennis, in and between grapevines

Authors: Gordon, Shira; TILLER, BENJAMIN - University Of Strathclyde; WINDWILL, JAMES - University Of Strathclyde; Krugner, Rodrigo; NARINS, PETER - University Of California

Submitted to: Journal of Comparative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2019
Publication Date: 8/23/2019
Citation: Gordon, S.D., Tiller, B., Windwill, J., Krugner, R., Narins, P. 2019. Transmission of the frequency components of the vibrational signal of the glassy-winged sharpshooter, Homalodisca vitripennis, in and between grapevines. Journal of Comparative Physiology. 205:783-791. https://doi.org/10.1007/s00359-019-01366-W.
DOI: https://doi.org/10.1007/s00359-019-01366-W

Interpretive Summary: Finding ways to cope with agricultural pests is an ongoing problem. Insects become resistant to pesticides and pesticide use is limited to certain times of year for application. One pest of major concern is the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, which is a pest of grapevines in California. The GWSS can carry a bacterium, Xylella fastidiosa, in its mouth, thereby acting as a vector where it infects grapevines with the bacteria that can kill the plants in two to three years. Recent work has delved into developing a new technique that uses vibrations mimicking GWSS natural calls as a pesticide-free method of control. While the method works, there is still much that is unknown about the mechanism. This study tested propagative properties of the GWSS vibrational signal using specific frequencies (e.g., 100 to 900 Hz) found in the communication call of GWSS. The study measured vibrational propagation over distances up to 50 cm and across gaps in non-touching plants up to 10 cm. The results indicate that higher frequencies lose intensity, yet travel faster over distances. In addition, low frequencies (e.g. 100 Hz) but not higher frequencies (e.g. 900 Hz) can propagate between plants not in physical contact with one another. Together, the results indicate that the GWSS vibrational signal changes over distances. This change in the signal is thought to provide information to the animals about distance and location of the source. Understanding signal propagation properties is important for manipulating the GWSS signal used to control this pest.

Technical Abstract: The agricultural pest, the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, relies primarily on vibrational communication through plants. Males and females engage in a vibrational duet for species identification, location, and courtship. The GWSS vibrational signal exhibits a dominant frequency between 80 and 120 Hz, with higher-frequency, lower-intensity harmonics occurring approximately every 100 Hz. However, previous research revealed that not all harmonics are present in every recorded signal. Therefore, how the GWSS vibrational signal changes as it travels through the plant was investigated. The data confirmed that overall signal intensity decreases with increasing distance from the source. In addition, at distances of 50 cm, differential propagation was detectable, with higher frequencies traveling faster, and thus, arriving earlier than lower frequencies. Finally, the GWSS generates no detectable airborne signal, yet the low vibrational frequencies are detectable in neighboring plants as a result of leaf-to-air-to-leaf propagation. For instance, 100 Hz was detected with at least a 10-cm gap between leaves, whereas 600 Hz was detectable only with a 0.1-cm gap. Together, these results highlight complexity of vibration signal propagation in plants and suggest the possibility of using the harmonic content of the signal to determine distance to the signaling GWSS source.