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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production
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Permanent Link: http://ufdc.ufl.edu/IR00001941/00001
 Material Information
Title: Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production
Physical Description: Fact Sheet
Creator: Brown, Mark
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
Publication Date: 2002
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Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status: Published
General Note: "Published January 2002."
General Note: "FE 330"
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Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00001941:00001

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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production1 Mark Brown and Ed Stover2 1. This is EDIS document FE 330, a publication of the Department of Food and Resource Economics, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL. Published January 2002. Please visit the EDIS website at http://edis.ifas.ufl.edu 2. Mark Brown, research economist, Florida Department of Citrus, University of Florida, Gainesville, FL; and Ed Stover, assistant professor, Indian River Research and Education Center, Fort Pierce, FL, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean. Introduction Quick decline strains of the citrus tristeza virus (CTV) and the brown citrus aphid, which is an efficient vector in spreading this disease, are widespread in Florida. There is a strong possibility that this situation may result in a sharp increase in citrus tree losses in the near future. Because trees on sour orange rootstock are vulnerable to CTV, there is the potential of CTV killing most of the trees on this rootstock. Based on data from the Bureau of Citrus Budwood Registration and a survey of grapefruit in the Indian River region, an estimated 14 percent of the orange trees (about 12 million trees) and an estimated 42 percent of the grapefruit trees (about 5.3 million trees) were on sour orange rootstock in 2000. Since most of the trees on sour orange rootstock were planted before 1990, the surviving trees on the rootstock are now in the most productive stage of their lives. Therefore, the loss of these trees to CTV could have a significant impact on total citrus production. Assumptions in Economic Projections Rate of Loss Scenarios Three scenarios were used to project acreage losses to CTV. In the first scenario, nearly all acreage of trees on sour orange rootstock will be lost during the next eight years; in the second scenario, the acreage will be lost during the next 12 years; and in the third scenario, acreage will be lost over the next 16 years. Research in other citrus growing regions suggest that CTV may spread faster to orange trees than to grapefruit trees, with an expected tree loss to CTV over the next eight years for orange trees and 12 years for grapefruit trees. As a result, these time frames are used for the primary scenarios in the analyses described in this report. Assumptions on CTV Incidence Based on industry observation of CTV symptoms in the field, the initial incidence of CTV was assumed to be highest in the south and west and lowest in the north and central regions. The Indian River region was assumed to have a somewhat higher but relatively low incidence. In addition, other factors

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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production 2 besides CTV were expected to result in acreage losses. Non-CTV acreage-loss rates were assumed based on historical loss rates implied by the commercial tree census. Assumptions on Production Future orange and grapefruit production trends were estimated by applying average historical yields per acre to projected acres. It should be noted that actual production levels in any given season could deviate substantially from these trends based on environmental factors that influence yield. Since historical yield records were based on groves using a high proportion of sour orange rootstock, the accuracy of projections will be influenced by the relative productivity of groves on replacement rootstocks. Production estimates for oranges and grapefruit were made based on different planting assumptions. It was assumed that planting levels for oranges in the upcoming seasons will equal the 1997-1999 average level and that the grapefruit planting levels will be at replacement levels (i.e., acres lost are replanted). Deviations from these assumptions could markedly influence actual citrus production levels. Production Projections Production Reductions Assuming that CTV losses occur over the next eight years, it is estimated that potential orange production will decrease from 237 million boxes in 2001 to 227 million boxes in 2004; afterwards, production should increase, reaching 250 million boxes in 2010 (Table 1). This set of estimates suggests that CTV could reduce potential orange production by 15 million boxes. (If CTV losses occur over the next 12 years, the low point in orange production is estimated to occur in 2005 at 233 million boxes. If CTV losses occur over the next 16 years, the low point is estimated to occur in 2005 through 2007 at 240 million boxes.) It is estimated that potential grapefruit production will decrease from 47 million boxes in 2001 to 36 million boxes in 2005; afterwards, production should increase, reaching 48 million boxes in 2010, assuming that CTV losses occur over the next 12 years (Table 2). This set of estimates suggests that CTV could reduce potential grapefruit production by four million boxes in 2001 and three million boxes in 2010. (If CTV losses occur over the next eight years, the low point in grapefruit production is estimated to occur in 2003 and 2004 at 34 million boxes. If CTV losses occur over the next 16 years, the low point is estimated in 2006 at 38 million boxes.) Orange Production Estimates by Variety Based on CTV losses occur over the next eight years, potential early and midseason orange production is projected to decrease from 135 million boxes in 2001 to 126 million boxes in 2004, and then increase to 132 million boxes by 2010 (Table 3). Potential late orange production is projected to increase from 102 million boxes to 118 million boxes over the 10-year projection period, with a slight decrease in production early in that period. In 2001, early/midseason oranges and late oranges are estimated to account for 57 percent and 43 percent, respectively, of round-orange production; by 2010, these shares are estimated to change to 53 percent for early and midseason oranges and 47 percent for late oranges. Grapefruit Production Estimates by Variety Based on CTV losses occurring over the next 12 years and replacement planting levels, potential white seedless grapefruit production is projected to decrease from 18 million boxes in 2001 to 13 million boxes in 2005, and then increase to 19 million boxes in 2010 (Table 3). Potential red seedless grapefruit production is projected to decrease from 29 million boxes in 2001 to 23 million boxes per year from 2004 through 2005, and then increase to 29 million boxes in 2010. Grapefruit production projections for the Indian River and Interior regions are provided in Table 4. Conclusion Over the next 10 years, CTV could have a significant impact on Florida citrus production. Both orange and grapefruit production could decline over

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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production 3 the next several years, depending on the incidence of CTV. The extent that orange and grapefruit production might decline depends on the rate at which CTV spreads. In other words, if CTV spreads more slowly, the decreases in production will be smaller and will occur farther in the future.

