The symptoms are a sprinkling of brown dots on new leaves, later becoming translucent flecks, and finally becoming brown dead areas which grow and distort the leaves. Eventually the growth buds die. Browning and dead areas develop on the flowers at or near the base of the petals. Boron can build up in potted plants from frequent fertilization. Symptoms of boron toxicity are yellowing of leaf tips, followed by marginal chlorosis and premature leaf drop.
Prevention consists of using fertilizer low in boron.
Treatment includes pruning off the affected parts, and irrigating with a solution of copper sulfate and limewater. Copper This may occur in plants potted in a medium low in copper, such as a mixture of sphagnum moss and peat. The first symptoms are marginal chlorosis of a few leaves at the tips of the main shoots, followed by brown dead spots. If the deficiency is not corrected, the leaves are severely restricted in size, and leaf drop and dieback of shoots occur. The table of contents of the Compendium is at azalea problem reference .