Invasive Pests in the Midwest: What to Watch For and How Arborists Respond

June 13, 2025

Protect Your Trees Year-Round

Invasive tree pests pose a serious threat to the health, stability, and lifespan of the trees on your property. In the Midwest, these pests are not just a seasonal nuisance—they are a year-round concern that can lead to widespread damage if left unchecked. At Midwest Tree Surgeons, we specialize in identifying, treating, and preventing infestations before they become costly problems.


If you are a homeowner, land manager, or property developer in this region, understanding which pests are active—and how professional arborists respond—can help you take informed steps to protect your investment.

A group of trees are standing in the water.

Why Invasive Pests Are a Serious Problem

Unlike native insects that have natural predators and balanced populations, invasive pests are non-native species that often spread rapidly and cause severe damage because local ecosystems lack the means to control them. These pests can:


  • Compromise tree health
  • Spread diseases
  • Cause structural instability
  • Lead to premature tree removal
  • Impact surrounding plant life and biodiversity



Their impact is not always immediate. Some infestations progress silently, causing internal decay or weakening branches before visible signs appear.

A close up of a tree branch with white flowers.

Common Invasive Pests in the Midwest

1. Emerald Ash Borer

Originally from Asia, the emerald ash borer is one of the most destructive pests in North America. It targets all species of ash trees, boring into the trunk and cutting off the tree’s ability to transport water and nutrients.


Warning Signs:

  • Canopy thinning
  • D-shaped exit holes in bark
  • Bark splitting
  • Increased woodpecker activity


Without treatment, infested trees typically die within 2–4 years.

A tree with lots of pink flowers on it

2. Asian Longhorned Beetle

This beetle targets a wide range of hardwoods including maple, elm, willow, and poplar. The larvae tunnel deep into the wood, compromising structural integrity.


Warning Signs:

  • Round exit holes
  • Frass (sawdust-like material) at the base of the tree
  • Dieback in the canopy
  • Oozing sap from the trunk



This pest has the potential to devastate urban and rural forests alike.

oak leaves

3. Gypsy Moth (Spongy Moth)

While native to Europe and Asia, this pest has spread throughout the eastern and Midwestern United States. The larvae feed on the leaves of over 300 species of trees, including oak, birch, and aspen.


Warning Signs:

  • Defoliation during spring and summer
  • Egg masses on trunks or outdoor structures
  • Caterpillars crawling on trunks and sidewalks



Repeated defoliation weakens trees and makes them vulnerable to secondary diseases.

A close up of a dogwood tree with white flowers and green centers.

4. Scale Insects

Scale insects affect a wide variety of tree species. They latch onto branches and stems, sucking out sap and weakening the host.


Warning Signs:

  • Sticky residue (honeydew) on leaves or nearby surfaces
  • Yellowing leaves
  • Sooty mold development
  • Visible bumps along branches and twigs



Scales are often overlooked because of their size but can spread rapidly and silently.

How Arborists Respond

At Midwest Tree Surgeons, we take a science-based approach to pest management, combining thorough diagnostics with targeted interventions.


1. Tree Health Assessments

Early detection is key. Certified arborists perform in-depth evaluations of canopy condition, bark texture, and insect activity. We often identify problems before a homeowner notices symptoms.


2. Preventive Treatments

For known threats like EAB, systemic insecticide treatments can be applied before infestation begins. Preventive care is especially important for high-value trees or trees in stressed environments.


3. Targeted Removal

In cases of severe infestation or irreversible damage, strategic removal may be necessary to prevent spread to surrounding trees.

4. Integrated Pest Management (IPM)

We use an IPM approach that combines cultural, biological, and chemical methods. This includes promoting tree health through proper pruning and soil care, encouraging beneficial insect predators, and using treatments only when needed.


5. Monitoring and Follow-Up

Ongoing care is essential. We work with property owners to monitor previously treated trees, track pest activity, and adjust strategies seasonally.


Stay Ahead of the Threat

Invasive pests are not going away. In fact, climate variability and international trade continue to introduce new threats to Midwest landscapes. Proactive care is not optional—it is the most cost-effective and environmentally responsible way to protect your trees.



If you suspect your trees are under attack or want to safeguard them before problems arise, Midwest Tree Surgeons is here to help. Our certified arborists are trained to identify, manage, and prevent infestations with precision and care.

A person is holding a red maple leaf in their hand.
an oak tree
An orange bird perched on a tree branch with green leaves
asian long horned beetle
cypress tree
The sun is shining through the branches of a cherry blossom tree.

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September 29, 2026
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Evergreens are often valued because they provide year-round color, screening, and structure in the landscape. When sections of an arborvitae, juniper, spruce, or similar evergreen suddenly begin turning brown or losing foliage, however, bagworms may be responsible. Bagworms are caterpillars that construct protective bags from silk and pieces of the plants they are feeding on. Because those bags blend into surrounding foliage, an infestation can become significant before the insects attract much attention. Understanding how bagworms feed and when they are easiest to control can help protect valuable trees and shrubs from unnecessary damage. The Bags Can Be Easy to Miss Bagworms get their name from the portable cases they build around themselves. As the larvae feed , they add pieces of needles, leaves, and twigs to the outside of the bag. This camouflage can make them difficult to recognize, particularly when populations are still relatively small. The bags may look like small brown cones or pieces of dried vegetation hanging from the branches. Penn State Extension notes that bagworms can become serious pests on arborvitae, juniper, spruce, fir, and other conifers because substantial feeding damage can occur before the infestation becomes obvious.

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Why Correct Pest Identification Matters Before Treatment

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When insects begin damaging a tree, the first instinct may be to treat the problem as quickly as possible. But not every insect requires the same response, and some insects that look harmful may not be the actual cause of the decline. Applying the wrong treatment can waste time, money, and potentially put additional stress on the tree.  Midwest Tree Surgeons takes a diagnosis-first approach to tree care. Correct pest identification helps determine whether treatment is needed, which method is appropriate, and whether the real problem may involve disease, environmental stress, or another underlying issue.
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