Tuesday, July 10, 2012

The Greening of Florida Citrus

orange treesWhen the Florida Dept. of Agriculture reported in 2005 that Citrus Greening had infected residential trees in Palm Beach and Martin counties, a University of Florida Extension Horticulture Agent commented that if on a scale of one to 10, Citrus Canker is a three, then Citrus Greening is an “imperfect” 10. Although the disease poses no threats to humans or animals, diseased trees can die within five to eight years and bear unusable fruit.

Many of us will recall the Citrus Canker eradication program begun in January 2000 when the state Dept. of Agriculture adopted a policy of removing all infected trees and all citrus trees within a 1,900 foot radius of an infected tree in both residential areas and commercial groves. By 2006, the program was suspended after the U.S. Dept. of Agriculture declared that eradication was not practical.

Citrus Green Affects State’s Economy, Too

In a study released earlier this year, the University of Florida found that Citrus Greening disease, also know as Huanglongbing (HLB) or yellow dragon disease, cost the state’s economy more than $3.6 billion in the last five years and with it eliminated more than 6,600 jobs. Caused by a bacterium, the disease attacks the plant’s vascular system and once infected, there is no known cure.

Control Can Be Challenging

The disease is transmitted by the Asian citrus psyllid, an insect no larger than the head of a pin. The infected insect spreads the disease as it feeds on the leaves and stems of citrus trees. an insect, the citrus psyllid. It can then be spread by grafting and field dodder, a type of parasitic weed.

Control of Citrus Greening can be challenging because:

  • The citrus psyllid is widespread
  • The frequency with which people move infected host plant material
  • Diseased trees may not show symptoms for several years,
    and
  • All varieties of citrus are susceptible and the psyllid feeds on a wide variety of host plants
Signs and Symptoms

Early symptoms of Citrus Greening are small yellow leaves on one limb or section of the tree canopy. The most diagnostic symptoms are mottling that often ignores the leaf veins. The newest leaves may show symptoms resembling zinc deficiency, while older leaves have a characteristic greening mottle. Other symptoms are yellow shoots, twig die-back, poor flowering and stunting. Although symptoms can provide strong clues to the presence of Citrus Greening disease, the Florida Dept. of Agriculture Div. of Plant Industry advises that final confirmation by molecular diagnostic tools is needed for regulatory purposes.

Quarantine

Currently, all citrus and citrus psyllid host plant material in Miami-Dade, Broward and Palm Beach counties is under quarantine. Shipments to citrus producing areas outside the state of Florida is prohibited. Shipping within the state of Florida is allowed only through a signed compliance agreement with the Florida Dept. of Agriculture, Div. of Plant Industry. More information is available at the department’s website: http://www.freshfromflorida.com/pi/.

Management

There is no place in the world where Citrus Greening is well established that it is under completely successful management. The Florida Dept. of Agriculture advises that the best management programs are integrated, making use of regulatory measures to ensure completely clean planting stock, cultural practices to ensure timely removal of infected plants and chemic and biological control of psyllid vectors.

For more information on Citrus Greening – including program updates, factsheets, regulatory actions, control and testing protocols, and links to other sites, visit: http://www.aphis.usda.gov/plant_health/plant_pest_info/citrus_greening/index.shtml

The trained experts at Insect Protection Pest Control are also available to further advise you on Citrus Greening disease as well as other diseases affecting your citrus trees. Call now for a FREE consultation.

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