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Technical Resources-Forest Health

Healthy Trees Vibrant Neighborhood Forests!

A new 2016 study reports that imported forest pests cause $2 billion in damages each year and the U.S. property owners and municipalities pay most of the bill (Treebune News May 16, 2016). Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yrs. (Ecological Applications). The notable insect and disease devastation to our municipal areas have been Dutch elm disease or the most recent Emerald Ash Borer.

Our goal as municipal forest managers and caretaker of our communities trees is to be alert. Try to observe the health and condition of your trees and neighborhood forests just like you would a family member. Federal Governmental agencies are always monitoring for new and emerging insect and disease issues. These may end up on the “Watch For” list because of the potential problems they can create for the health of the overall forest. Taking care of our forest resources is everyone's responsibility.

When managing tree resources it is important to know your tree species since some insect and diseases are species specific while others are more general and attack many species of trees. Insects and diseases (I&D) is a part of the forest ecosystem. Some insects and diseases occur under certain conditions and have a short term impact on the tree. Anthracnose is one such disease. Only with repeated incidents can it eventually impact the tree. Others such as Emerald ash borer or sudden oak death syndrome lead to a much faster decline.

Through out time there have always been periods of insect or disease epidemics such as Dutch elm disease or Emerald Ash Borer. with the help of state and federal governmental agencies who monitoring forest health we can identify and address potential problems that could create forest health issues.

As a state and a nation we have lost species diversity which can lead to economic losses. We are faced with climate changes that could impact our forests health in the long run.

However, most importantly in an urban environment these insects and diseases can cause weaknesses in the tree that can cause branch breakage and risk. Because of this forest health monitoring is an important part of a municipal forestry program and a homeowner’s regular yard care routine. Proper urban and community forest management leads to Healthy Trees Healthy Communities and Healthy Citizens! Maintaining a healthy forest also reduces liability and risk for our citizens.

Healthy Urban and Community Forests Healthy Statewide Forests! Stay current on forest health issues in Illinois and the Midwest through the 2015 Illinois Forest Health Highlights and the 2015 Forest Health Watch. These documents tell you what insect and disease problems have occurred in the past year.

There are five sections below: 1) Watch List - Under Federal Quarantine; 2) Insects and Diseases Currently of Concern to Illinois Forestry; 3. Watch for: Insects and Diseases with the Potential to Impact Illinois; 4. Diagnosing Tree Health and 5) New Research on Forest Health related topics.

1. Watch List - Under Federal Quarantine - The watch list shows targeted pests that have federal quarantines in certain areas of this state. Note: Other Federal and State quarantines may apply.

In addition to federal quarantines, state-level quarantines might apply.
Learn about state-level quarantines.


Emerald Ash Borer: Attacks Ash trees (Fraxinus species) Green ash and White ash are preferred also white fringe trees (in the same family as ash).


Asian Longhorned Beetle:

Attacks Maples, Willows, London planetrees, Elm, Mountain Ash, Polar, Birch, Elm Boxelder, Buckeye, Horse chestnut, and Katsura most preferred. It was found in NE Illinois and has been declared eradicated.

  • USDA Aphis

    • Healthy Trees Vibrant Neighborhood Forests!

    A new 2016 study reports that imported forest pests cause $2 billion in damages each year and the U.S. property owners and municipalities pay most of the bill (Treebune News May 16, 2016). Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yrs. (Ecological Applications). The notable insect and disease devastation to our municipal areas have been Dutch elm disease or the most recent Emerald Ash Borer.

    Our goal as municipal forest managers and caretaker of our communities trees is to be alert. Try to observe the health and condition of your trees and neighborhood forests just like you would a family member. Federal Governmental agencies are always monitoring for new and emerging insect and disease issues. These may end up on the “Watch For” list because of the potential problems they can create for the health of the overall forest. Taking care of our forest resources is everyone's responsibility.

