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On the Lookout for Mite-Borne Citrus ThreatBy Luis Pons
March 11, 2004
A mite-borne plant disease moving slowly north from South America is on the radar screen of many scientists, including those at the Agricultural Research Service's Systematic Entomology Laboratory (SEL) in Beltsville, Md.
They're concerned that citrus leprosis, a virus that substantially damaged Florida's orange crop early last century, will once again affect U.S. citrus growers. They're out to stop it by focusing on its vector: flat mites of the genus Brevipalpus.
SEL's mite expert, entomologist Ronald Ochoa, says the disease's presence in Central America has caught the attention of U.S. Department of Agriculture scientists at ARS and at the Animal and Plant Health Inspection Service (APHIS). ARS is the USDA's chief scientific research agency.
Mite species believed to be capable of spreading the disease are already abundant in Florida, California and Texas, three states that are the backbone of the U.S. citrus industry. SEL scientists are collaborating with the Florida Department of Agriculture and Consumer Services to clarify differences among the Brevipalpus species implicated as leprosis vectors. This work is part of a wider project--funded in part by USDA's Foreign Agricultural Service and APHIS, and led by University of Florida acarologist Carl C. Childers--seeking to minimize the virus's impact.
Symptoms of citrus leprosis include small, chestnut-brown spots commonly referred to as "nailhead rust" that appear on fruits, leaves and green twigs of afflicted trees. The resulting tree canopy growth loss and premature fruit and leaf drop reduce plant productivity.
During its previous outbreak, the virus had spread to 17 Florida counties by 1925 before being eradicated by several factors, including citrus growers planting in new locations and controlling mites with sulfur. The overuse of sulfur can kill citrus trees.
Read more about this research in the March issue of Agricultural Research magazine.