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Citrus Greening: Existential Threat to Florida’s Citrus industry

March 13, 2013

PrintFive Hundred Years of Florida Flora Firsts: How Plants have shaped Florida’s History

In calling for increased funding for research on citrus greening, Florida Commissioner of Agriculture Adam Putnam recently cited the plant disease as an “existential threat” to Florida’s citrus industry. Experts warn the disease, also known as HLB or Huanglongbing, threatens to change the face of Florida’s iconic citrus industry, and that adverse change could occur within the next five years.

Florida’s citrus industry has been scrambling to retard the spread of HLB since its discovery in the state in 2005. Despite the best efforts of growers, the Florida Department of Agriculture and Consumer Services and the United States Department of Agriculture, however, greening has spread to all counties where citrus is grown commercially.

citrus greening grapefruit

Citrus greening disease (HLB) causes fruit to be misshapen, like this grapefruit.

Greening has compromised citrus production wherever it has appeared.  First reported in Asia during the late 1800s it has devastated citrus production in Asia, Africa, the Arabian Peninsula and Brazil. It has now killed millions of citrus plants in the southeastern United States and threatens to spread across the entire country.

Once plants are infected, there is no cure. Where the disease is endemic, citrus trees produce green, misshapen, bitter, inedible fruit. Most infected trees die within a few years.

HLB is caused by a bacterium that is spread (vectored), in the Asian form, by the Asian citrus psyllid, Diaphorina citru Kuwayama, which is no bigger than the head of a pin. It can also spread through plant grafting and movement of infected plant material. It cannot be spread by humans, animals, equipment, wind or rain.

Since it was first discovered in Florida, greening has spread to all counties where citrus is grown commercially.

How did HLB get to Florida?

The Asian citrus psyllid was found for the first time in the U.S. in 1998 in Delray Beach, Fla., but no associated HLB infection was found at that time. Agriculture officials imposed quarantines and took other actions to control the spread of the psyllid. However, with the abundance of citrus and other hosts present in the state, psyllid populations grew and became established.

Aware of the potential threat HLB posed to the state’s citrus industry, the Florida Department of Agriculture and Consumer Services Division of Plant Industry had been conducting HLB surveys for years. With the discovery of the Asian citrus psyllid, survey efforts intensified.

greening leaf

Discoloration of leaves is one symptom of citrus greening (HLB). The disease almost always results in the death of infected trees.

In a cooperative effort between the state and USDA, targeted surveys were initiated in communities with concentrations of people from countries where HLB is endemic, because those areas were thought to be at a higher risk of receiving infected plant material.

In 2005, a targeted HLB survey in South Florida identified two citrus trees showing symptoms of HLB. Laboratory tests confirmed the Asian form of HLB.

Managing citrus diseases

Agriculture officials have responded to the establishment of HLB, citrus canker and other citrus diseases through the Citrus Health Response Program (CHRP), an overarching effort that involves standards for citrus inspection regulatory oversight, disease management and education. Efforts include training growers to identify citrus diseases and manage psyllids. The program is designed to provide protection at every level of production.

  • Registration is required for producers, production units, nurseries, budwood facilities, harvesters, packing houses and processors.
  • Surveys are conducted to verify compliance with requirements for fruit harvesting. Nursery stock is now produced in insect-proof structures with strict production facility specifications.
  • Fresh fruit certification allows tracking of fruit, property, phytosanitary documentation, packing house post-harvest inspection and treatment monitoring.
  • The program also implements disease management strategies for fruit production systems and dooryard citrus.

The department, with agreement from the USDA, is relying on the best science available to determine disease control actions. As data is gathered, control activities may be adjusted.

Natural control helpful, but not solution by itself

Reducing psyllid populations with natural enemies can limit losses due to HLB. The department, in conjunction with the University of Florida, has imported a parasitic wasp, Tamarixia radiata, from Asia, and released it into Florida. This wasp, has become established in Florida and, along with other native natural enemies, has reduced the population of Asian citrus psyllids. However, it will not eliminate the psyllid.

What can the public do?

The public plays an important role in protecting Florida’s natural environment and plant life. Home gardeners who suspect their trees may be infected with HLB should call the FDACS-DPI Toll free Helpline, 1 (888) 397-1517 or their county Extension office. If it is determined the tree is infected, the tree should be destroyed before it infects other citrus in the area.

Here are some important actions individuals can take to help protect agriculture and the environment:

  • Purchase only from registered nurseries.
  • Be vigilant. If you see signs of disease or an unusual pest, contact your county Extension office or the FDACS/DPI Helpline, 1 (888) 397-1517.
  • “Don’t Pack a Pest.” When returning home to Florida from a trip, declare agricultural products in luggage and do not bring plants, fruits, vegetables or illegal animals.
  • Ask for advice. Contact your county Extension office or visit http://www.doacs.state.fl.us/pi for tips on caring for citrus trees or managing citrus diseases.
  • Consider planting alternative fruit trees. Your county Extension office can make recommendations, or visit http://www.doacs.state.fl.us/pi

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During 2013, this blog will focus on some plants that, for better or worse, have helped form the history of our state. We will be drawing on expertise of our DPI scientists and we invite everyone to participate. We welcome your questions and comments.

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