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Citrus Greening Effects on Starch Content and Nutrient Balance of Citrus Leaves

Citrus Greening Effects on Starch Content and Nutrient Balance of Citrus Leaves. Tim Spann, Arnold Schumann, Ed Etxeberria, Ron Brlansky CREC, Lake Alfred. Introduction. Blotchy mottle symptom of greening resembles nutrient deficiencies

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Citrus Greening Effects on Starch Content and Nutrient Balance of Citrus Leaves

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  1. Citrus Greening Effects on Starch Content and Nutrient Balance of Citrus Leaves Tim Spann, Arnold Schumann, Ed Etxeberria, Ron Brlansky CREC, Lake Alfred

  2. Introduction • Blotchy mottle symptom of greening resembles nutrient deficiencies • Zn, Mn, Fe and other deficiencies commonly appear on trees with greening symptoms

  3. Objectives • Determine the nutritional status of leaves with different symptoms on greening symptomatic tree and compare these with control leaves from healthy trees • Determine if there are changes in leaf nutrients that can be used as early indicators of greening infection • Determine how foliar application of nutrients affects greening symptoms

  4. 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

  5. Methods • Branch study • 22 trees with greening symptoms and 15 “healthy” trees were selected • All “healthy” trees were PCR – • 19 of the 22 symptomatic trees returned a PCR value • Treatments were applied on Feb. 29

  6. Treatments • 9 treatments, 5 reps on greening and healthy trees • Grower’s fertilizer 4B shot bag (0.06 Fe, 4.34 Mg, 1.0 Mn, 0.93 Zn) applied at recommended 2 gal / acre • FeSO4, MgSO4, MnSO4, ZnSO4 • K-Phite 7LP (phosphorous acid) • KeyPlex (Mg, S, B, Fe, Mn, Mo, Zn) • SAver (2-0-10) • Water + adjuvant control • All treatments applied with hand pump up sprayer to run off

  7. Data Collected • Each limb was documented photographically • Leaf samples • pre-treatment, 2 WAT, and 6 WAT • nutritional analysis (P, K, Mg, Ca, S, Zn, Mn, Fe, Cu), PCR, starch and ash content • greening tree samples were taken for each symptom on that tree (yellow veins and blotchy mottle) • Sampled leaves were also documented photographically

  8. Results Narrative • Starch was significantly higher (3-4x) in leaves of HLB infected trees compared to healthy trees • P, Ca, S, Zn, Mn, Fe, and Cu were all significantly lower in HLB leaves • K was significantly higher in HLB leaves • Mg was unaffected by HLB • N, B not analyzed

  9. Results Narrative • Mn was the only element affected by treatments • Both MnSO4 and shot bag significantly increased Mn in control trees – HLB trees were unresponsive • Visually, no change in symptoms were detected

  10. Conclusions • There are significant changes in quantities and ratios of certain nutrients in greening trees as well as accumulation of large quantities of starch • Changes may be detectable in parts of the tree where PCR cannot detect bacterium • Changes may occur prior to the development of visual symptoms • More data is needed to validate these results and determine if these changes are unique to greening

  11. Next Steps • More data is needed to validate these results and determine if these changes are unique to greening • Treatments need to be applied at other times of year when better uptake can be achieved • Longer term studies need to be conducted • Higher, remedial rates of nutrients need to be applied, not just label recommended maintenance rates

  12. Take Home Message • Better plant nutrition will not cure greening, but it’s not going to hurt and it just may help slow the disease progression in a tree

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