Citrus disease scares Florida growers

GAINESVILLE, Florida, September 12, 2005 (ENS): A bacterial plant disease that could endanger Florida's $9 billion citrus industry has been found for the first time in the United States, agriculture officials said Friday. The disease affects the vascular system of plants and causes infected trees to die in a few years.

"Symptoms of citrus greening disease are similar to plants with severe nutritional deficiencies including yellow shoots, twig dieback, tree decline and reduced fruit size and quality."
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) confirmed the first U.S. detection of Liberibacter asiaticus, or citrus greening, on pummelo tree leaf and fruit samples collected, tested and submitted by the Florida Department of Agriculture and Consumer Services (FDACS).

The samples were collected from two separate locations in the Homestead, Florida area and after initial testing in the USDA's Gainesville laboratory, were sent to APHIS for confirmatory testing.

Using several different tests, APHIS’ National Plant Germplasm and Biotechnology Laboratory in Beltsville, Maryland, confirmed the samples were infected with the bacterial disease, which already affects citrus in India, Asia, Southeast Asia, the Arabian Peninsula and Africa. The disease does not pose a threat to human health.

Citrus greening, or huanglongbing, attacks the vascular system of plants. Once infected, there is no cure for a tree with citrus greening disease. In areas of the world where citrus greening is endemic, citrus trees decline and die within a few years. There are three forms: Asian, African and Brazilian. The strain found in South Florida appears to be the Asian form.

The bacteria are transmitted primarily by insect vectors, citrus psyllids, and through infected planting materials. In June 1998, the insect that carries the Asian strain of citrus greening, Diaphorina citri Kuwayama, was found for the first time in the United States in Delray Beach, but no citrus greening infection was found at that time. Because of the extreme threat to Florida citrus, the Department has been conducting a citrus greening survey for many years. Once the Asian citrus psyllid was discovered in 1998, citrus greening survey efforts were intensified.

The diseased trees were found in Homestead by an entomologist with the Florida Division of Plant Industry during a Cooperative Agricultural Pest Survey, part of a cooperative effort between the state and APHIS.

Communities with concentrations of people from countries where citrus greening is endemic may be at higher risk of receiving infected plant material, and these areas have been targeted in survey activities, APHIS said.

State and federal officials will begin a comprehensive survey of the area to identify the extent of disease spread. A team of experts, including scientists, state and federal agricultural officials and academia, has been established to quickly mobilize a response.

“We are assessing the situation to determine exactly what course of action will be taken. We will provide the citrus industry and public with information as soon as it becomes available,” said FDACS Commissioner Charles Bronson.

A joint science panel is being convened by APHIS and FDACS to obtain expert advice on the most effective surveillance and control strategies based on the current detection. If the disease was discovered early enough, eradication may be possible.

Symptoms of citrus greening disease are similar to plants with severe nutritional deficiencies including yellow shoots, twig dieback, tree decline and reduced fruit size and quality, often affecting only a single branch at first. Older leaves develop a characteristic mottling, or patches of discoloration. The inside of the fruit is lopsided and is inedible due to poor taste. The fruit drops off before ripening and has poor color.

Where the disease exists, management strategies rely on preventing its spread into uninfected areas by regulating the movement of propagating material, destruction of infected trees, and control of insect vectors.

Copyright Environment News Service (ENS) 2005. All Rights Reserved.

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