August 2 - NCPN-Hops Tier 2 Meeting
2:00 - 5:00 PM PST (In-person and Zoom); contact Tanner Hunt at tanner.white@wsu.edu for additional details
August 2 - NCPN-Hops Tier 2 Meeting
2:00 - 5:00 PM PST (In-person and Zoom); contact Tanner Hunt at tanner.white@wsu.edu for additional details
The Threat
of HLB
Huanglongbing (HLB), also known as citrus greening, is a devastating citrus disease. HLB was first observed in Asia more than 100 years ago and now is, by far, the most serious threat to the citrus industry worldwide. It is currently jeopardizing the commercial viability of the citrus industry in the United States (graph below for Florida citrus production).
HLB is associated with the phloem limited bacterium ‘Candidatus Liberibacter asiaticus’ (CLas) and is vectored by the insect, Asian Citrus Psyllid (ACP). HLB causes many symptoms; early in the disease leaves develop a blotchy mottle appearance. Later, the fruit of an infected tree becomes inedible and the canopy and roots dieback and eventually the tree dies. HLB- infected trees become unproductive within 2 to 4 years after the onset of the disease and young trees that become infected typically do not reach a productive age. The cost for treating an endemic grove is high, as spray and removal of infected trees and those near them are likely needed. There is no cure for HLB, and all types of citrus and cultivars are affected - oranges, lemons, grapefruit, mandarins, tangerines and others.
Growers, nurseries, scientists, and the government are diligently working to slow the spread of this disease, but they cannot do it without your help. It is incredibly important to buy trees only from local reputable licensed nurseries and remove and destroy trees that have tested positive for HLB. Every infected tree has the potential to spread the disease to healthy trees, increasing the spread of the disease within and across citrus orchards and residential properties. It is in the best interest of the public and the citrus producers, small and large, conventional, and organic to collaborate with the HLB inspectors and have their trees inspected and tested to remove and properly dispose of all HLB infected trees.
Huanglongbing (HLB) symptomatology. A) Yellow shoot. B) No
symptoms. Citrus leaves from HLB negative trees. C) Blotchy mottle. Citrus leaves from HLB positive trees with yellow discolorations appearing in nonsymmetric patterns. D) No symptoms. Citrus crop from HLB negative trees. E) Citrus greening. Citrus crop from HLB positive trees with uneven fruit
coloration and the reduced fruit size. F) No symptoms; normally maturing citrus fruit with color break (orange) initiating at the stylar end progressing upwards to the green stem area of the fruit. (G) Color inversion. HLB affected fruit with color break inverted with stylar end (arrow) remaining green while the stem area of the fruit is already orange. H) Lopsided fruit; longitudinal section of deformed HLB affected citrus fruit. I) Lopsided fruit
and aborted seeds; cross section of deformed HLB affected citrus fruit with aborted seeds (arrow). Photos by G. Vidalakis and S. Halbert.
Economic Impact of HLB
Controlling HLB is a costly and challenging endeavor for citrus growers. To combat the disease, they must invest in frequent insecticide spraying to control the Asian citrus psyllid, which spreads HLB. This requires significant resources, including increased pesticide use: Frequent spraying of insecticides (every 7-15 days) to control the psyllid population, higher production costs: More expensive fertilizers and inputs to mitigate the effects of HLB and intensive monitoring: Regular monitoring of trees for signs of infection and testing for HLB. These costs add up quickly, impacting citrus production and the economy in several ways: Increased tree mortality rates: HLB can lead to rapid decline and death of infected trees, reduced marketable yield per tree: Infected trees produce smaller, misshapen fruit, reducing marketable yield and higher production costs: Increased pesticide use, monitoring, and research expenses.
The impact of HLB varies depending on factors like: Tree age: younger trees are more susceptible to HLB, tolerance: Some trees may have natural tolerance to HLB and environmental conditions: Weather, soil quality, and other environmental factors can affect HLB spread.
