Apple Diseases in West Virginia

Fungal Root Diseases

• Apples in West Virginia are susceptible to several fungal diseases, although some cultivars have resistance to particular fungi. Many fungal diseases can be prevented with a regular spray program that includes fungicide treatments. Some of these fungi attack roots and can cause significant damage and even death. Black root rot is a fungus that produces black, finger-like fruiting bodies near the root zone, and the roots themselves are covered in a black sheath of fungus. White root rot fungus covers the roots in a cream colored layer. Phytophthora is a fungus that affects the roots and root collar around the tree. Trees die as the fungi infect the cambium layer, restricting or preventing nutrient and water transport throughout the tree.

Fungal Fruit and Leaf Diseases

• The damage to fruits and leaves from fungi can range from cosmetic to severe. Apple scab produces round, corky lesions that render the fruit unattractive, but just as edible as before. Cedar apple rust infects apples from other host plants, such as juniper. Symptoms include lesions on both fruits and leaves, often accompanied with tiny black spots. The trees may be weakened, but the fungal infections are seldom fatal. Powdery mildew covers leaves in a white, felty substance and may produce corky areas on the fruits. These diseases are not fatal, but can be prevented with a regular fungicide regimen.

Nutrient-Related Diseases

• Apple trees in West Virginia may experience diseases as a result of a deficiency in nutrients. These symptoms can often mimic fungal diseases. Cork-like areas are often present on fruits when there is a deficiency in calcium or boron. Leaves that are yellowish with deeper green veins may indicate insufficient iron or manganese. Zinc deficiency can cause leaves to be smaller than normal, and copper deficiency causes leaves on the ends of branches to yellow and die, while a shortage of magnesium causes the edges of leaves to turn yellow.

Environmental Diseases

• Disease or disease-like symptoms can appear as the result of the environmental conditions in West Virginia to which the tree is exposed. Russetting, or rough, brown areas on the fruit surface, are often caused by wet conditions during the first six weeks after the tree blooms. The fruit is still consumable. If the roots have been under water for any length of time due to flooding or over-irrigation, the trees may be deprived of oxygen and not able to absorb minerals, which will cause the leaves to yellow and the tree to eventually die, mimicking phytophthora. Drought may cause leaves to yellow and fall, premature ripening of the fruit, and scorching of leaves.

Other Diseases

• Other diseases that may affect apples in West Virginia are fire blight and apple mosaic virus. Fire blight is a bacterial infection that kills blossoms, shoots, limbs, and sometimes whole trees. The disease produces cankers and withering branch tips. Apple Mosaic virus forms yellow blotches on that which may become necrotic. The tree is weakened and may produce fewer apples; however, the apples are generally in good condition.