Transmission Parameters for Candidatus Liberibacter asiaticus by Asian Citrus Psyllid (Hemiptera: Psyllidae)

Abstract

The purpose of this investigation was to evaluate acquisition and inoculation (together, transmission) efficiency of Candidatus Liberibacter asiaticus (Las), the pathogen associated with citrus huanglongbing (HLB) by the Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae). In laboratory studies, nymphs reared on Las infected plants were more likely to acquire the bacterium than adults. Acquisition by nymphs ranged from 60 to 100%, whereas acquisition by adults only reached 40% after 5 wk of feeding on Las-infected plants. Similar rates of pathogen acquisition by psyllids after nymphal and adult feeding were observed in the field. Transmission of Las from parent to offspring (transovarial) occurred at a rate of 2-6%. One year after psyllid inoculations, successful transmission by individual D. citri ranged from 4 to 10%, whereas groups of 100 or more D. citri transmitted the pathogen at a rate of approximately 88%. In addition, the proportion of Las-positive adult psyllids, determined using quantitative real-time polymerase chain reaction, decreased over time when held on healthy plants. Due to the low rate of pathogen acquisition and long time period required for successful inoculation by adult D. citri, experiments designed to determine the latent period required for replication and successful inoculation of Las by D. citri did not result in Las-infected plants after >1 yr of incubation after inoculation. Collectively, these results indicate that adult D. citri which acquire the HLB pathogen as adults are poor vectors of the pathogen compared with adults that acquired the pathogen as nymphs.