ELECTRICAL RECORDING OF PLANT PENETRATION BY WESTERN POWER THRIPS

Plant penetration by western flower thrips (Frankliniella occidentalis (Pergande)) was analysed with the electrical penetration graph techni que (EPG, DC-system). Thrips attached to a gold wire were included in an electrical circuit to record EPGs when penetrating the plant tissue s with their stylets. Three basic EPG waveforms have been distinguishe d, correlated with stylet penetration into cells, salivation, and inge stion, respectively. The main difference with EPGs of Homoptera is the occurrence of continued separate penetrations that are not necessaril y followed by ingestion. Insertion of the stylets causes strong voltag e fluctuations in the EPG. We could confirm earlier evidence that pene tration of cells and subsequent ingestion of (part of) the protoplast takes less than 20 seconds. Repeated short penetrations can be followe d by a continuous feeding pattern during which the stylets are not wit hdrawn. The same sequence of waveforms is produced on other plant part s such as fruits or pollen grains. The specific waveforms are mainly c aused by electromotive force (emf). The emf component was recorded wit h high resolution and the correlation of waveform details with activit ies of the cibarial muscle system is discussed.