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Citrus Greening Effects on Fruit Size Distribution in Citrus Trees

Citrus Greening Effects on Fruit Size Distribution in Citrus Trees. Chris Oswalt Extension Agent, Polk County & Tim Spann CREC, Lake Alfred. Introduction. Greening causes fruit to be small, misshapen, lopsided, develop an off flavor and abscise prematurely

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Citrus Greening Effects on Fruit Size Distribution in Citrus Trees

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  1. Citrus Greening Effects on Fruit Size Distribution in Citrus Trees Chris Oswalt Extension Agent, Polk County & Tim Spann CREC, Lake Alfred

  2. Introduction • Greening causes fruit to be small, misshapen, lopsided, develop an off flavor and abscise prematurely • Groves can become unproductive in as little as 2-4 years (Ke et al. 1988) • Yield can be reduced by 10 to 80% depending on percent of canopy affected (Bassanezi et al. 2006)

  3. Fruit Symptoms

  4. Introduction • Quantitative data about how yield is reduced is limited • Hypothesis: greening infected trees have a shift in fruit size distribution, being more heavily skewed toward smaller fruit, and that this may be a possible method for detecting greening infected blocks as well as for eliminating greening fruit from loads

  5. Experimental Site • 9-year-old ‘Valencia’ on carrizo • First greening find Dec. 2006 • 109 trees, removed immediately • Jan. 2007, second find • 102 trees, 100 removed in August 2007 • Jan. 2008, 74 trees with visible symptoms

  6. Healthy tree Greening tree found 1/08 Greening tree found 1/07

  7. Methods • Trees hand harvested April 9-11, 2008 • 5 healthy (symptomless) trees • 6 PCR+ • 2 trees from Jan. 2007 find • Fruit sized by hand based on fresh fruit size standards • <125, 125, 100, 80, and 64s • Fresh weight by size and total FW were recorded • 125 fruit were sorted into symptomatic and asymptomatic

  8. Results • Greening reduced total yield by ~25% (1 box) • 125 fruit on 1-year infected trees were 35% symptomatic

  9. Results • 50-60% of total yield was 125 or smaller fruit on infected trees compared to healthy trees

  10. Significance to Processors/Packers • Due to smaller fruit size total juice volume produced will be less from greening trees • Potential off-flavors in greening fruit • For fresh fruit ~5% of fruit is lost due to size (<125), another 10-15% is lost due to symptoms (poor fruit quality)

  11. Significance to Growers • In the block used in this study 15% of trees have been removed since first greening find • Direct loss of nearly 1500 boxes in 18 months • The 3 grove inspections to date have each found 4.5 – 6% infection

  12. Conclusions • For Valencias greening can be detected based on fruit size distribution • Data can be used to develop better economic models • Data indicate that processors and packers may be able to help ID unknown areas of greening

  13. Additional Research • Determine if these effects are the same for Hamlin and grapefruit • Determine yield loss due to premature fruit drop as well as from reduced fruit size

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