Overview of Citrus Greening in Allen Morris

Transcription

1 Overview of Citrus Greening in 2014 Citrus Greening Allen Morris Citrus greening or Huanglongbing (HLB) originated in China about 100 years ago. It is thought to be caused by the bacterium, Candidatus Liberibacter asiaticus. HLB has seriously affected citrus production in a number of countries in Asia, Africa, the Indian subcontinent and the Arabian Peninsula. Wherever the disease has appeared, citrus production has been compromised with the loss of millions of trees. It was first discovered in the state of Sao Paulo, Brazil in 2004 and Florida in 2005, two regions that account for almost 90 percent of world orange juice production. It is spread by a tiny insect called the Asian citrus psyllid when it feeds on the leaves of infected trees. Symptoms are leaves with a yellow/green blotchy mottled color and fruit that is lopsided, has aborted seeds, fails to color properly, and is bitter and small. It first reduces fruit yields, then kills the tree. A tree can be infected for up to two years and not show symptoms, yet still spread the disease. By February of 2008, less than three years after the first positive HLB test on a Florida citrus tree, near Homestead, the disease had spread to all 32 of Florida s commercial citrus producing counties. The Florida citrus industry, federal and Florida state government have invested approximately $70 million in over 100 research projects to find a cure for HLB. But a cure has not yet been found. Botchy Mottled Leaves Psyllid Lopsided Small Bitter Fruit with Aborted Seeds 1

2 Management Practices to Control HLB From an economic viewpoint, the main consequences of greening are increased tree mortality, reduced fruit yields, and increased costs of production. The recommended horticultural management practices to help control HLB are to scout for trees with infected leaves, remove those trees as soon as they are found, and aggressively spray to control psyllid populations. Most well-trained scouts can be 95% accurate in visually identifying HLB. About 10% of the infected leaves found in scouting are sent for polymerase chain reaction (PCR) testing in a lab as a check on the accuracy of the scouts. U.S. Sugar Corporation in Clewiston and the University of Florida Institute of Food and Agricultural Sciences Research Center in Immokalee operate PCR labs used by Florida growers. Scouting for HLB Uncontrolled HLB spreads at a non-linear rate, often doubling, tripling or more each year (Exhibit 1). The goal is, through controlling psylid populations and removing infected trees, to keep HLB infection at 2% or less. Unofficial estimates indicate that has been achieved on less than 100,000 acres of Florida s 524,640 acres of commercial citrus groves. Once the HLB infection rate exceeds 7-8% in a grove or block, the disease is usually uncontrollable. A particularly disturbing aspect of HLB is that psyllids prefer to feed on newly flushing leaves. Since multiple flushes throughout the year are more prevalent on young 1-4 year old trees, it is difficult to reset trees lost to HLB or other causes, or to replant individual blocks in a grove with high inoculum levels, and get the newly-planted trees to survive. Of particular concern is the impact of HLB on organic citrus production. Since organic growers can t effectively spray to control psyllid populations, organic production is impacted much more by greening than fruit produced in non-organic groves. Consequently, production of organic citrus is expected to decline much faster than production of conventional citrus, with prices for the increasingly scarce organic citrus products high and rising. In the 2003/04 season, the year before HLB was found in Florida, 242 million 90-pound boxes of oranges were produced on 564,844 bearing acres containing 75.4 million bearing trees (Exhibit 2

