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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
Citrus Greening Effects on Fruit Size Distribution in Citrus Trees

Chris Oswalt

Extension Agent, Polk County

&

Tim Spann

CREC, Lake Alfred

introduction
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)
introduction4
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
experimental site
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
slide6

Healthy tree

Greening tree found 1/08

Greening tree found 1/07

methods
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
results
Results
  • Greening reduced total yield by ~25% (1 box)
  • 125 fruit on 1-year infected trees were 35% symptomatic
results9
Results
  • 50-60% of total yield was 125 or smaller fruit on infected trees compared to healthy trees
significance to processors packers
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)
significance to growers
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
conclusions
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
additional research
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