What is the Asian citrus psyllid and citrus greening disease or Huanglongbing?

The Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae) is a pest of citrus and close relatives of citrus. Asian citrus psyllid damages plants directly through its feeding activities. New shoot growth that is heavily infested by psyllids does not expand and develop normally and is more susceptible to breaking off. While direct damage is serious, there is even greater concern that the psyllid is an efficient vector of the bacterium that causes the economically devastating disease citrus greening, or Huanglongbing.

Citrus greening disease was first detected in the United States in Florida in 2005. It is found throughout Asia, the Indian subcontinent and neighboring islands, the Saudi Arabian peninsula, and since 2004 in the São Paulo state of Brazil. The citrus greening pathogen is transmitted by psyllid vectors, grafting, and possibly by citrus seed. A disease-free citrus budwood program combined with detection and eradication of Asian citrus psyllid are essential components of the program that protects the California citrus industry from citrus greening disease.

Symptoms of citrus greening include yellow shoots and mottling and chlorosis of the leaves . The mottling superficially resembles zinc deficiency. However, the mottling associated with citrus greening disease does not run only along the veins as in zinc deficiency, but will cross leaf veins. Infected trees are stunted, sparsely foliated, and may bloom off season. In addition, there is twig dieback, leaf and fruit drop, and production of small, lopsided, hard fruit with small, dark, aborted seeds. The juice of the infected fruit has a bitter taste. Fruit do not color properly, leading to the name "greening". Citrus greening is one of the most devastating diseases of citrus in the world.

One of the key measures to slow the spread of citrus greening disease is to observe the quarantine and not transport home grown citrus fruit or plants outside the quarantine area.

University of California Citrus Psyllid Publication

Citrus Research Board Publication

Questions and answers about the Asian citrus psyllid quarantine in San Diego County

Imperial and San Diego Counties Quarantine Area