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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production 4 Table 1. Orange production estimates.a Season Without Additional Losses Due to Tristeza With Tristeza Losses Occuring Over Next 8 Years With Tristeza Losses Occurring Over Next 12 Years With Tristeza Losses Occurring Over Next 16 Years Production Acre Loss Rateb Production Acre Loss Rateb Production Acre Loss Rateb Production Acre Loss Rateb million boxes %million boxes %million boxes %million boxes % 2001-022522.3 2375.4 2443.9 2463.4 2002-032562.4 2315.7 2414.6 2463.8 2003-042602.4 2275.0 2375.0 2444.2 2004-052642.5 2273.9 2344.8 2424.5 2005-062682.6 2302.9 2334.1 2404.4 2006-072722.6 2342.5 2353.3 2404.0 2007-082742.7 2382.5 2382.8 2403.5 2008-092782.7 2432.6 2422.6 2433.1 2009-102802.7 2462.6 2462.6 2462.8 2010-11 282 2.8 250 2.7 249 2.7 249 2.7 a Average yields and average plantings assumed. b Loss rate due to normal attrition and CTV. Table 2. Grapefruit production estimates.a Season Without Additional Losses Due to Tristeza With Tristeza Losses Occurring Over Next 8 Years With Tristeza Losses Occurring Over Next 12 Years With Tristeza Losses Occurring Over Next 16 Years Production Acre Loss Rateb Production Acre Loss Rateb Production Acre Loss Rateb Production Acre Loss Rateb million boxes %million boxes %million boxes %million boxes % 2001-02512.4 4410.4 476.4 495.1 2002-03512.5 3813.3 448.4 466.2 2003-04512.5 3411.0 409.9 447.3 2004-05512.5 345.5 379.6 418.2 2005-06512.6 372.3 367.0 398.1 2006-07512.6 411.7 384.0 386.8 2007-08512.6 441.8 402.3 394.9 2008-09512.6 471.9 441.9 413.2 2009-10512.7 482.0 461.9 432.3 2010-11 51 2.7 50 2.1 48 2.0 46 2.1

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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production 5 Table 2. Grapefruit production estimates.a Season Without Additional Losses Due to Tristeza With Tristeza Losses Occurring Over Next 8 Years With Tristeza Losses Occurring Over Next 12 Years With Tristeza Losses Occurring Over Next 16 Years Production Acre Loss Rateb Production Acre Loss Rateb Production Acre Loss Rateb Production Acre Loss Rateb million boxes %million boxes %million boxes %million boxes % a Average yields and average plantings assumed. b Loss rate due to normal attrition and CTV. Table 3. Estimated round-orange and grapefruit production by variety. Season Orangesa Grapefruitb Early and Midseason Late Total White Seedlessc Red and Pink Seedless Total million boxes 2001-02135 102 237 18 29 47 2002-03131 100 231 17 27 44 2003-04127 100 227 15 25 40 2004-05126 101 227 14 23 37 2005-06127 103 230 13 23 36 2006-07128 106 234 14 24 38 2007-08129 109 238 15 25 40 2008-09130 113 243 17 27 44 2009-10131 115 246 18 28 46 2010-11 132 118 250 19 29 48 a Assumes average yields, average plantings, and CTV losses occurring over eight years. b Assumes average yields, replacement plantings, and CTV losses occurring over 12 years. Non-CTV loss rates for white seedless grapefruit were assumed to be higher than those for red seedless grapefruit, based on 1998-2000 loss rates; over the projection period, non-CTV loss rates for white (red) seedless grapefruit averaged about 3.4% (2.0%); weighted average non-CTV loss rates for white and red seedless grapefruit are shown in Table 2, the no CTV scenario. c Includes seedy grapefruit. Table 4. Indian River versus Interior estimated grapefruit production, with tristeza losses occurring over next 12 years.a Season Indian River Interior Whiteb Red Total Whiteb Red Total million boxes 2001-0211.2 17.9 29.1 7.2 11.1 18.3 2002-03 9.9 16.4 26.3 6.7 10.9 17.6

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Projecting Effects of Citrus Tristeza Virus on Florida Citrus Production 6 Table 4. Indian River versus Interior estimated grapefruit production, with tristeza losses occurring over next 12 years.a Season Indian River Interior Whiteb Red Total Whiteb Red Total million boxes 2003-04 8.7 14.5 23.2 6.4 10.6 17.0 2004-05 7.6 13.1 20.7 6.2 10.3 16.5 2005-06 7.4 12.5 19.9 6.1 10.1 16.2 2006-07 8.0 13.2 21.2 6.2 10.1 16.3 2007-08 9.2 14.5 23.7 6.3 10.4 16.7 2008-0910.4 16.0 26.4 6.5 10.6 17.1 2009-1011.4 17.2 28.6 6.7 10.7 17.4 2010-11 12.1 18.1 30.2 6.8 10.9 17.7 a Assumes average yields and replacement plantings. Non-CTV loss rates for white seedless grapefruit were assumed to be higher than those for red seedless grapefruit, based on 1998-2000 loss rates; over the projection period, non-CTV loss rates for white (red) seedless grapefruit averaged about 3.4% (2.0%); weighted average non-CTV loss rates for white and red seedless grapefruit are shown in Table 2, the no CTV scenario. b Includes seedy grapefruit