Pattern of stylet penetration activity by Homalodisca vitripennis (Hemiptera: Cicadellidae) adults in relation to environmental temperature and light conditions.
Effects of ambient spring air temperature and light intensity on stylet penetration activities of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar), were studied under field conditions by using an electrical penetration graph. Electrical penetration graph waveforms  representing salivary sheath formation and searching (pathway phase), xylem contact (X waves), and ingestion of xylem fluid (waveform C) were analyzed. Previous research supported the concept that acquisition of Xylella fastidiosa, the Pierce's disease bacterium, occurs during ingestion,  whereas inoculation occurs during xylem contact periods (X waves). Diel patterns of H. vitripennis stylet activity showed that, regardless of light condition, xylem ingestion occurred for the longest duration when temperature remained above the feeding threshold (10°C), and only  occurred at temperatures below the threshold when ingestion was continued from a preceding, warmer time. Regression analysis indicated that mean waveform durations per insect (WDI) for combined stylet activities (pathway and ingestion) as well as X wave frequencies were significantly influenced  by temperature, but there was no significant impact of light intensity or interaction between temperature and light intensity. The relationship between temperature and stylet activities in terms of WDI and X wave frequency was described using linear and nonlinear models. Validation of the  nonlinear models indicated that they well predicted the WDIs for both ingestion and combined stylet activities, using temperature only as a single input. Overall, findings clearly demonstrate that temperature is an important factor that influences the H. vitripennis feeding behaviors  responsible for transmission (acquisition and inoculation) of the Pierce's disease bacterium, with implications for vector ecology and management, as well as disease epidemiology.
Department of Entomology, University of California, Riverside, CA 92521, USA.
Youngsoo
Y
Son
Elaine A
EA
Backus
Russell L
RL
Groves
Marshall W
MW
Johnson
D000818:Animals; D004560:Electricity; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D006430:Hemiptera / Q000502:physiology*; D008027:Light; D016014:Linear Models; D010935:Plant Diseases; D013696:Temperature; D044167:Xylella