Copper deficiency or "wither tip" has become more common in Washington apple and pear orchards. About mid-June, terminal leaves on part or most of the tree turn yellow, wither and fall. Bark may be cracked and rough.
Postharvest foliar applications of 1 pound of copper per acre as copper sulfate or basic copper sulfate will usually correct the symptoms. If symptoms are severe, mid-season sprays of copper chelate or basic copper sulfate products (bearing trees) or copper chelate, copper sulfate, or basic copper sulfate products (non-bearing trees) can be applied but may cause foliage and fruit injury.
Adding copper to zinc dormant sprays will not increase leaf copper levels.
Caution: All copper products are potentially phytotoxic. Applying copper sprays when fruit is present can cause severe fruit russetting, particularly on Anjou. If possible, delay applications until after harvest. Fruit injury sometimes can occur when foliar copper products are mixed with calcium chloride or applied within a week of calcium chloride sprays. Excessive copper application can increase soil copper to levels that are toxic to fruit trees.