Living With Huanglongbing

Huanglongbing is a devastating disease of citrus known as “Yellow Dragon Disease” in Asia and as “Citrus Greening” disease in the US. The disease is caused by a bacteria of the genus, Candidatus Liberibacter. The bacteria infest the citrus trees and cause yellowing of the leaves, thus the name “Yellow Dragon”. The fruit of infected trees often fails to turn color and remains green, thus the name “Citrus Greening”. The bacteria impart a bitter taste to the fruit, making it unsuitable for marketing. There is no cure for infested trees, they must be cut down and replaced. Citrus Greening is a problem in Florida and Georgia and in Central American countries. In some areas, Citrus production may become unprofitable because of the disease.

The primary insect vector is the Asian Citrus Psyllid, Diaphorina citri. First reported in Florida in 1998, the psyllid carries the bacteria between plants. The bacteria infests many plants in the citrus family including ornamentals such as orange jasmine the plant where Asian Citrus Psyllid was first discovered. Orange jasmine is commonly sold by large box stores as an ornamental and appears to be important in the spread of Asian Citrus Psyllid.

Asian Citrus Psyllid
Photo: Michael E Rogers, University of Florida

Currently the United States maintains quarantines to prevent nursery stock shipments from areas infested by Huanglongbing and Asian Citrus Psyllid. In areas with Asian Citrus Psyllid and Huanglongbing, citrus growers must vigilantly inspect their plants to remove all infested trees that can be reservoirs of disease. Asian Citrus Psyllid is controlled primarily by pesticide treatments augmented by cultural and biological control methods. Psyllid control is necessary to stop the spread of the disease to uninfected trees.

As the numbers of invasive species in the US have increased with increasing trade, the economic and environmental impacts of these species are increasingly important. A good program for detection and prevention of pests from entering pest-free areas and quarantine of pest infested areas is an essential component of modern trade.