Oklahoma’s fluctuating climate — humid summers, cold winters, and frequent storms — creates ideal conditions for a range of fungal and bacterial tree diseases. Early identification is key to preventing irreversible damage.
At Mercer Tree Service, our certified arborists in Edmond, OK diagnose and treat tree diseases using industry-proven methods to restore tree health and prevent spread.
1. Oak Wilt
Trees Affected: Red Oaks, Shumard Oaks, Blackjack Oaks
Cause: Fungal pathogen Bretziella fagacearum
Symptoms:
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Rapid leaf wilting and browning, typically starting at the top of the canopy
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Premature leaf drop during summer
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Brown discoloration in the outer sapwood
Treatment & Prevention:
Oak Wilt spreads through root grafts and beetle activity. Infected red oaks typically cannot be saved, but early intervention can contain the spread. Preventive measures include:
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Pruning only in late fall or winter (when beetles are inactive)
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Applying fungicide injections to protect high-value trees
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Removing and properly disposing of infected material
2. Hypoxylon Canker
Trees Affected: Oak, Sycamore, Maple, Pecan
Cause: Stress-induced fungal infection (Biscogniauxia atropunctata)
Symptoms:
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Grayish bark patches that flake away
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Rapid canopy dieback starting from the top
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Decaying wood beneath the bark
Treatment & Prevention:
There is no direct cure for Hypoxylon Canker. The best defense is maintaining vigorous tree health through regular watering, nutrient support, and pruning. Prevent soil compaction and avoid mechanical injury to the trunk.
3. Cedar-Apple Rust
Trees Affected: Eastern Red Cedar, Apple, Crabapple, Hawthorn
Cause: Fungal spores that alternate between cedar and apple hosts
Symptoms:
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Orange, jelly-like galls on cedar twigs
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Yellow-orange leaf spots on apples and crabapples
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Premature leaf drop and fruit blemishes
Treatment & Prevention:
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Prune and dispose of cedar galls before spring spore release
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Apply fungicide sprays early in the growing season
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Choose rust-resistant apple and crabapple cultivars for new plantings
4. Fire Blight
Trees Affected: Pear, Apple, Crabapple
Cause: Bacterium Erwinia amylovora
Symptoms:
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Blackened, “burned” leaf tips and blossoms
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Shepherd’s crook shape at the ends of shoots
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Bacterial ooze on branches during humid conditions
Treatment & Prevention:
Fire Blight spreads rapidly during warm, wet weather. Control involves:
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Pruning infected shoots at least 12 inches below visible symptoms
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Sterilizing tools between cuts
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Applying bactericide treatments in spring
5. Anthracnose
Trees Affected: Sycamore, Ash, Elm, Maple, Oak
Cause: Fungal pathogens that thrive in cool, wet spring weather
Symptoms:
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Irregular brown spots or blotches on leaves
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Twigs and new shoots die back
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Premature leaf drop
Treatment & Prevention:
Anthracnose is rarely fatal but can weaken trees over time. Treatments include:
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Sanitation: Remove and dispose of infected leaves each fall
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Pruning: Improve air circulation through structural pruning
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Fungicide applications: Protect new growth during wet seasons
6. Bacterial Leaf Scorch
Trees Affected: Elm, Oak, Sycamore, Maple
Cause: Bacterium Xylella fastidiosa spread by leafhoppers
Symptoms:
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Marginal leaf browning (scorch) that starts mid-summer
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Progressive canopy thinning each year
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No recovery in affected limbs
Treatment & Prevention:
While there is no cure, soil injections and PHC programs can slow progression and improve vigor. Regular watering, mulching, and nutrient management reduce stress, helping trees resist infection.
Protecting Your Trees with PHC (Plant Health Care)
Most Oklahoma tree diseases are opportunistic — they take hold when trees are already stressed. Proactive care through a Plant Health Care (PHC) plan keeps trees healthy enough to resist pathogens. Mercer Tree Service offers:
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Soil nutrient analysis and deep-root fertilization
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Growth regulators to balance canopy and root development
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Targeted fungicide and bactericide treatments
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Certified arborist monitoring for early disease detection
Work with a Certified Arborist in Edmond, OK
If you suspect your tree may be diseased, early professional diagnosis is essential. At Mercer Tree Service, our certified arborists combine field experience with modern treatment techniques to protect trees across Edmond, Oklahoma City, and surrounding areas.
Schedule a tree health inspection today and keep your trees strong, safe, and disease-free.
