Magnesium deficiency is noticeable by interveinal chlorosis starting from older leaves and progressing upward to new leaves with persisting deficiency.
Chronic magnesium deficiency is best treated with soil applications of magnesium fertilizers or dolomite. Apply magnesium sprays only when moderate or severe deficiency symptoms appear suddenly or are not controlled by soil applications of magnesium. To avoid creating other nutient imbalances, magnesium deficiency should be confirmed before applying sprays. Two sprays are required. Apply the first during June and the second about 4 or 5 weeks later. Apply as a separate spray. Trees with little or no fruit need not be sprayed as the deficiency is severe only on trees with heavy crops of fruit.