As if the real-estate bust hadn't wreaked enough havoc on Florida, farmers say abandoned lots left behind by would-be developers have become a breeding ground for a plague that is killing thousands of the state's orange trees.

A type of tiny lice known as the Asian citrus psyllid has made its home in the orchards, spreading a disease known as citrus greening, or yellow dragon disease, which causes trees to produce shriveled, bitter oranges before killing them. Since being spotted in 2005, the disease has spread to all parts of the state. And with no known cure, citrus greening is threatening to cripple a $9 billion-a-year industry that supplies 90% of U.S. orange juice.

"It's been one uppercut after another," said Jackie Burns, interim director of the Citrus Research Education Center in Lake Alfred, Fla., which has studied the outbreak. She said she has no doubt that "grove abandonment" has helped spread the disease.

The U.S. Department of Agriculture says millions of acres of crops have been devastated by the disease in the southern U.S.

Marty McKenna, a farmer in Polk County in the central part of the state, is battling the disease in many of the 6,000 acres that he owns or manages. He has had to spend thousands of dollars on pesticides, which he said are only partly effective, to prevent the disease. Where he has failed, he has burned hundreds of infected trees and replanted.