黄龙病是柑橘类植物的严重疾病。由不能培养之细菌 Candidatus liberibacter 引起，通过木虱在株间传染。染病树目先见黄叶，青果，然后逐渐枯萎。此病传染力强，患株无药可治，可将果园尽毁。于1929年最先于南中国见记载，后传遍华南。1951年传入台湾，对当地柑桔类种植造成致命打击。现时传遍亚洲、非洲及巴西，对各地柑橘类种植皆造成破坏。1998年后亦于美国佛罗里达州出现。

黄龙病在各国曾经有不同称谓。现正式称为"HuangLongBing"，因中国农业学家林孔湘最先于1950年代对此病之成因、防治作出科学硑究。

Citrus greening disease (Chinese:黄龙病; pinyin:huánglóngbìng; literally: "Yellow Dragon Disease"), abbreviated as HLB, is a disease of citrus caused by a vector-transmitted pathogen. The causative agents are motile bacteria, Candidatus Liberibacter spp. The disease is vectored and transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama, and the African citrus psyllid, Trioza erytreae Del Guercio, also known as the two-spotted citrus psyllid. It has also been shown to be graft-transmissible. Three different types of HLB are currently known: The heat-tolerant Asian form, and the heat-sensitive African and American forms. The disease was first described in 1929 and first reported in China in 1943. The African variation was first reported in 1947 in South Africa, where it is still widespread.