Huanglongbing, also known as the Citrus Greening Disease, or literally 'Yellow Dragon Disease', is a very serious disease on citrus.
HLB is a disease caused by Gram-negative bacteria. This kind of bacteria has a thick capsule, which can better resist the natural environment and is conducive to survival. The germs invade the phloem and are transported, and the germs invading the plant at any position will cause the whole plant infection from the leaves to the roots. Huanglong disease is different from other diseases. It not only infects the whole body, but also penetrates into the phloem. There is almost no cure for it, and it can even destroy the orchard in severe cases.
HLB is vectored and transmitted by the Asian citrus psyllid, Diaphorina citri. The HLB disease bacteria can multiply in citrus psyllids, so the psyllids can carry it for life and can carry the bacteria anywhere they emerge. Once citrus psyllids appear in the orchard, they will very likely to bring HLB to the citrus. Asian citrus psyllids reproduce quickly in large numbers, and feed frequently, even disease-resistant varieties cannot defend against such attacks for a long time. The larvae of the citrus psyllids secrete wax to protect themselves, block the damage of insecticide, and reduce the efficacy of spraying.