Does it look like someone attacked your tree with a shotgun? Are leaves pelleted with BB-sized holes? If so, your tree may have shot hole disease.
Shot hole disease, also known as Coryneum blight, is a fungal disease that commonly affects peach, nectarine, apricot, plum, almond and prune trees. This is no surprise because all of those trees are in the stone fruit (Prunus) family.
Symptoms of shot hole disease
Shot hole disease normally appears in spring, as fungi attack new growth. The damage first looks like small (1/10-1/4”) reddish or purplish-brown spots. There may be a light green or yellow ring around the holes. These spots get a little bigger, dry up and damaged tissue falls away, leaving the signature BB hole. As the fungus spreads, more leaf tissue is damaged until the leaf falls. Significant infections can reduce the amount of photosynthesis that can occur, weakening the plant and decreasing fruit production. The fungi can also affect the fruit, leaving toughened spots on the skin. Branches may develop concentric lesions when infected.
Preventing shot hole disease
Since the fungi thrive in wet conditions, overhead watering should be avoided where the disease has occurred before. Remove any infected buds, leaves, fruit and twigs and throw them in the trash. In fall, fixed copper or Bordeaux mixture can be applied. Bordeaux mixture is 1 part copper sulfate, 1 part slaked lime and 10 parts water. This mixture can injure leaves, so it should only be used when trees are bare. It can also leave a blueish-green stain on walkways, fences and buildings, so use it with care. You can buy ready-made Bordeaux mixes, but it tends to stick to leaves better when it is fresh. Total coverage is needed for either of these treatments to be effective.
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