3 2). 1 By the 2007/08 season, 170 million boxes were produced on 464,000 bearing acres containing 61.7 million bearing orange trees. While part of that decline was the result of trees removed to control the spread of HLB, and an unprecedented high-priced Florida real estate market that diverted citrus groves to real estate development, most was due to the federallymandated citrus canker eradication program. The experiences with this program affected the success the Florida citrus industry has had in managing HLB. Citrus canker is a bacterial disease that causes lesions on leaves, stems and fruit, making the fruit, which is safe to eat, too unsightly to be sold. It is spread primarily by wind-driven rain and human contact. While it does not kill trees, if uncontrolled, it will eventually render trees unproductive. If controlled by management practices, it reduces fruit yields by 5 15%, and increases production costs, both from reduced yields and increased spraying needed to keep trees producing marketable fruit. The citrus canker eradication program legally required the destruction of all citrus trees in a 1900 foot radius of an infected tree, which is about 260 acres. After hurricanes spread canker throughout Florida in 2004 and 2005, the eradication program was deemed unsuccessful and discontinued. Consequently, the Florida citrus industry is managing canker and dealing with the resulting reduced fruit yields and higher costs. Between 1995 and 2006, 10 percent of Florida s citrus acreage (87,000 acres) was destroyed as part of the canker eradication effort, at a direct cost of $1.3 billion. Citrus Canker After the failed canker eradication program, many Florida growers felt that eradication of canker should never have been the goal, that managing and living with canker the way Brazilian growers had been doing for decades should have been the goal, and that the eradication program had destroyed tens of thousands of acres of citrus unnecessarily. This hurt the credibility of the 1 In Florida, a box of oranges is a standard unit of measurement and weighs 90 pounds. It contains oranges and produces 6-7 gallons of juice. Citrus fruit is now handled in bulk bins and trailers, thus the term box is a statistical measure only. 3

4 scientists and state and federal agencies with growers and as a result, many didn t take the threat of greening seriously. Consequently, a number of growers either did not follow recommended practices to control greening at all, or although they sprayed to reduce psyllid populations, did not remove infected trees that were still economically viable, which exacerbated the spread of the disease. The unpopularity of the canker eradication program was one reason no attempt was put into place to legally require citrus growers to manage HLB. By the time growers realized how serious greening was and began to aggressively follow recommended HLB management practices it was too widespread to effectively control. The industry desperately needed a way to survive greening until a cure was found. HLB was discovered in Maury Boyd s 400 acre grove near Immokalee in the spring of 2006, only six months after it was first discovered in Florida. At that time, 40 percent of the trees in some of the blocks in his grove were already symptomatic for greening. Maury ignored the advice of scientists that he needed to remove his infected trees because the grove s profitability would have been substantially reduced. With Maury s permission, the Florida Department of Agriculture s Division of Plant Industry (DPI) used his grove to train scouts because the infection was so widespread there. Maury had been a citrus caretaker for many years and had a reputation for experimenting with innovative ways to improve citrus yields and lower production costs. Maury developed a mixture of foliar nutritional compounds and began using it on his grove. HLB infection spread to 100%, but his grove thrived. Maury conducted tours through his grove for hundreds of interested growers and scientists, from both Florida and Brazil. Some groups were so large they came in buses. By the 2008/09 season, production in his grove had increased to 585 boxes per acre, compared to a state average of 354 boxes per acre for that season and a 5- year state average (excluding freeze and hurricane years) of 359 boxes per acre. It appeared to most growers and some scientists that enhanced foliar nutrient programs might keep citrus trees economically productive until a cure for HLB was found. By 2010, informal surveys indicated that about 75% of the growers in Florida had abandoned tree removal and adopted some version of Maury s enhanced foliar nutrient program, which still required aggressive control of psyllids. The cost of Maury s enhanced foliar nutrient program, net of the scouting and tree removal costs it eliminates, and ground fertilizer costs it reduces, are an increase in production costs of $288 per acre, which is 16 percent of direct cultural costs. Scientists believe these programs work by feeding nutrients to the tree through its leaves, bypassing the compromised root system and blocked phloem of a tree infected with HLB. However, many scientists were concerned that in the absence of removing infected trees, with the resulting increased inoculum levels that would be in groves, if the enhanced foliar nutrient programs were not effective on a long-term basis, 4

5 Maury Boyd s grove, now 100% infected with HLB and using his enhanced foliar nutrient program An example of waiting too late to begin an HLB management program 5

