Flowering dogwood (Cornus florida) is a relatively small flowering tree that is popular in Maryland home landscapes. Although it is a native species, it is susceptible to several diseases, pests, and abiotic (nonliving) problems that can reduce the quality of flowering and overall growth. Selecting disease-resistant cultivars and using good growing practices will reduce the chances of these problems.
Use this picture guide (or the text table below) to identify the most common problems of flowering dogwoods and related Cornus species.
Dogwood trees are known for their beautiful spring blooms in shades of white, pink and red. However, you may notice the leaves on your dogwood tree turning red earlier than they should in the summer or fall.
Red leaves on a dogwood are usually a sign of an underlying disease, pest infestation or environmental stress factor impacting the tree. While it may not kill the dogwood immediately, it weakens the plant and ruins its ornamental value. Therefore, it’s crucial to diagnose and treat the cause of the red leaves quickly to save your dogwood tree.
In this article, we’ll explore the three most common reasons for red dogwood foliage and solutions for fixing the problems
Anthracnose Disease
The leading cause of premature red dogwood leaves is anthracnose, a fungal disease that thrives in cool, wet weather conditions. It spreads rapidly via water and is highly contagious to other dogwood trees nearby.
The first signs of anthracnose are small, reddish or purple blotches forming on the leaf edges. Soon the leaves shrivel up and drop off the branches. The flowers and fruits can also become infected and drop early. Without treatment, the disease moves from the lower branches to the upper branches, eventually defoliating the entire tree.
Treating Anthracnose
Start treatment at the first sign of infection Here are a few effective solutions
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Remove and destroy affected leaves to prevent spread.
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Apply a copper-based fungicide like Bonide Copper Fungicide before leaves emerge in early spring.
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Make a baking soda spray (4 tsp baking soda, 2 tsp oil, 2 tsp liquid soap per 4 liters water) and spray the dogwood weekly.
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Improve air circulation and light penetration by pruning dense growth.
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Water at the base, not from above, and allow time for leaves to fully dry.
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Choose anthracnose-resistant varieties like Celestial, Ruth Ellen or Stellar Pink.
Dogwood Borer Infestation
Dogwood borers are moth larvae that feed on the bark and burrow into the trunks, causing premature red leaves. Heavy infestations can kill young trees within a couple seasons.
Look for small holes in the bark with sawdust-like “frass” around them. As the vascular tissues are damaged, leaves start dropping. Eventually the bark peels off as well.
Treating Borer Infestations
Catching borers early is key. Effective remedies include:
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Spraying insecticide like Monterey Garden Insect Spray on trunks to kill larvae.
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Making a homemade insecticidal soap spray to suffocate borers.
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Applying neem oil or horticultural oil sprays to deter egg-laying.
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Removing severely infested branches before spread.
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Avoiding pruning when borers are active in spring/summer.
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Clearing weeds/mulching to eliminate hiding spots.
Dogwood Leaf Scorch
Leaf scorch leads to red, browned leaves with distorted shapes. It’s caused by drought stress, which dogwoods are prone to due to shallow roots.
While not fatal, leaf scorch weakens trees and makes them more vulnerable to deadlier problems. Affected leaves may cling on until fall or drop prematurely.
Fixing Leaf Scorch
Revive moisture-stressed trees by:
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Deep watering 2-3 times per week in droughts/heat waves.
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Applying mulch to prevent evaporation and cool roots.
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Checking soil moisture before watering with a meter.
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Pruning the canopy to improve internal air circulation.
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Planting in part shade locations away from hot afternoon sun.
When to Call an Arborist
If more than 50% of the foliage is damaged or major limbs are dying off, contact a professional arborist. They have specialized tools and treatments to diagnose and manage severe dogwood tree issues.
Catching problems early before widespread damage gives the best chance of saving your ornamental dogwood tree. At the first signs of unusual red leaves, take prompt action using the solutions outlined. With proper care, your dogwood will continue thriving and blooming for years to come.
Dogwood Sawfly Dogwood sawfly larvae are covered with a white powder which may mimic bird-droppings. Photo: Bruce Watt, University of Maine, Bugwood.org Dogwood sawfly larvae in two different stages. Mature dogwood sawfly. Photo: Bruce Watt, University of Maine, Bugwood.org
- Symptoms: leaves are chewed or eaten entirely.
- The dogwood sawfly is an occasional pest of dogwoods. They are mostly seen on shrub dogwoods – e.g., silky dogwood (Cornus amomum) and red osier dogwood (C. sericea).
- The larvae (juveniles) resemble caterpillars and feed on the foliage.
- Adult sawflies, which resemble tiny wasps, emerge during late spring and early summer.
- The female lays eggs on the undersides of the leaves.
- Upon hatching, the young larvae feed together and chew the leaves.
- After the second molt, the larvae become covered with a white powdery material.
- After their final molt, they lose the powdery covering and change color. The mature larvae are yellowish with a shiny black head and black spots.
- These mature larvae will wander about in search of an overwintering site, generally in soft or decaying wood.
- There is one generation each year. Monitor for them starting in early July.
- Management is seldom needed, but if desired, wear gloves and manually remove and discard the larvae.
- If an infestation is heavy, particularly on a young plant, the larvae may be sprayed with horticultural oil registered for landscape use. Apply according to the label instructions.
Leaf and Flower Petal Blight Leaf and flower blight (Botrytis sp.) on flowering dogwood. Photo: Penn State Department of Plant Pathology & Environmental Microbiology Archives, Penn State University, Bugwood.org
- Symptoms: spotting on the flower bracts to complete collapse of the bracts; gray, fuzzy growth on terminal leaves and flowers.
- This is caused by a fungus, Botrytis cinerea, commonly called “gray mold.”
- Infected bracts that fall onto leaves can also cause leaf and twig infections.
- This disease can be serious during wet spring weather.
- Generally, no chemical controls are needed for this disease because drier weather will stop disease progression before serious damage occurs.
5 Favorite Flowering Dogwood Trees | NatureHills.com
FAQ
What are the signs of dogwood stress?
Stress. The decline of dogwoods may also be contributed to a combination of these two major issues, which causes stress to the trees. Stressed trees may exhibit smaller-than-normal leaves and have wilting leaves, pale-green leaves, early fall coloration, and an overall poor appearance.
Can a dogwood recover from leaf scorch?
Once leaf scorch has occurred, there is no cure. The dehydrated portions of the leaf will not turn green again, but with proper water management, the plant may recover. Prevention of scorch needs to begin with winter watering.
How to get rid of red dogwood?
The most effective way to kill dogwood trees is via cut-stem treatment. You will directly cut the tree down to the stem and apply a professional herbicide. Our recommendation is Triclopyr 4, as it has been shown to be very effective against brush and shrubbery and is labeled for treating dogwood.