Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 8, 1998
Publication Date: N/A
Interpretive Summary: Nutritional differences between blight-affected and healthy trees have been reported, but they were based on one-year observations and often from widely separated areas. Long-term intensive observation of three blocks of trees on the same blight-susceptible rootstocks backed by diagnostic tests provided the basis for this report. By sampling only healthy trees, the leaf levels reflect differences in nutrient uptake between the three blocks that seem to predispose the trees to developing blight. The lower Ca and higher S levels are probably responsible for the reported lower internal pH of healthy trees.
Of three adjacent blocks of orange trees (Citrus sinensis L. Osbeck) on rough lemon rootstock (C. limon S. Burm.f.), one was essentially citrus blight-free, and two were strongly affected. The three blocks were fertilized equally and irrigated from the same water source. The blight free Grove 1 was planted on undisturbed soil, and Groves 2 and 3 were planted on filled-in land; Grove 2 was heavily limed in 1970 before planting. Annual analysis of leaves collected from healthy trees in July from 1986 to 1997 for 14 elements showed that the blight free Grove 1 had lower leaf Ca and higher S, Zn, and Mn than the two blight affected Groves 2 and 3. The leaves in Grove 2 had higher N, K, Na, Cl, and B concentrations than in Grove 3; P and Mg were lower. There were no significant differences in Ca, S, and the metal ions.