Characterization of the Probing and Feeding Behavior ofPlanococcus citri(Hemiptera: Pseudococcidae) on Grapevine

18 páginas, figuras y tablas estadísticasThe citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), is a vector\udof Grapevine leafroll-associated virus 3 (GLRaV-3), which causes severe damage to grapevines (Vitis\udspp.) worldwide. We studied the feeding behavior of P. citri on grapevine leaves and whole plants\udinfected with GLRaV-3 and on artiÞcial feeding membranes using DC-electrical penetration graphs\ud(EPGs). P. citri ingested from phloem sieve elements, but it also spent long intervals in the xylem.\udWaveforms, not described before for mealybugs, were characterized, some of them resembling those\udof aphids: 1) one new pattern occurring within the phloem phase, named E23, correlated with\udhoneydew excretion and positive ninhydrine reaction and therefore was associated with sap ingestion\udfrom the phloem sieve elements; and 2) an extracellular waveform, named G, also possibly associated\udwith ingestion in artiÞcial membranes, which probably represented xylem ingestion. The potential\uddrops (pd) of P. citri showed two distinct phases (pd1 and pd2).Theoccurrence of pds was, on average,\udless frequent than in aphids (0.14/min), but they lasted much longer (32.5 s). The temporal analysis\udof 20 EPG recordings on detached leaves lasting 20 h showed great variability among individuals. Only\ud11/20 mealybugs reached the phloem phase, and ingestion from the phloem sieve elements (E23) was\udthe predominant phloem-related activity. However, the G pattern was even more frequent, and most\udinsects (16/20) showed xylem ingestion activities with an average duration of 8.7 h. This work\udrepresents the Þrst step to identify speciÞc stylet activities associated with the acquisition and\udinoculation of GLRaV-3 by P. citri.Fundacion Caixa Galicia. This project\udwas supported by the Spanish Ministry of Education and\udScience (AGL2005-01449/AGR).Peer reviewe