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Asian citrus psyllid

The Asian citrus psyllid (ACP), Diaphorina citri, is a phloem-feeding hemipteran insect that feeds on citrus. While the insect causes little damage, it can carry Candidatus Liberibacter asiaticus (CLas), the bacterium that causes the disease huanglongbing (HLB), also known as citrus greening. HLB is the most serious threat to U.S. citrus.

ACP probably originated in India, but it is common throughout citrus-growing regions of Asia. Host plants for ACP are Citrus species and citrus relatives including the curry tree and orange jasmine.

The best way to prevent the introduction of HLB is to prevent the introduction of ACP. Intensive chemical control of ACP is the primary management tool currently being used to reduce ACP populations, but this strategy is costly, and increasingly ineffective. Even intensive pesticide programs have little effect on the spread of HLB, and populations of ACP in Florida are becoming less susceptible to some insecticides. The scientific community is searching aggressively for solutions, and with USDA support, has made advances toward that goal.

Program Information

Asian citrus psyllid (ACP) was first found in the United States in Florida in 1998. In 2001, ACP was found in Texas. By 2008, it was detected throughout the Southeastern United States including Georgia, Mississippi, Alabama, Louisiana, and South Carolina. In the same year, ACP was also detected in California, and in 2009, it was found in Arizona. Currently, all citrus-producing states and territories have ACP.

Asian citrus psyllid (ACP) is a small insect (2.7 mm long) with mottled brown wings. Adults have three distinct abdominal colors: blue/green, gray/brown or orange/yellow. Adults rest and feed on young citrus flush with their bodies held at a 45 degree angle from the plant surface. Females lay approximately 750 eggs over a period of two months under optimal conditions. Because ACP nymphs feed exclusively on young, new shoots, ACP populations fluctuate with the availability of new flush. 

ACP cannot fly very far or sustain a long flight, and therefore spread through a series of short flights.  Long distance spread of ACP occurs through human-assisted movement of this vector on people, farm equipment, and vehicles.

Asian citrus psyllid is found in all citrus producing states in the United States.

APHIS publishes the legal description of current quarantine areas and these can be accessed in the table below.  Users can search by state and pest to determine the quarantine area(s) by state.   

Code of Federal Regulations 301.76

For details on requirements for moving a regulated article, please consult the regulated articles table below. The table is organized by regulated article so users can find the requirements for moving fruit, nursery stock, or other regulated articles. 

The citrus nursery stock protocol provides standards and requirements for the interstate movement of citrus nursery stock from areas quarantined for citrus canker, huanglongbing, and/or Asian citrus psyllid. All interstate movement of citrus nursery stock is prohibited unless the conditions in the protocol are met.

The survey protocol for citrus nursery stock describes the rates of inspection, sampling, and testing required by the nursery stock protocol.

Please contact your local Citrus Health Response Program office if you have questions about the protocol.

Citrus Nursery Stock Protocol

Survey Protocol for Citrus Nursery Stock Protocol

How to Help Save Our Citrus

Asian Citrus Psyllid

Huanglongbing (HLB) is spread by a tiny insect, the Asian citrus psyllid (ACP, Diaphorina citri). First detected in Florida in 1998, ACP spread to Texas in 2001, California in 2008, and Arizona in 2009. ACP is now present in all citrus growing regions of the United States.

ACP reproduce on newly developing leaves, and while the insect itself causes little direct feeding damage, the insect can carry the bacteria that causes huanglongbing (Candidatus Liberibacter asiaticus, CLas). ACP can transmit HLB to uninfected citrus trees as it feeds.

Citrus Black Spot

Citrus black spot (CBS), which is caused by the fungal pathogen Phyllosticta citricarpa (previously known as Guignardia citricarpa) was first found in south Florida, near Immokalee, in March 2010. CBS symptoms on fruit include hard spot, cracked spot, false melanose, freckle spot or early virulent spot, and virulent spot. Symptoms of CBS are easiest to observe during color break, when fruit turns from green to ripe coloration. When trees are severely infected, CBS can cause premature fruit drop before harvest, resulting in significant yield loss.

CBS is spread when wind-borne spores embed in the leaf litter under trees and are carried long distances by air currents. Rain splash may move spores short distances from infected fruit and/or leaf litter. Human-assisted movement of fruit and infected nursery stock is the main form of long distance movement.

Citrus Canker

Citrus canker is a disease caused by the bacterium, Xanthomonas citri subspecies citri. Infection causes lesions on the leaves, stems, and fruit of citrus trees. Typical lesions of the disease are raised, tan to brown in color, and have a water-soaked margin and yellow halos. The bacteria propagate in the lesions, which ooze bacterial cells that are dispersed by windblown rain, contaminated equipment, and movement of infected plants.

While not harmful to humans, uncontrolled canker infection can significantly affect tree health, causing leaves and fruit to drop prematurely. A fruit infected with canker is safe to eat, but its appearance can decrease its marketability.

Canker originated in southeast Asia. Citrus canker was first detected in the United States in 1910 and was eradicated in 1933. It was discovered again in 1995 in Miami-Dade County, Florida. Despite an aggressive tree removal program, USDA was not able to eliminate canker in Florida a second time and ended eradication efforts in 2006.  Canker is present in Florida, Louisiana, and parts of Texas.

Citrus Greening

Huanglongbing (HLB, also known as citrus greening) is the most serious citrus disease in the world and is caused by the bacterium Candidatus Liberibacter asiaticus. There is no cure for this disease once a tree is infected. While the disease poses no threat to humans or animals, it has devastated millions of acres of citrus production around the world, including in the United States.

HLB has been known in Asia since 1900, and Africa since 1920. The first detection of HLB in the Americans was in Brazil in 2004. The first detection of HLB in the United States was in Florida in 2005. HLB has been detected in all the major citrus growing states in the United States, except Arizona.

Once a tree is infected with the bacteria, the tree can remain without detectable symptoms for months or years. During this symptomless phase, the tree can serve as a source of bacteria to infect other trees. Over time, an infected tree will start producing fewer fruit that are smaller, shaped irregulary, and taste bitter. Affected trees have leaves with blotchy mottling, stunted growth, root die-back, and are prone to dropping fruit before it is ripe. Trees infected with HLB will eventually succumb to the disease.

Sweet Orange Scab

Sweet orange scab (SOS) is a disease caused by the fungus Elsinöe australis, which results in scab-like lesions primarily on fruit. The fruit are safe to eat, but the blemishes result in reduced marketability in the fresh fruit market. SOS can cause premature fruit drop and stunt young nursery trees and new field plantings.

SOS was first detected in the United States in 2010 in Texas. SOS is now confirmed in Louisiana, Florida, Mississippi, Texas, Arizona, and parts of California.

Moving citrus trees is the fastest way that citrus diseases are spread. When you move citrus trees, you risk losing America’s citrus.

You Can Help Prevent Citrus Disease

Citrus Story Map

If you think you have identified an infected plant, report it immediately. To avoid spreading the disease, do not move your plant. Complete the "Report It" form below or call your local  USDA State Plant Health Director’s office.

Report It Form (English) 
 Report It Form (Espanol) 

If you are younger than 18 years of age, please ask a parent, guardian or trusted adult to help you complete the form. 

Thank you for helping stop the spread of citrus disease!

Salve los Cítricos: Ayude a eliminar las enfermedades de los cítricos

Save Our Citrus: Put the Squeeze on Citrus Disease






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