How the USDA is Tackling the Citrus Greening Epidemic

What's Being Done to Control Citrus Greening Disease in American Citrus Crops

United States Department of Agriculture Secretary Tom Vilsack says the USDA is reacting to HLB with greater urgency and coordination. Image courtesy USDA

The United States’ citrus crop is in significant danger as we witness more and more crop falling victim to a disease called Huanglongbing (HLB) also known as Citrus Greening or yellow dragon disease. The devastating disease has affected millions of crops across the country in California, Florida, Georgia, Louisiana, South Carolina, Texas and well as Puerto Rico and the U.S. Virgin Islands. The disease-carrying insect has also been found in Alabama, Arizona, Hawaii, and Mississippi.

 Here's what is being done about it.

About Citrus Greening Disease (HLB)

HLB or Citrus Greening disease is transmitted from infected crops to healthy crops by a disease-infected flying insect called the Asian citrus psyllid. About the size of the head of a pin, the psyllid takes the bacteria into its body when it feeds on bacteria-infected plants and then spreads it to healthy plants by injecting the bacterium as it continues to feed. Though the Asian citrus psyllid is primarily to blame, humans do not get off scot-free. Moving infected plants and other plant materials like the leaves of infected plants can also spread the disease. Once infected, the tree is destined for death typically within a few years. With only control methods, we currently do not have a cure. While the disease doesn't threaten humans or animals directly, the impact on citrus crops can be devastating.

Signs of Citrus Greening Disease

It can take up to a year before an infected plant begins to show signs and symptoms of HLB.

Most plants begin to show first signs with the yellowing of the plant's leaves, which can also be indicative of a plant suffering from malnutrition. Lopsided, small fruit that is bitter in taste and contains dark seeds are also signs of Citrus Greening disease. As the disease's name implies, plants whose fruit that remains green even after ripening is also a primary indicator of infection.

HLB is believed to have originated in China in the early 1900s and generally spread by two species of the psyllid. The disease has harmed trees across the world in Asia, Africa, the Arabian Peninsula, and Brazil. There are three identified strains of the bacteria, an Asian, an African, and a recently described American strain discovered in Brazil. The Asian citrus psyllid (Diaphorina citri) has been present in Florida since 1998. 

The USDA's Response to Citrus Greening

With the threat of Citrus Greening potentially devastating America’s $13 billion citrus industry, the United States Department of Agriculture (USDA) has introduced a new unified emergency response framework. The framework's objective is to better position agency response and to provide a more agile, concerted, and direct way to handle both the immediate and long-term needs of the citrus industry. The USDA jumpstarted the program providing $1 million directly to research projects to develop practical, short-term solutions to this problem for growers nationwide.

"USDA listened to the citrus industry's request for more urgency and greater coordination on the response to HLB and is implementing an emergency response structure," said USDA Secretary Tom Vilsack. "Through the Specialty Crop Research Initiative of the Farm Bill, the USDA has provided $9 million in research to blocking the ability of insects to spread HLB to healthy trees." While those first steps were the start, the USDA then urged Congress to pass a new Farm, Food, and Jobs Bill, which it did in 2014. It is clear that the USDA's approach to controlling Citrus Greening spans beyond its own reach to enlist the assistance of other government agencies. 

The USDA's Multi-Agency Coordination System

USDA’s new system is referred to as HLB Multi-Agency Coordination (MAC) System and is supported by several organizations including: USDA’s Animal and Plant Health Inspection Service (APHIS), Agricultural Research Service (ARS), National Institute of Food and Agriculture (NIFA), as well as state departments of agriculture and industry. These aim of these “MAC-Groups” is to prioritize federal research with industry efforts to speed up progress in creating the tools needed for citrus growers to eliminate the HLB problem.

What Else Can Be Done?

Unfortunately, there is no cure for HLB. The only permanent recourse for infected trees and groves is destruction to avoid further spread of the disease. That said, there are other control methods in use, which include the following:

  • Coordinated spraying to kill the disease-carrying psyllid
  • Planting trees inside indoor nurseries to provide protection during vulnerable youth
  • Covering and heating trees
  • Nutritional substances improving resistance
  • Release of a miniature wasp that is a natural enemy of the psyllid

It is clear that it will be up to all involved in the production of citrus crops in the United States from the USDA to individual farmers to temper the negative impact of Citrus Greening.


"Citrus Greening." United States Department of Agriculture: Animal and Plant Health Inspection Service. 

"The Farm Bill." The United States Department of Agriculture. July 2015.

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