The dogwood tree is commonly grown for ornamental purposes, often as a standalone tree. It is popular for its exotic, bright-colored flowers. Some dogwood varieties grow red berries during the early winter season. Dogwoods are low-maintenance trees but they are susceptible to some garden diseases. Early detection and disease management can help you to save your dogwoods from many deadly infections.
The anthracnose disease affects flowering varieties of dogwoods like the Pacific dogwood. Anthracnose disease spreads very quickly and it is critical to identify it during its nascent stage. It is caused by the Discula fungus. This disease propagates quickly in cool, slightly wet conditions that are associated with the late spring and fall season. Dogwoods exposed to extreme weather variations like extended dry spells or freezing winters become more vulnerable to anthracnose disease.
The symptoms first develop in the dogwood tree’s leaves. Initial indications include tan spotting along the upper portion of the leaves. Some spots may have a purple-colored rim to them. Some leaves could develop necrosis with a weathered look to the outer edges. A blight-like pattern develops on the stem during the late spring or the early fall season. The blight spots have a girdle-like shape. The spots are commonly found among the leaf nodes. Such blighted twigs develop a typical, bent appearance.
Mulching dogwoods is vital, particularly during the winters. Dogwoods exposed to alternative freezing and thawing patterns are more prone to fungal infections. You should apply a 3-inch thick mulch around your dogwood before the winter season sets in. You shouldn't water the mulch repeatedly, i.e. keep it moistened but not wet and replace it every 3 weeks. Avoid irrigating the dogwoods with overhead irrigation. This system of spraying water creates extremely moist conditions in the upper part of the tree’s foliage. Such conditions are a thriving ground for fungal infections. You can also use organic fungicides. Spray the fungicide at regular intervals, with a minimum gap of 12 days.
Dogwood Canker Diseases
Cankers are essentially dead spots on a tree wherein the plant’s nutrition supply has been stopped. Dogwood cankers are commonly found on the main trunk area. A particular kind of canker disease called the Diffuse Canker is typical to dogwoods. It is caused by the canker fungus that spreads inside the bark, sucking-away the bark’s nutrition. The most serious but rare, Trunk Canker among dogwoods is caused by the Phytophthora fungus.
Most cankers are first found among the lower, slightly older branches. Once canker infection seeps into the bark, small callus-like formation is found on the main bark.
Short dry spells can stimulate canker infection. You should maintain proper soil moisture, particularly among young dogwoods. Hindered root development, often caused due to nearby structures can cause root suffocation. This too makes the tree susceptible to fungal infections. Older branches are more prone to canker infections. Ensure that you regularly prune-off dying and bent branches. Branches that are intensely twined around the main bark should be immediately pruned.
Leaf Spot Disease
Leaf spotting is common among dogwoods. If it isn't detected early, spotting can spread to the dogwood fruit. It can cause widespread infection among the berries. This form of berry-spreading leaf spotting is caused by the Septoria fungus. Sometimes, it is difficult to determine the cause of leaf spots among dogwoods. It is often caused by other factors like soil nutrition deficiency. However, the fungal or Septoria spotting is more common in humid conditions.
Leaf Spot Identification
The symptoms include characteristic purple-colored spots on the leaves. The spots are often oval shaped. The spots may develop a grayish hue in their center during wet conditions. The purple border among leaf spots is the identifying mark of spotting caused by fungal infections. The duller, dark brown-colored spots could be caused by soil nutrition deficiency.
Leaf Spot Treatment
Nutrition-based spotting can be treated by enriching the soil bed with basic, NPK fertilizers and regular watering. However, fungal spotting needs systematic care. You should regularly prune the dogwood trees, using lightweight shears. This helps to minimize injury to the plant that is common during pruning sessions. Fungal leaf spot infections are known to spread quickly through injured sites on the tree. Spotting often initiates in damp soil conditions. Ensure that the soil bed is not waterlogged. You should use organic mulch made from pine bark to increase the water-draining capacity of the soil.