Symptoms
Symptoms begin with yellowing in intercostal areas at the base of leaflets or leaf margin. The chlorosis expand to the whole leaf as the deficiency continues. The margin often remains green.
Eventually necrotic patches appear in the yellow areas which terminate as intercostal leaf scorch.
Symptoms are most severe in the oldest leaves, which have green veins and large areas of marginal and intercostal necrosis.
Reasons
Magnesium deficiency.
Manganese deficiency is similar, but here intercostal yellowing starts on younger leaves.