Plant Protection and Quarantine Pest Alert November 2010 Get the Facts on Citrus Greening (Huanglongbing) 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 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–Infected 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 Visit www.aphis.usda.gov/ many citrus relatives (e.g., orange and employer. citrusgreening for the most jasmine, limeberry, and trifoliate current quarantine information. orange) are susceptible to citrus 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..