Apricot (Prunus armeniaca) trees are hardy in Zones 5 to 7, but are susceptible to bud damage and fruit loss if early spring temperatures drop below freezing. Plant them in full sun and fertile, well-drained soil. Apricot trees naturally grow 20 to 40 feet tall, depending on the variety, but they are generally kept at 10 to 12 feet tall in home landscapes or orchards.
Apricot trees are susceptible to two species of Valsa fungi that cause cankers on limbs and trunks of affected trees. The cankers are oval areas of dead bark that get larger each year and are surrounded by a roll of callus tissue – healthy tissue produced by the tree to contain the infection. Valsa fungi enter apricot trees through wounds caused by insects, pruning or mechanical damage.
Reduce damage to trees to prevent infection. Remove debris from around trees, prune diseased limbs, and destroy to prevent the spread of infection. A fungicidal spray approved for Valsa cankers on apricot trees can be applied according to the manufacturer’s directions to help control the diseases.
A soil-borne fungus that infects the roots of apricot trees causes verticillium wilt. The disease causes dull colored foliage and leaf drop. The wood under the bark of infected branches is streaked gray and brown. One section or the whole tree may be affected.
No effective control exists for verticillium wilt and the fungus can live in the soil for several years. Remove and destroy infected apricot trees. Do not plant apricot or other susceptible trees in the same area.
Bacterial spot caused by Xanthomanas pruni, and shot hole disease caused by Pseudomonas syringae, cause similar symptoms on apricot trees. Water-soaked spots appear on the underside of infected leaves. After the spots turn brown or black, the centers fall out, leaving a reddish-colored margin. Individual leaves with many spots may yellow and drop prematurely. Small cankers that release spores appear on the twigs in spring.
High nitrogen fertilizer increases the susceptibility of apricot trees to leaf diseases. Do not plant new trees near infected trees. There is no effective treatment for bacterial spot or shot hole disease, although a Bordeaux mixture of fungicide applied at the rate recommended by the manufacturer may help control the disease.