Keep Leprosis From Re-entering Florida

Citrus leprosis has not been reported in Florida since 1968, but researcher Ozgur Batuman called it “an approaching threat to Florida citrus” in a recent virtual seminar. Batuman, a citrus pathologist at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Southwest Florida Research and Education Center, urged growers to be on the lookout for the disease.

According to Batuman’s presentation, the disease in recent years has spread northward from South America though Central America and is now established in Southern Mexico. He said it threatens all of the Caribbean islands as well as the citrus-growing areas within the United States. In South America, citrus leprosis is in Paraguay, Brazil, Argentina, Uruguay, Venezuela, Bolivia and Colombia. Central American countries with the disease are Panama, Costa Rica, Guatemala, Nicaragua, El Salvador, Honduras and Belize. Hawaii is the only U.S. state that currently has the disease.

In Florida, where citrus leprosis was first reported in the 1860s, it was called “scaly bark” due to the damage it did to bark, Batuman said.

Citrus leprosis is a non-systemic viral disease that causes chlorotic lesions on citrus leaves, fruit, twigs and branches. The causal virus agents are transmitted by species of Brevipalpus mites, also known as flat mites or false spider mites, which exist in major U.S. citrus-growing areas. Batuman said all active stages of the mite — larvae, nymph and adult — can acquire and transmit the virus. Sweet oranges and mandarins are the varieties mainly affected by the disease.

Other citrus leprosis effects include lower fruit quality, premature leaf and fruit drop, decreased foliar area and branch death. Untreated trees eventually die.

Controlling the mites that spread the disease is the primary means of citrus leprosis management, Batuman reported. He added that it is also important to avoid bringing propagation materials from areas infected with the disease into Florida. He urged growers who think they might have the disease in their groves to report their suspicions to the Florida Department of Agriculture and Consumer Services or a UF/IFAS Extension specialist.

Batuman also addressed HLB and phytophthora diseases in his presentation.

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