ARS | Publication request: STYLET PENETRATION BEHAVIORS OF GRAPHOCEPHALA ATROPUNCTATA (SAY): EPG WAVEFORM CHARACTERIZATION AND QUANTIFICATION

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 7, 2004
Publication Date: July 1, 2004
Citation: Almeida, R.P., Backus, E.A. Stylet penetration behaviors of graphocephala atropunctata (say): epg waveform characterization and quantification. Annals of the Entomological Society of America. 97(4):838-851 (2004)

Interpretive Summary: We quantified and statistically analyzed the feeding behaviors of the sharpshooter leafhopper Graphocephala atropunctata (Signoret) on grapevines with an AC (alternating current) electropenetration graph (EPG) monitor. We identified waveforms that represent pathway phase, i.e. when the stylets (the piercing-sucking mouthparts) are moving towards the target tissue for ingestion including secretion of the salivary sheath, as well as waveforms probably representing ingestion from xylem, mesophyll and phloem. A total of 68 % of the 20 hour monitoring periods for all insects was spent in stylet penetration, and only a small proportion of that time was spent in pre-ingestion (i.e. pathway) behaviors. We found that few changes in behavior occurred once an event of stylet penetration (i.e. probe) had started This species apparently does not ingest exclusively from xylem, but occasionally from mesophyll or possibly phloem also. The size of grape leaves used for the assays directly influenced the amount of time insects ingested from xylem and/or mesophyll tissues. Information from this work establishes benchmarks for future research addressing the mechanisms of X. fastidiosa transmission and sharpshooter ecology.

Technical Abstract: We analyzed the probing (a.k.a. stylet penetration) behaviors of the sharpshooter leafhopper Graphocephala atropunctata (Signoret) on grapevines with an AC (alternating current) electropenetration graph (EPG) monitor. We identified waveforms distinctive for stylet penetration pathway phase, putative xylem, mesophyll and phloem ingestion. A total of 68 % of the 20 hour monitoring periods for all insects was spent probing, and only a small proportion of that probing time was spent in pre-ingestion behaviors. Number of waveform events (different identified behaviors) per probe for each waveform type was low, varying from a mean of 1 to 2.43, suggesting few changes in behavior occurred once a probe had started. Conditional probability analysis supported that hypothesis, since insects usually terminated a probe and began a new one after ingestion-related events, rather than repeating in the same probe the previously performed waveforms. The size of grape leaves used for the assays directly influenced the amount of time insects ingested from on xylem and/or mesophyll tissues.