To combat HLB, the citrus industry has implemented various measures, including Nursery regulations: Nurseries must move production under protective structures to prevent psyllid infestation, eradication programs: Infected trees are removed to prevent disease spread and research initiatives: Scientists are working to develop new treatments, resistant tree varieties, and more effective management strategies. These efforts aim to mitigate the economic burden of HLB and ensure the long-term sustainability of the citrus industry.
Impact of HLB in California
California is the primary source of lemons for the US fresh fruit market, and the spread of HLB into commercial citrus groves could significantly impact lemon production and the overall citrus industry. While HLB has not been detected in commercial citrus trees in California, the Asian citrus psyllid (ACP), the primary vector for HLB, has been found in both residential and commercial trees. With over $145 million of annual production value at risk, understanding disease transmission rates, effective management practices, and farmer cooperation is crucial to addressing HLB.
HLB has been detected in urban areas, with over 1,650 infected trees, and the Asian citrus psyllid (ACP) is present throughout California's citrus-producing regions. To combat this threat, significant efforts and funding ($40-45 million annually) are being dedicated to anti-ACP-HLB programs to protect the state's $7.2 billion citrus industry. The Citrus Research Board is dedicating most of its resources to battling ACP and HLB to ensure the sustainability of California citrus.
Impact of HLB in Florida
For the last 40 years, Florida citrus production trends have been variable—weather events and diseases have caused short- and long-term production changes. Hurricanes and freezes have played a significant role in the fluctuations in production, but HLB has had a profoundly detrimental impact on the industry. The first report of HLB in Florida occurred in 2005 in a private residence in South Florida and by 2013, 100% of commercial orchards were HLB positive (Gottwald 2010, Graham et al. 2024). The effects of HLB have been devasting for the state’s citrus industry. The total acreage of oranges and grapefruits decreased by approximately 55.6% from 2004 to 2023, falling from 748,555 acres to 332,256 acres. Florida, ranking second in citrus production nationwide, has experienced a significant decrease of over 80%, dropping from 13.5 million tons in 1998 to approximately 2.6 million tons in 2021. The economic loss due to HLB effects in Florida from 2015 to 2020 was estimated to be over $1 billion annually (Li and Wu 2020). Oranges comprise 95% of Florida’s citrus production which is predominantly processed for juice, but the disease negatively impacts juice quality and quantity. Since 2004, there has been a 92% decrease in the gallons per box of fresh chilled juice from 60 gallons to approximately 4.74 gallons per box in 2024. The industries that support Florida’s citrus productions, such as packing houses and processing plants, have drastically decreased by approximately 90% since the onslaught of the disease.
Effects of HLB on Florida | Before HLB | After HLB | % Change |
|---|---|---|---|
Number of Grapefruit trees * | 14 million | 5 million | -64% |
Number of Orange trees * | 80 milllion | 60 million | -25% |
Number of Packing houses + | 79 | 26 | -67% |
Number of Juice processing facilities + | 41 | 14 | -66% |
Number of Citrus growers * | 7,389 | 2775 | -62% |
Number of Citrus bearing acres * | 679,000 | 387,100 | -43% |
Sources: *U.S. Department of Agriculture-National Agricultural Statistics Service. + Florida Department of Agriculture & Consumer Services
Impact of HLB in Texas and Arizona
The Texas citrus industry has a statewide economic impact of over $469 million. Following the first report of HLB in Florida in 2005, efforts were made to implement state and federal quarantine measures to prevent the movement of potentially infected plant materials. The measures included the transition from open-field to enclosed nursery systems, the implementation of an area-wide psyllid control, surveys for HLB and ACP in commercial groves and residential sites, and removal of confirmed infected trees. Despite these efforts, HLB detection sites in Texas increased to 26% and 40% of commercial groves and residential sites, respectively, by 2017 (Ref. #9). Such a rapid disease progress despite efforts and investment to slow the disease spread underscores the enormous challenges posed by HLB once introduced into a new area.
At present, Arizona remains ACP infested but with no HLB finds.
