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

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

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 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

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

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 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

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 –FeSO 4, MgSO 4, MnSO 4, ZnSO 4 –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 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 –FeSO 4, MgSO 4, MnSO 4, ZnSO 4 –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

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 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

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 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

Results Narrative Mn was the only element affected by treatments –Both MnSO 4 and shot bag significantly increased Mn in control trees – HLB trees were unresponsive Visually, no change in symptoms were detected Mn was the only element affected by treatments –Both MnSO 4 and shot bag significantly increased Mn in control trees – HLB trees were unresponsive Visually, no change in symptoms were detected

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 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

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 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

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 treeBetter 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