Oak Wilt and Dutch Elm Disease in Macomb County

Oak Wilt and Dutch Elm Disease (DED) are two of the most destructive tree diseases in Michigan, including Macomb County. Both move quickly, cause significant canopy dieback, and can kill mature, otherwise healthy shade trees in a short period of time. By the time homeowners notice early symptoms, the disease is already well-established within the trees vascular system.

As an ISA Certified Arborist with Owen Tree Service, I routinely inspect oaks and elms affected by these aggressive pathogens. While each disease is caused by a different fungus and spreads in different ways, they share one critical factor: Early preventive measures are essential to protect trees before infection occurs.

One of the most effective tools for preventive protection is macro-vascular injection (macro-infusion) of a fungicide into the tree trunk. This treatment delivers powerful fungicides directly into a trees vascular system, protecting uninfected trees from infection and helping maintain long-term tree health. It is important to understand that these injections cannot cure a tree that is already infected - they are strictly preventive.

OAK WILT: One of the Most Aggressive Oak Killers in Macomb County

Cause

Oak Wilt is caused by the fungus Bretziella fagacearum, which spreads through the trees’ vascular system, blocking water transport inside the tree. The disease is especially aggressive in trees in the red oak group, such as, black oaks, red oaks and pin oaks.

Severity

Trees in the red oak group can succumb to oak wilt in as little as 4 - 6 weeks after the initial infection, with the fungus rapidly halting water transport.

Symptoms include

• Leaf wilting and discoloration from the top down.

• Rapid canopy dieback.

• Premature leaf drop.

Trees in the white oak group, such as bur oak, white oak, swamp white oak and willow oak are less susceptible but can still die if the infection is severe.

Spread

Oak Wilt spreads via:

1. Sap beetles: These insects carry fungal spores to fresh pruning wounds or broken branches.

2. Underground root grafts: Oaks of the same species often form root connections, allowing the fungus to move between neighboring trees.

Preventive Measures

Macro-vascular injections are used in Macomb County to protect healthy, high-value oaks in areas with known oak wilt risk.

Key points to know:

• Fungicide injections do not cure infected trees.

• Injections are most effective when applied before the tree shows symptoms.

• Preventive injections create a chemical barrier that reduces the likelihood of the fungus establishing itself and moving within the tree.

For oak trees that are already infected, injections will not reverse the damage. In such cases, removal of the tree will probably be necessary to protect surrounding oaks.

DUTCH ELM DISEASE: A Historic and Ongoing Threat in Macomb County

Cause

Dutch Elm Disease (DED) is caused by fungi (Ophiostoma novo-ulmi and Ophiostoma ulmi) that attack a tree’s xylem, blocking water movement and causing rapid canopy decline.

Severity

DED progresses quickly in mature American elms. Infected trees often die within 1 - 2 years, sometimes faster, especially in areas with high bark beetle populations.

Spread

DED spreads through:

1. Bark beetles: Carry spores from infected trees to healthy ones, introducing the fungus under the bark.

2. Root grafts: Natural root connections allow the fungus to move underground from tree to tree.

Preventive Measures

Macro-vascular fungicide trunk injections can protect healthy elm trees.

Injections can only work on an infected tree if the fungus has not reached the main trunk. If the point of infection is on a branch 8-9’ from the main trunk, and the branch is removed, then it might be kept out of the main trunk.

Trees in areas with active bark beetles or prior DED cases benefit most from preventive injections. This would, essentially, be any elm tree in Michigan.

A single fungicide trunk injection can safeguard high-value elm trees, allowing them to resist infection for up to three years.

Trees showing advanced symptoms - wilting branches, flagging, or streaked vascular tissue are typically beyond treatment. In those cases, removing the tree is the best way to prevent spreading the disease to any nearby trees.

Why Early Detection and Prevention Are Critical

Both oak wilt and Dutch elm disease are fast-moving and potentially lethal.

Without preventive action:

• One infected tree can threaten entire neighborhoods or groves of trees.

• Infected trees act as a source of inoculum for nearby healthy trees.

• Once visible symptoms appear, options are extremely limited.

Macro-vascular fungicide injections are an essential tool for protecting uninfected trees, but they must be part of a broader preventive management plan that includes:

• Proper sanitation and pruning practices.

• Avoiding open wounds during high-risk periods.

• Monitoring for early signs of disease.

• Strategic spacing and root-graft management.

Owen Tree Service: Preventive Protection for Macomb County Trees

At Owen Tree Service, our ISA Certified Arborists and Certified Technician's provide:

• Preventive macro-vascular injections for high-value oaks and elms.

• Disease diagnosis and early risk assessment.

• Education on pruning schedules and seasonal precautions.

• Monitoring and follow-up protection plans.

Our goal is to protect healthy oak and elm trees before infection occurs, minimizing loss and safeguarding Macomb County’s urban and suburban landscapes.

Key Takeaways

 1. Oak wilt and Dutch elm disease are aggressive, fast-moving diseases.

 2. Macro-vascular injections protect healthy trees but cannot cure infected ones.

 3. Early preventive action is the only reliable method to maintain tree health.

 4. Proper timing, diagnosis, and professional expertise are essential for effective protection and is available with the ISA Certified Arborists at Owen Tree Service.

 5. Trees showing advanced symptoms require assessment for removal to prevent spreading the disease to neighboring trees.

 By understanding these deadly tree diseases, and taking preventive action, Macomb County homeowners can preserve the health, beauty, and value of their mature oaks and elms for years to come.