Citrus Greening - Huanglongbing (Yellow Dragon Disease): A New Threat to Florida Citrus

Citrus Greening, a potentially devastating disease to the Florida citrus industry, was identified in Miami-Dade County in early September 2005. Since then, additional cases have been confirmed in Broward, Palm Beach and St. Lucy counties. More serious than citrus canker, diseased trees can die within 5 to 8 years and bear unusable fruit. Here are some important facts to know:

• Citrus Greening is caused by a bacterium, (Liberibacter asiaticus) and attacks the vascular
  system of plants.
• Once infected, there is no known cure
• There are three known strains of the disease: Asian, African and Brazilian. The strain found is
  South Florida appears to be the Asian strain.

Citrus greening is transmitted by an insect vector, the citrus psyllid (Diaphorina citri). It can also possibly be transmitted by grafting and field dodder, a parasitic weed; but does not seem to be transmitted through casual contamination such as personal tools, wind, or rain like citrus canker. Asian citrus psyllids were first found in South Florida in 1998 and have since become dispersed across the state. The insect feeds on a variety of plants including some important ornamentals.

Control of citrus greening will be particularly challenging because:

• The insect vector, citrus psyllid, is widespread
• The frequency with which people move infected host plant material
• Diseased trees may not show symptoms for several years (1 to 5 years or more)
• All varieties of citrus are susceptible and the psyllid vector feeds on a wide variety of host
  plants including the common Orange Jasmine (Murraya paniculata)

Click for Quarantine Notice
Asian citrus psyllid adult
citrus psyllid nymph

For the citrus greening pest alert and Information http://doacs.state.fl.us/pi\

Citrus Greening website

Citrus Greening Hotline 1-800-850-3781

Identification of Citrus Greening:

Symptoms of citrus greening disease can be recognized by the foliar and fruit symptoms which are similar to plants with severe nutritional deficiencies including:

• Yellow shoots, twig dieback and tree decline
• Older leaves develop a characteristic mottling or patchy discoloration
• Veins are often prominent and yellow
• Fruit from infected plants has poor color and bad flavor; reduced size
• Severe fruit drop

C. greening mottle in pummelo

• Mimics zinc deficiency on new leaves
• Mottled pattern on older leaves
• Notched leaf from Asian citrus psyllid feeding

**Quarantine Notice**

Currently, due to the direct exposure of citrus greening disease in South Florida, all citrus and citrus psyllid host plant material, including orange jasmine (Murraya paniculata), in Miami-Dade, Broward, and Palm Beach counties, is under quarantine. Shipments to citrus producing areas, outside the state of Florida (e.g. Arizona, California, Louisiana, Texas, Puerto Rico, etc.) is prohibited. Shipping within the state of Florida is permissible only through a signed compliance agreement with the Florida Department of Agriculture and Consumer Services, Division of Plant Industry. Terms of the compliance agreement must be followed explicitly and require all host plant material be treated with an EPA-approved insecticide labeled for use in commercial ornamental nurseries. You must use a drench 10 days prior to shipment and a foliar spray 2 days prior to shipment. Here is a list of approved products:

Drench Foliar Spray Marathon Tame* Marathon II Dursban* Chlorpyrifos Pro 4*

*These products are Restricted Use pesticides and subject to the requirements in Chapter 487 F. S. and Rule 5E-9

Follow all applicable directions, restrictions and precautions. Remember, the label is the law. For more information about the citrus greening compliance agreement, visit the Florida Department of Agriculture & Consumer Services website at http://doacs.state.fl.us/pi\. Also provided is a list of plants known to carry citrus greening and a list of plants known to be hosts for the insect vector. In addition to the compliance agreement, each shipment of host plant material needs to be certified by an authorized representative of the Florida Department of Agriculture and Consumer Services Division of Plant Industry. Once certified, a permit will be issued allowing shipment of the plant material. Note: no shipments will be allowed to stock dealers such as Home Depot, Lowes, Target, etc.

Information provided in this article was obtained by the Florida Department of Agriculture Division of Plant Industry and the United States Department of Agriculture Animal and Plant Inspection Service

Prepared by:
Michelle Leonard, Program Assistant, Broward County Michael Orfanedes, Ph.D., Commercial Horticulture Agent III

Photography credits: Jeffrey Lotz, Dr. Susan Halbert and Dr. Xiaoan Sun, Division of Plant Industry