Shot Hole Disease

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.

​

Cherry leaves infected with shot hole disease (Kate Russell)

Shot hole, or Coryneum blight, is a fungal disease of stone fruits, such as almonds, apricots, nectarines, peaches, plums, and prunes.


Symptoms of shot hole disease

Spring is when shot hole 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 the damaged tissue falls off, leaving the signature BB hole.


As the fungus spreads, more leaf tissue is damaged until the leaf falls. Significant infections can reduce photosynthesis, 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, avoid overhead watering. Remove any infected buds, leaves, fruit, and twigs and throw them in the trash. In the fall, apply fixed copper or Bordeaux mixture treatments. Bordeaux mixture is one part copper sulfate, one part slaked lime, and ten parts water. This mixture can injure leaves, so it is applied when trees are bare. It can also leave a blueish-green stain on walkways, fences, and buildings, so use it cautiously. You can buy ready-made Bordeaux mixes, but it tends to stick to leaves better when fresh. Total coverage is essential for either of these treatments to be effective.