6 infection rates would be too high to enable getting HLB under control and the groves would be lost. Thus, they were against abandoning removal of infected trees as part of an HLB management program. Some citrus growers with low HLB infection rates (typically less than 5% infection) agreed with the concerns of these scientists and continued to scout for and remove infected trees, but also used various enhanced foliar nutrient programs to strengthen trees that may be infected but were not yet symptomatic. Since 2004, the year before HLB was discovered in Florida, the costs for managing a Florida citrus grove have more than doubled, increasing from $920 to $2,049 per acre. While some of this increase in costs is due to higher prices for fertilizers and chemicals and costs for managing canker, the vast majority is from greening management practices. Adding harvest and haul costs, depending on fruit yields (which are lower than in previous years because of HLB), and interest on capital investment (or loans) including a return to land, the result is that break-even costs for producing juice oranges have doubled, going from about $.73 per pound solids prior to the discovery of HLB in Florida to $ Impact of HLB on Citrus Production in Florida Compared to Brazil In the fall of 2008, at industry request, The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) led a collaborative effort by UF/IFAS, DPI, and the USDA s National Agricultural Statistics Service Florida field office (NASS) to conduct a survey to determine the extent of HLB infection in Florida citrus groves. In 2009, it was decided to make this an annual survey in order to track changes in infection rates. U.S. Sugar Corporation also joined this survey, providing additional helpful data from their PCR lab. The survey showed that HLB infection rates increased from 1.6% in 2007/08 to 21.9% by 2010/11 (Exhibit 3). After 2011, not enough growers were scouting for infected trees to obtain a representative sample and the survey was discontinued. Exhibit 4 illustrates the way this incidence of infection looks on a map of Florida. It is estimated that by 2011, every commercial citrus grove in Florida was infected with greening, although infection rates varied from less than 3% to over 75%. FUNDECITRUS, a Brazilian research organization, also conducted an annual greening infection survey for Sao Paulo State, where most of Brazil s citrus is produced. In 2008, four years after greening was discovered in Brazil, infection was 0.6%. By 2011, it had increased to 3.8%, substantially lower than in Florida (Exhibit 3). It was estimated that in 2011, 53% of Brazil s citrus groves were infected with greening with infection rates ranging from less than 1% to 7%. 2 Pounds of solids are a measure of the soluble sugar solids in juice. Fruit and bulk juice bought and sold by processors is priced per pound of solids. One gallon of ready-to-serve orange juice such as consumers buy in a store, contains pounds of solids. Oranges generally produce from 6 to 7 pounds of solids per 90-pound field box. Over 95% of Florida s oranges are processed into juice. 6

7 As a result of these much lower HLB infection rates, and ability to move new plantings into greening-free regions, citrus production in Brazil has not been affected by HLB nearly as much as in Florida (Exhibits 2 and 5). While it appeared as if enhanced foliar nutrient programs were the much needed bridge to the discovery of a cure for HLB, in the 2012/13 season the Florida citrus industry was shocked as citrus trees dropped the most fruit on the ground in a non-freeze year ever recorded. The original Florida orange crop estimate of 154 million boxes by NASS in October of 2012 was subsequently reduced seven times in monthly forecasts until it reached million boxes at the end of the season. Reflecting the potential for increased fruit drop again, albeit not at the recordsetting rate of the previous season, the initial Florida orange crop estimate by NASS for the 2013/14 season was only 125 million boxes. In January the estimate was reduced to 115 million boxes, and to 110 million boxes in April as fruit once again dropped off trees at rates seldom seen before the prior season, other than after a tree-damaging freeze. If realized, this will be the smallest Florida orange crop in a non-freeze year since 1967/68 crop. However, most growers and processors expect this estimate to be reduced again before the end of the season in June, with a final orange crop of about 105 million boxes. It now appears as if the concerns of many scientists that enhanced foliar nutrient programs may not be effective on a sustainable basis were correct. The continued decline in Florida orange production since is largely due to HLB, and in recent years comes not only from tree losses, but also from greatly increased pre-harvest fruit drop and smaller fruit, both characteristics of greening. The concern and fear of most of the Florida citrus industry is that if fruit volumes continue to decline, there will not be enough fruit to support an economically viable infrastructure of citrus processing, fresh packing, fruit harvesting and hauling, and other sectors that are important to the functioning of the industry. More importantly, that this will result in the loss of a major part of the $8.9 billion Florida citrus industry and the 76,000 jobs it supports. There are two key reasons why Brazil s citrus industry has not been impacted by HLB as much as Florida s. First, Brazilian growers, without the stigma of a recently failed disease management policy that Florida growers had experienced, took the threat of HLB much more seriously after it was first discovered than Florida growers. Thus, they were more aggressive in implementing effective greening management practices during the critical early stages after it was first detected when infection rates were low. Also, it is required by law in Brazil to scout for, locate and remove greening-infected trees, but as explained earlier, not in Florida. Second, Brazilian citrus production is moving further southward and northward ( running from greening ) as growers replant in areas such as Baru and Istapetininga where there are currently no psyllids and no disease pressures from greening. These new groves are also planted at higher 7

