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Pest Alert Plant Protection and Quarantine
November 2010
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2010 Get the Facts on Citrus Greening 4 \\
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University of Florida-IFAS, Jamie Yates University of Florida-IFAS, Jamie Yates USDA, R. Anson Eaglin
Figure 1-Citrus greening-affected trees may Figure 2-Trees infected with citrus greening Figure 3-Tiny to the naked eye, adult Asian
take years to die from the disease. In this produce bitter, misshapen fruit. Here, the citrus psyllids are no bigger than common
image, an infected citrus tree displays multiple asymmetrical development and aborted seed gnats.
symptoms of citrus greening, including twig in this fruit are telltale signs of citrus greening.
dieback, leaf mottling, leaf yellowing, fruit
drop, and poor fruit color.
Citrus greening disease, or detected in the United States bodies are grayish-tan with brown
huanglongbing, is one of the in August 2005 in Miami-Dade markings and mottled brown
world’s most serious citrus County, FL, citrus greening is wings. The last two segments of
diseases. There is no known now established throughout their antennae are black. They
cure for citrus greening. While most citrus-producing counties feed with the posterior of their
not a threat to human health, in Florida, and the entire State bodies raised at a 45-degree
citrus greening greatly reduces is under Federal quarantine for angle (fig. 3). When disturbed,
citrus production. Once infected citrus greening and Asian citrus they typically jump or fly a short
with the disease, citrus trees psyllid. Federal law prohibits the distance. They are most likely to
usually decline within 5 to 12 movement of live citrus plants, be found on new shoots, or young
years (fig. 1), whereas healthy plant parts, budwood, or cuttings growth, of citrus plants.
commercial citrus trees are outside of Florida. Subsequent In nymph form, Asian citrus
typically productive for more than U.S. detections of the disease psyllids’ oval-shaped bodies are
50 years. Trees infected with have occurred in numerous yellowish-brown. Difficult to
citrus greening produce bitter, citrus-producing States and U.S. see, nymphs cannot fly, and they
misshapen, unmarketable green Territories. The most current move slowly. Most visible are
fruit (fig. 2). information on disease-affected the waxy, white excretions they
Because there is no cure for areas in the United States can be produce (fig. 4).
this disease, the U.S. Department found online at www.aphis.usda. Asian citrus psyllid eggs are
of Agriculture (USDA) prohibits gov/citrusgreening. yellow/orange in color and shaped
citrus plants and plant material like almonds. They are often
from moving outside of areas How It Spreads tucked inside crevices and leaf
where citrus greening is present folds.
and restricts the movement of the Citrus greening is spread primarily Not all Asian citrus psyllids
same material from areas where by gnat-sized insects called Asian carry the disease-causing
the Asian citrus psyllid, a primary citrus psyllids (Diaphorina citri bacteria. But even non-infected
vector of the disease, is present. Kuwayama). These invasive pests psyllids can damage citrus
Citrus greening is believed transmit the disease to citrus trees plants and trees by stunting the
to have originated in China in and other host plants when they growth of new shoots. On host
the early 1900s. It has greatly feed on the leaves and stems. plants and trees, these psyllid
reduced citrus production Adult psyllids resemble aphids infestations result in burned
in all countries where it has in appearance, measuring about shoot tips and twisted leaves on
become established. First one-eighth of an inch. Their new growth. New shoots that are
ra
USDA, R. Anson Eaglin USDA, Hilda Gomez Taiwan Agricultural Research Institute, Hung Shih-Cheng
Figure 4-One of the clearest indications of an Figure 5-Trees infected with citrus greening Figure 6-lnfected fruit is discolored,
Asian citrus psyllid infestation is the presence may express numerous symptoms, including misshapen, and bitter.
of psyllid nymphs and their white, waxy blotchy mottling and corky veins in leaves.
excretions on citrus plants.
heavily infested by psyllids do not shoots. The newest leaves may How You Can Help
expand and develop normally, display symptoms that can be
and they are more susceptible to misdiagnosed as signs of zinc To report suspect disease
breaking off. Insect populations deficiency. Older leaves take symptoms or psyllid insect
increase during periods of active on the mottling characteristic sightings, please contact your
plant growth. of greening. Other symptoms State department of agriculture
Citrus greening can also be include twig dieback and poor or the plant-disease diagnosis
transmitted by grafting diseased flowering. clinic at your State’s land-grant
budwood. Although the citrus Fruit from diseased trees university. Do not transport plants
greening pathogens are bacteria, is small and often misshapen. you suspect to be infected with
the disease does not spread Typically, some green color citrus greening or infested with
by casual contamination of remains even on ripe fruit (fig. Asian citrus psyllids, as this may
personnel and tools or by wind 6). Greening-affected fruit spread the disease and violate
and rain. tastes bitter, medicinal, and State and Federal quarantines.
In June 1998, Asian citrus sour. Seeds usually abort
psyllids were discovered in (fail to develop), and fruit set Learn More
backyard plantings of orange (formation) is poor. Symptoms
jasmine in Palm Beach County, vary according to the time of For more information on citrus
FL—the first detection of this infection, stage of the disease, greening, please visit
pest in the United States. tree species, and tree maturity. www.SaveOurCitrus.org
Currently, psyllids are located in or www.aphis.usda.gov/
more than a dozen States and Host Plants citrusgreening.
U.S. Territories. These areas
are under a Federal quarantine. Nearly all citrus species and USDA is an equal opportunity provider
and employer.
Visit www.aphis.usda.gov/ many citrus relatives (e.g., orange
citrusgreening for the most jasmine, limeberry, and trifoliate
current quarantine information. orange) are susceptible to citrus USDA
greening. Sweet orange and
Symptoms mandarin orange are highly United States Department of
susceptible to the disease; sour Agriculture
Animal and Plant Health
Trees and plants that are infected orange, grapefruit, and lemon are
Inspection Service
with citrus greening disease may moderately susceptible.
not show symptoms for years. Greening-susceptible citrus Program Aid No. 1851
As the disease moves within plants may serve as reservoirs Revised November 2010
the tree, it is not uncommon for for citrus greening disease.
whole branches, and eventually However, because all citrus plant
the entire tree, to turn yellow species are potential hosts for
progressively. One of the most Asian citrus psyllids, all citrus
characteristic foliage symptoms plants are significant pathways
of citrus greening is blotchy by which infected psyllids can
mottling (fig. 5) of the leaves spread to areas that are not
and yellowing of leaf veins and infected with citrus greening.
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