Citrus greening is a very serious issue and has the potential to wipe citrus out of Florida and other states. Florida is already seeing a huge decline in citrus production. The groves near where I work have been turned in to planned developments or abandoned (the fruit is left to rot).
USA Today article form 2007 on greening:
Disease threatens Fla. citrus industry - USATODAY.com
From the web:
In which direction is Florida headed?
In 1998, Florida had 785,900 acres of trees that produced 13,583 tons of citrus.
Last year, Florida had 554,400 acres of trees that produced 7,236 tons of citrus.
Florida Citrus Industry Fights for Survival A1A South