The disease, known as "citrus greening" or huanglongbing, is caused by a bacterium, Candidatus Liberibacter asiaticus. The bacteria are spread from tree to tree by a tiny insect called the Asian citrus psyllid, The New York Times reports.
A tree affected by citrus greening may not show symptoms for years. Eventually, however, the leaves turn yellow and fall, while the tree's fruit fails to mature, falling to the ground prematurely before the tree slowly dies. [Image Gallery: A Rainbow of Fall Leaves]
"We have got a real big problem," Vic Story, a lifelong Florida citrus grower, told The Times. "It's definitely the biggest threat in my lifetime, and I'm 68. This is a tree killer."
There is no known cure for citrus greening (which also affects grapefruit, lemons and other citrus crops), despite the best efforts of numerous research labs. The Candidatus bacteria is so devastating to citrus crops that it was classified as a bioterror weapon in 2003, The New Yorker reports.
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