Monitoring and characterization of DC electrical penetration graph waveforms of tea green leafhopper, Empoasca onukii , on tea plants

The tea green leafhopper, Empoasca onukii (Homoptera: Cicadellidae), is a serious pest of “Yabukita”, the most popular tea cultivar in Japan. This study investigated its stylet-probing behavior with a direct current (DC) electrical penetration graph (EPG) system. The EPG signals were classified into four distinct waveforms according to amplitude, frequency, voltage level and electrical origin. The waveforms were then characterized by fast Fourier transformation. The waveforms were correlated with distinct feeding behaviors: Np, non-probing, when stylets were not inserted; Eo1, putative pathway and channel-cutting phase, when stylets were inserted but not ingesting sap; Eo2, putative phloem phase, when the leafhoppers were probably ingesting from phloem; and Eo3, putative non-phloem phase, when the leafhoppers were probably ingesting from mesophyll. Mean durations of waveforms showed that E. onukii likely ingested plant fluid mainly from phloem and partly from mesophyll. The description of DC EPG waveforms associated with feeding behaviors of this serious pest constitutes a fundamental step toward the understanding of the resistance mechanisms of the host plants against herbivorous insects.