Yellow Dragon Disease

The state of Florida is facing a serious threat to its citrus crop, one that could potentially wipe out its entire citrus industry. The threat is called, Yellow Dragon disease, more commonly known as citrus greening. If more research isn’t done and a cure found, the Florida citrus industry might not even have a decade of good citrus production left in its groves.

Citrus greening is a bacterial disease. Bacteria are injected into a citrus plant by a tiny winged insect known as a citrus pysllid. Citrus pysllids are tiny insects, only 3-4mm, but their wrath is great. The insects suck on citrus branches, spreading the bacteria through saliva contact. They also feed on the leaves of the plants. Young pysllids prefer to eat the new growth of the plant. These insects leave tell tale signs of their visit in a white, waxy excretion left on the branches, of a now infected tree.

The disease is spread mainly by pysllids, although scientists have recently discovered that grafting and the use of dirty tools might also spread the disease. Humans and animals are not affected by the disease.

Trees don’t show symptoms of the disease immediately after being infected. It might take up to two years for a tree to show symptoms. Some signs of infection include: leaf yellowing and molting of leaves, in the beginning, then dieback, poor flowering and misshapen, bitter fruits occur. In the final stage, the disease blotches citrus branches in yellow pattern much like that of a dragon, hence the name of the disease. In some areas where the disease is endemic trees might live five years after planting, not living long enough to produce edible fruit.

The disease is commonly called Haunglongbing in Asia where the citrus pysllid is a native insect and has gradually destroyed orange groves in India for decades. The disease was first discovered in the early 1900’s but citrus pysllids are thought to have arrived in the United States around 1998.

When the insect was initially discovered in Florida, eight counties were infected. Today 31 counties are infected. The entire state of Florida’s citrus plants are under quarantine as are all the citrus plants in Hawaii, Guam, Puerto Rico and several counties in Texas.

There is no known cure for Yellow Dragon disease. Scientists are working to control the spread of the disease by eradicating infected trees and host plants of the disease need to be treated prior to being planted in a grove where greening is occurring. Residents are encouraged to inspect their citrus trees and report any suspicious damage to their local agriculture extension.

Craig Meyer, Florida’s deputy agriculture commissioner has been quoted as saying, “The threat of Yellow Dragon disease is serious.” His department’s goal is to figure out how to contain the disease, maintain healthy groves and start growing disease resistant trees, with a special emphasis on eradicating the citrus psyllids altogether.