8 tree densities, and a larger percent are irrigated than the groves in the traditional production regions of Matao, Limieria, Araraquara, and Piriciaba. Thus, yields per acre will be much greater in these new regions than they have ever been for groves in the traditional regions. Florida growers have no such places without psyllids or pressure from greening to move their citrus production. Discussions with Brazilian growers indicate the general expectation is that most of the fruit lost in the areas where greening is currently most widespread will be offset by new production in these other regions, a process that is already happening. HLB Research HLB research is focused into three broad areas, tree resistance, psyllid control and disease management strategies. Tree resistance research is mainly focused on ways to find or develop rootstocks and/or trees that will be immune or resistant to HLB, either through genetic engineering or trials with rootstocks that show promise for traits of HLB resistance. Psyllid research is focused on insecticidal control. The two HLB horticultural management strategies that show the most promise are organizing the state s groves into Citrus Health Management Areas (CHMAS), and replanting economically unviable groves using ultra-high density advanced production systems. No matter how effective tree removal and psyllid control are, if a neighboring grove is not effectively managing HLB, the efforts in both groves are substantially compromised. For large contiguous plantings under one management that is not a problem. But in areas consisting of numerous smaller groves (less than 1,000 acres each), it is. IFAS extension personnel are thus leading efforts to organize these smaller groves into larger 10,000 20,000 acre citrus health management areas (CHMAs). All growers in a CHMA operate their psyllid spray program on the same schedule. These larger areas also enable small growers that are in the CHMA to use aerial spraying, which reduces costs compared to ground spraying. The result is more effective psyllid control since the insects are not being chased into neighboring groves on a different spray schedule. Currently there are 48 CHMAS in Florida covering over 500,000 acres. Higher density plantings enable greater fruit production from 4-10 year old trees because of the greater number of trees per acre, which increases the present value of earnings over the life of the grove. 3 But higher density groves are more costly to plant than groves of traditional densities of 116 to 145 trees per acre. Before HLB, most growers were unwilling to invest the additional funds to plant ultra-high density groves so most Florida groves were planted at traditional densities. In fact, after higher density groves are 10 years old, some anecdotal evidence indicates that the higher density crowds the trees and actually leads to reduced grove yields. 3 Citrus trees are four years old before they produce a commercially harvestable crop, and their production increases until they are about 12 years old, when production levels out. A citrus tree will produce fruit for over 30 years if it does not succumb to diseases or a freeze. 8

