Tropical Fruit Tree Diseases

Overview

Tropical fruit trees are sun-loving trees that prefer warm climates and high humidity. Most tropical fruit trees are deciduous, produce blooms, and lie dormant during the winter. Though most tropical fruit trees are hardy, many can be susceptible to disease, some of which are curable.

Powdery Mildew

Powdery mildew is a fungal disease that initially attacks the leaves of the fruit tree. The disease appears as a chalky, white coating on the surface of the leaves. The leaves may also curl. As the disease spreads, the mildew will continue onto the stems, flowers and fruit of the tree. While younger tropical fruit trees are most susceptible to powdery mildew, all ages can be affected. If the disease is left untreated, the tree's foliage will begin to dry, brown and yellow. The flowers will begin to distort and will appear disfigured and decayed. Powdery mildew is a common disease to all plants and trees. Though the disease normally does not cause death, a severely infected fruit tree will produce unusable fruit, if any at all.

Anthracnose

Anthracnose, or leaf blight, is a spore spread, fungal disease that is common throughout the Eastern U.S. This disease attacks the leaves of the tree, causing black blotches and dead areas on the leaves. Leaf blight does not affect all tropical trees in the same manner. While some tropical trees will only have their leaves affected, other tropical trees can see severe twig, shoot, bud and fruit damage. The disease causes trees to defoliate, resulting in a weakened tree that can become more susceptible to other diseases.

Verticillium Wilt

Verticillium wilt is a soil-borne fungal disease that attacks the tree through its root system. Most trees do not show signs of infection until the tree is severely affected. The signs include slow growth, yellow leaves, leaf browning, and dieback of shoots and branches. Wilting usually occurs suddenly and is accompanied by drying, defoliation and leaf curling. The toxins of the fungus attack the inner tissues of the tree, leaving it permanently affected. Fungicide treatments will not cure this disease. Remove and destroy the tree. Avoid replanting in the area, as the new plant or tree will also be affected.

Papaya Ringspot Virus

The papaya ringspot virus is an aphid-spread disease that attacks only papaya tropical trees. This disease causes the appearance of dark green, sunken rings on the fruit of the tree. Severely infected trees produce smaller leaves and the tree's growth will become stunted. Though younger trees are most susceptible, mature trees can be affected. Young, infected trees are generally robbed of their fruit production ability. Managing the disease is possible but somewhat difficult. It involves a combination of treatments and practices. See your nursery or horticulturalist for assistance.

Black Rot

Black rot is a fungal disease that prefers warm, humid areas. This disease normally settles into the tree in the late fall and winter months. The tree will begin to show signs of infection during early spring when its growing season begins. Signs of infection include spotted leaves, fruit rot, and limb cankers. Leaves will initially show small purplish specks that will slowly enlarge into circular lesions. Infected fruit initially shows reddish spots that turn purple and then black, as aging occurs. Lesions and cankers will appear on the bark, branches and stems of the tree. Black rot can be removed with diligent pruning of the infected areas and fungicide treatments.