Published: Jan 19, 2011 4:50 PM EST
Updated: Jan 19, 2011 1:51 PM EST

VERO BEACH, Fla. (AP) - Florida farmers say the biggest threat to their citrus crop isn't the recent cold weather. They're more worried about greening.

 The incurable disease has wiped out trees in the U.S., Brazil, Asia and Africa. It was first found in Florida in 2005.

 The bacteria that causes greening is spread by an insect. The disease leaves fruit sour and malformed and, eventually, kills the tree.

And, in a cruel twist of fate, young trees seem most vulnerable, making it hard for farmers to replace those they've lost.

Hundreds of researchers from more than a dozen countries converged on Orlando last week to talk about the disease. There was one hopeful announcement: Scientists recently assembled the genome sequences for two citrus varieties that may reveal why trees are susceptible to greening.

(Copyright 2011 by The Associated Press. All Rights Reserved.)