Feeding behavior of Diaphorina citri and its transmission of "Candidatus Liberibacter asiaticus' to citrus

Huanglongbing (HLB), also known as citrus greening, is currently the most destructive disease of citrus, responsible for huge economic losses in the world's major citrus production areas. The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), transmits Candidatus Liberibacter asiaticus' (Clas), the pathogen responsible to cause HLB. Understanding of vector, pathogen, and host plant interactions is important for the management of this vector-disease complex. We used the direct-current electrical penetration graph (DC-EPG) system to evaluate feeding behavior of Clas-infected D.citri adults, and their potential to transmit the pathogen to healthy citrus, Citrus reticulata Blanco cv. Sunki (Rutaceae), following a 24-h inoculation access period. Plants were tested for the presence of Clas by qPCR 6months after inoculation. Findings suggest that inoculation was associated with salivation into the phloem sieve elements (waveform E1). The minimum feeding time for successful transmission by a single adult was 88.8min, with a minimum E1 duration of 5.1min. Regression analysis indicated a significant relationship between E1 duration and transmission efficiency. The adults successful in transmitting Clas to healthy citrus were able to penetrate and feed in the phloem much earlier than those which did not transmit. The minimum duration of E1 for a female was shorter than that of a male, but transmission was higher. However, durations of other EPG parameters were not significantly different between male and female. Feeding by single Clas-infected D.citri adults on 6-month-old plants (Sunki) resulted in 23% HLB-positive plants 6months after inoculation. Multiple nymphs or adults could transmit the pathogen more efficiently than individual adults in the field, and further enhance the severity of the disease. Effective tactics are warranted to control D.citri and disrupt transmission of Clas.