The first colonists who came to Massachusetts brought with them bags of apple seeds to start orchards. Today apple orchards are common across the country. But apple trees are not without problems. Common problems afflicting apples include fungus and insects. Although preventative care such as planting disease-resistant varieties and routine spraying can help, the process is not foolproof. When your apple trees are struck by pests or disease, diagnosing the problem is the first step to treating it.
Contact your local garden center or extension service to find out which pests or diseases are most common in your area.
Examine the tree's bark for signs of infestation such as holes, eggs, loose bark or tunnels. Eggs indicate gypsy moths, which will cause the leaves of the tree to fall off. Small holes and tunnels in the bark may be left by boring insects such as termites or beetles, while large holes are made by woodpeckers seeking insects. Most boring insects infest a tree that is already unhealthy. If you have these insects, your tree may be under stress already due to drought, poor nutrition, high winds or improper pruning.
Inspect apple blossoms during the flowering season. If the buds are chewed on or completely eaten, weevils may be the culprit. Blossoms that wither and die may indicate fire blight. Shoots infected with fire blight turn a scorched brown or black, and spongy reddish lesions appear on the bark. On warm days these lesions may ooze orange-brown liquid, and the tree's leaves will pucker and turn yellow.
Take a close look at the foliage. Leaves falling off may be a sign of scale, which also can cause the small twigs near the ends of branches to die back. Pale yellow spots on leaves are a sign of cedar apple rust. If the leaves have a gray, moldy appearance, you may be dealing with powdery mildew. Mites leave stippled yellow leaves with white dots. If the leaves are cracked and distorted, with olive green spots on the underside, the culprit may be leaf scab.
Pick an apple, cut it in half and examine it. Apples with worm-like creatures inside may be under attack by apple maggots. If the apple's skin has black spots on it, the tree may be a victim of black rot. Coddling moths leave tunnels inside apples, while the plum circulio beetle leaves cuts on the outer skin. Apples under attack by the plum circulio beetle fall from the tree too early.
Take a photo of your tree's symptoms and return to the garden center or extension office to confirm your diagnosis.