Shot hole disease can attack several types of fruit trees, but apricot is especially vulnerable. This fungal infection, previously called Coryneum blight, favours wet conditions, especially in the spring.
Plant Parts: Leaves, shoots, buds and fruit.
Season: At the end of Spring - Summer
Symptoms: Leaf symptoms first appear as reddish spots that enlarge until the centre of the spot becomes a tan colour and the centre of the spot will eventually fall out producing a hole. Infected buds will turn black and fruit will have similar coloured lesions to the leaves.
Severe infections will cause the leaves to drop early, sometimes as early as in the spring. Extensive infection also begins to affect the fruit as it develops, causing scabby, rough spots that are concentrated on the top of the fruit and that may flake off and leave rough patches behind.
Control: Removal of the infected leaves and some of the infected twigs will help in controlling the fungus. A preventative fungal regime is recommended - A spray of copper oxychloride at bud swell will help.
Prevention: Shothole fungus overwinters on buds and twigs that are infected. The spores on these parts of the tree can be transferred during winter and spring rains and when water splashes up from the ground.
The best way to treat this is to apply an appropriate fungicide during the dormant season. This can help to minimize or prevent the disease from infecting healthy plant material in the spring and during the rainy and wet season. This can be done just after the leaves fall or right before buds break in the spring. You should also prune off and destroy diseased branches or twigs and dispose of this material away from the tree to keep from spreading spores accidentally. Check out the Care instructions in the annual winter pruning section.
References: Gardening Know How, Whitney Cranshaw, Colorado State University, Bugwood, and FST team.
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