Diane Nelson, UC Davis
In an orange grove outside Exeter, California, workers climb aluminum ladders to pick fruit with expert speed. California produces 80 percent of the nation’s fresh oranges, tangerines and lemons, most of it in small Central California communities like these.
“This may be the last place in the world where you can still grow citrus,” says farmer Richard Bennett, reaching high to pull an orange from a tree. He peels it in two long ribbons, and the scent of zest fills the air. “Citrus is so important to our health and economy, and it’s threatened by a devastating disease.”
The disease is called huanglongbing or HLB—more commonly known as citrus greening. It has decimated groves in Asia, Brazil, the Dominican Republic and Florida, and is now spreading in California.
Citrus greening can move with alarming speed. In Florida, the disease was first detected in 2005. Fourteen years later, orange production has fallen by more than 75 percent, and grapefruit production is down 85 percent. Backyard citrus has virtually disappeared in some areas.