Citrus is one of the top three fruit crops worldwide.Citrus production is facing an unprecedented crisis due to Huanglongbing (HLB,also known as citrus greening),which is the most devastating disease of citrus.HLB was first reported in Asia a century ago.HLB is associated with Candidatus Liberibacter asiaticus (Las),Ca.L.americanus (Lam),and Ca.L.africanus (Bové,2006),which belong to the gram-negative α-proteobacteria.Among them,Las is the most widely spread.Las and Lam are vectored by Diaphorina citri Kuwayama (ACP),whereas Laf is transmitted by Trioza erytreae.HLB and ACP are rapidly spreading to and having a devastating impact on citrus production in other citrusproducing areas such as Brazil,Caribbean counties,and the US.To date,HLB has been confirmed in 51 of the 140 citrusproducing countries.The major citrus-producing regions without HLB,such as the Mediterranean region and Australia,are at great risk for ACP establishment and HLB spread (Gutierrez and Ponti,2013).In addition,Trioza erytreae has been found in Spain and poses immediate threat of spread of HLB in the Mediterranean region.Thus,HLB has become a global problem.