From the AP:
While Florida farmers have lost much of their crop to cold weather for the second year in a row, they say a fast-spreading, incurable bacteria presents a greater threat to their trees and the citrus industry.
Citrus greening has destroyed groves in the U.S., Brazil, Asia and Africa. Detected in Florida in 2005, it leaves fruit sour, malformed and unusable. Eventually, it kills the tree.
The disease has been particularly devastating because it takes years for citrus trees to reach peak production, and the disease targets young trees, making it difficult for growers to replace those that have been lost.
Trees don't pass the bacteria to each other. Instead, greening — also known as yellow dragon disease, HIB or, in Chinese, Huanglongbing — is spread by insects. There is no cure.