Abstract: 【Aim】 The Asian citrus psyllid, Diaphorina citri, is the vector of huanglongbing (Candidatus Liberibacter asiaticus) which is the most destructive disease of citrus. Spraying the horticultural mineral oil (HMO) on the citrus canopies can reduce the feeding behavior and oviposition of D. citri efficiently. This study aims to explore how HMO within plant tissues influences the feeding behavior of adult D. citri. 【Methods】 The aqueous emulsions of an nC24 HMO were diluted into different concentrations (0.25%, 0.5%, 1% and 2%, v/v), and sprayed to the immature pomelo (Citrus grandis) leaves. The leaves sprayed with clear water were served as the control. The probing and feeding behaviors of D. citri adults on the citrus leaves were recorded for 12 h and transformed to the waveform signal by a Giga-8 DC-EPG, and then the waveform parameters of every treatment were analyzed and compared. 【Results】 The percentages of duration of C waveform (pathway waveforms) of D. citri adults on the citrus leaves sprayed with different concentrations of HMO were significantly higher than that of the control. Spraying different concentrations of HMO reduced the percentage of duration of E2 waveform (phloem sap ingestion), while had no significant influence on the percentages of duration of D (first contact with phloem tissue), E1 (saliva secretion into phloem) and G (xylem sap ingestion) waveforms as compared to the control. The waveform duration per adult (WDI) of the C waveform in HMO treatment groups was significantly longer than that of the control, but showed no significant difference among different treatment concentrations. The WDI of D waveform in HMO treatment groups was significantly shorter than that of the control. The WDI of the E1, E2, and G waveforms decreased significantly with the increasing of the HMO concentration. Spraying 2% HMO significantly reduced the WDI of E1, E2 and G waveforms as compared to the other treatment concentrations. In the HMO treatment groups, the number of probes per adult and the number of various waveform events per adult were significantly decreased, and were the lowest in the 1% and 2% HMO treatment groups. The waveform duration per event per adult (WDE) of np (non-probing waveform), D and E2 waveforms in the HMO treatment groups was significantly shorter than that of the control. The WDE of D, E1 and E2 waveforms in the 2% HMO treatment group was significantly lower than that in the other treatment concentrations and the control. The 2% HMO treatment delayed the time from mouthpart contact with leaf to the first probe and the time to the first E1 of D. citri adults. 【Conclusion】 The results revealed that applying 2% HMO to citrus leaves not only decreased the feeding duration and frequency of D. citri adults, but also significantly reduced the time of salivation in phloem and ingestion of sap. Therefore, HMO is worthy of application in the integrated pest management of citrus huanglongbing disease and D. citri. We preliminarily speculated that HMO likely inhibits or covers the volatile substances on the leaf surface of citrus by entering into plant stomata and preventing the release of plant volatile substances, thus reducing the feeding of D. citri on the host.

Key words: Diaphorina citri, horticultural mineral oil, huanglongbing, feeding behavior, electrical penetration graph