The movement and spread of nymphs of Diaphorina citri Kuwayama on host plants

Huanglongbing (HLB) is a serious citrus disease worldwide. Diaphorina citri Kuwayama( Hemiptera: Psyllidae) is the insect vector of Candidatus Liberibacter asiaticusand Ca. L.americus,two bacteria associated with HLB in Asia and South America,respectively. Both adults and late stage nymphs of D. citri can transmit the bacteria. This paper presents the transfer and spread of D.citri nymphs among the young shoots of healthy and HLB- infected citrus. The result showed that late stage psyllid nymphs( 3rd to 5th instar) could make horizontal and vertical transfer among young shoots.On HLB- infected citrus,the speed of transfer was slower than that on the healthy citrus. The density of the nymphs is also a factor affected to the transfer speed. Nymphs transfer faster with the density increased. Psyllid nymphs preferred young shoots of HLB- infected citrus. It was observed that on healthy citrus,more psyllid nymphs transferred downwards to the trunk base. This study confirms the transfer and spread of D. citri nymphs and the effect of HLB- infected citrus. It provides reference for D. citri and HLB prevention and control.