9 With endemic HLB, in order to offset increased tree attrition and increase the productive life of future groves potentially infected with HLB, some Florida citrus growers are considering replanting groves lost due to HLB or some other cause to densities ranging from 198 to 350 trees per acre. Some smaller groves producing fruit for the fresh market are being planted at densities as high as 570 trees per acre. In addition to providing more trees per acre to offset higher tree mortality from HLB, a key advantage of higher density groves is that when trees are lost, the neighboring trees grow to fill the empty spaces, thus helping further mitigate lost yields per acre. An advanced production system (APS) is being used where the higher planting density is combined with nutrients and water, precisely managed through a drip irrigation system. To reduce the impact of crowding as the trees mature, dwarfing rootstocks are used in APS groves. The smaller trees receive sunlight in their interior more uniformly than traditional trees, which improves fruit yields. Fruit harvesting costs are also reduced because the trees do not grow tall enough to require ladders. Economic analysis conducted by Morris and Muraro at the University of Florida showed that the economic life of a mature citrus grove planted at traditional densities is less than 8 years after it becomes infected with HLB if the infection is not controlled to less than 3%. That same mature grove planted at 270 trees per acre has an economic life of 15 years or more. However, young (less than 5 year old) trees are at greater risk of greening infection than mature trees because of the increased attraction of psyllids to the multiple leaf flushes of young trees. Thus, the challenge for replanting an unprofitable citrus grove at higher densities in order to increase its economic life is to prevent or minimize greening infection in young trees so they live long enough to become profitable. That has been the main impediment to replanting economically unproductive citrus groves in Florida since the discovery of greening. Prior to the discovery of HLB in Florida, when annual tree losses were 2-4% and lost trees could be easily replaced by resetting, groves had an economic life of over 25 years if not destroyed by a freeze. Some groves were still in production after 80 years. The Future Lakeland Ledger, January 27, In the darkest hours of Florida's eight-year battle against citrus greening, Congress has come through with its most substantial commitment yet a guaranteed $125 million over five years to finance research against the ruinous bacterial disease. The money is part of a bipartisan new Farm Bill congressional leaders announced late Monday. The research money caps a four-year effort by U.S. Sen. Bill Nelson, D-Florida, to create a longterm funding solution to attack greening, arguably the biggest threat to Florida's $9 billion citrus industry in generations. It comes on top of $20 million for greening-related research in the recently approved federal budget that was obtained by Nelson; U.S. Rep. Tom Rooney, R-Okeechobee, whose district includes Polk County; and other Florida representatives. 9

10 Will researchers discover a cure in time to save the Florida citrus industry; and when or if they do discover a cure, will the weak and declining U.S. orange juice market 4 support high enough prices for growers to take the risks and commit the capital to replant the 400,000+ acres of infected groves? Exhibit 1. Spread of HLB Infection in Groves Where It Is Unmanaged Note: The above line graphs are for both uncontrolled and controlled HLB. They are based on actual data. The large differences, such as the projection for 45 years to spread to 100% in Brazil on one graph and only about 3 years on another, are due to differences in the mix of controlled and uncontrolled HLB, different tree ages, different levels of inoculum in surrounding groves, and different fruit varieties. Exhibit 1 was reproduced with permission from Tim Gottwald, USDA, ARS. 4 The U.S. orange juice market has declined 41% since While some of this decline is due to higher orange juice prices, demand analysis indicates that over half of it is not price-related. Orange juice demand is declining, as evidenced by declining penetration (fewer households buying orange juice) and increasing impacts of substitutes, mostly juice blends and juice drinks. 10

11 Exhibit 2. Florida Orange Production, Acres and Trees Season Thousand Million Million Boxes Bearing Acres Bearing Trees 2000/ / / / /05 (a) /06 (a) /07 (a) / / / / / / /14 E (a) Effects of hurricanes, the canker eradication program and the start of HLB Note: Production year is November - June Source: USDA, National Agricultural Statistics Service, Florida Field Office 11

12 Exhibit 3 12

13 Exhibit 4 13

14 Exhibit 5. Orange Production in Sao Paulo, Brazil Season Million Boxes 2000/ / / / / / / / / / / / / / /15E 320 Note: Production year is May - January Source: USDA, Foreign Agricultural Service 14