A citrus disease that has killed millions of trees and cost growers billions of dollars around the world has been detected in California. The USDA last week confirmed the huanglongbing disease had been discovered in a lemon-grapefruit hybrid in Los Angeles County, potentially putting California’s $2 billion citrus industry in jeopardy.

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Huanglongbing, also known as Yellow Dragon Disease, is carried by psyllid lice and has infected citrus plantations from South Africa to China. The bacterial disease was first described in 1929 and first reported in China in 1943. It affects the tree’s vascular system, producing bitter fruit and eventually killing the tree.

Following the discovery in a residential area of Los Angeles County, sales and shipments of citrus trees within a 5-mile radius of the infected have been suspended.

State and industry officials have pledged to start work on setting up a larger quarantine zone. A programme for containment of the disease has been in place since 2008, after huanglongbing spread to the United States; it is estimated to have cost the Floridan citrus industry $3.6 billion since it was detected there in 2005.

Although the disease has affected citrus crops for over 50 years in various parts of the world, there are no biological or genetic controls to combat it, although USDA scientists are currently examining a number of antibiotics as potential treatments for infected citrus plants based on positive results observed in treating infected periwinkles.

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