Citrus greening, also known as Huanglongbing or HLB, is one of the worst citrus diseases in the world. Bacteria (Candidatus Liberibacter asiaticus) spread by the Asian citrus psyllid (Diaphorina citri) infect citrus trees, first causing leaf discoloration, then defoliation and twig dieback, followed by root loss and eventually tree death. Fruits are stunted, misshapen, and often have a (you guessed it) green color, making them useless, even for juice. The disease can also be moved on wood and leaf tissues but not on commercial (i.e., washed and cleaned) fruit.
In the past decade, citrus greening has caused a 21 percent reduction in fresh citrus fruit and 72 percent decline in orange production in the U.S. Florida is the largest orange-producing state in the U.S. and has seen a 74 percent decline in citrus production. No matter which metric you use, citrus greening is a devastating disease to citrus in this country and worldwide.
HLB is currently present in Florida, Georgia, Louisiana, South Carolina, California, Texas, Puerto Rico, and the U.S. Virgin Islands. The psyllid vectors have been detected in many other southern states as well as Hawaii and the Caribbean islands.
Scientists have widely accepted management recommendations for citrus greening, including preventative pesticide sprays and removal and destruction of infected material. With a threat this severe, you’d think it would be easy to get all the growers together, on the same page, and have them implement a coordinated management plan. Turns out, however, that’s not always the case, as detailed in a new paper published last week in the open-access Journal of Integrated Pest Management.