    When managing tree resources it is important to know your tree species since some insect and diseases are species specific while others are more general and attack many species of trees. Insects and diseases (I&D) is a part of the forest ecosystem. Some insects and diseases occur under certain conditions and have a short term impact on the tree. Anthracnose is one such disease. Only with repeated incidents can it eventually impact the tree. Others such as Emerald ash borer or sudden oak death syndrome lead to a much faster decline.

    Through out time there have always been periods of insect or disease epidemics such as Dutch elm disease or Emerald Ash Borer. with the help of state and federal governmental agencies who monitoring forest health we can identify and address potential problems that could create forest health issues.

    As a state and a nation we have lost species diversity which can lead to economic losses. We are faced with climate changes that could impact our forests health in the long run.

    However, most importantly in an urban environment these insects and diseases can cause weaknesses in the tree that can cause branch breakage and risk. Because of this forest health monitoring is an important part of a municipal forestry program and a homeowner’s regular yard care routine. Proper urban and community forest management leads to Healthy Trees Healthy Communities and Healthy Citizens! Maintaining a healthy forest also reduces liability and risk for our citizens.

    Healthy Urban and Community Forests Healthy Statewide Forests! Stay current on forest health issues in Illinois and the Midwest through the 2015 Illinois Forest Health Highlights and the 2015 Forest Health Watch. These documents tell you what insect and disease problems have occurred in the past year.

    There are five sections below: 1) Watch List - Under Federal Quarantine; 2) Insects and Diseases Currently of Concern to Illinois Forestry; 3. Watch for: Insects and Diseases with the Potential to Impact Illinois; 4. Diagnosing Tree Health and 5) New Research on Forest Health related topics.

Watch List - Under Federal Quarantine

The watch list shows targeted pests that have federal quarantines in certain areas of this state. Note: Other Federal and State quarantines may apply.

In addition to federal quarantines, state-level quarantines might apply. Learn about state-level quarantines.


Emerald Ash Borer: Attacks Ash trees (Fraxinus species) Green ash and White ash are preferred also white fringe trees (in the same family as ash).


Asian Longhorned Beetle:

Attacks Maples, Willows, London planetrees, Elm, Mountain Ash, Polar, Birch, Elm Boxelder, Buckeye, Horse chestnut, and Katsura most preferred. It was found in NE Illinois and has been declared eradicated.

Sudden Oak Death:

Attacks: broad range of hardwoods, softwoods, landscape and herbaceous plants

European Gypsy Moth:

Attacks more than 300 species of trees and shrubs including fruit trees, oak, aspen, birch, cedar, cottonwood, larch, poplar and willow.

Light Brown Apple Moth: Attacks more than 2,000 species of plants and trees and 250 agricultural crops.

Spotted Lanternfly:

Attacks fruit crops and trees

Thousand Canker Disease:

This is a fungal disease transmitted by the tiny Walnut Twig Beetle.

Attacks all walnuts with the Eastern Black walnut being the most susceptible and the rare butternut.

Common Shoot Beetle (quarantine recently extended to Illinois)

Insects and Diseases Currently of Concern to Illinois Forestry.

MAJOR THREATS IN ILLINOIS:Bacterial Leaf Scorch (10 Illinois counties have this in southern and central Illinois)

Gypsy Moth

: Attacks oak, apple, alder, basswood, birch, poplar, sweetgum, willow, and hawthorn

Oak Wilt: Attacks Red oak, White oak, Shingle oak and Post oak (has been found in every Illinois county)

Less Major Threats in Illinois:

Asian Long-Horned Beetle

Fall Webworm and Eastern Tent Caterpillar

Lecanium Scale

Magnolia Scale

Pine Wilt Disease (chronic problem affecting Scots, Austrian, jack, mugo and red pines and also to a lesser degree white pines)

Verticillium Wilt
Viburnum Leaf Beetle

Yellow Poplar Weevil

Watch for: Insects and Diseases with the Potential to Impact Illinois

Diagnosing Tree Health
  1. Ash - See additional information on Emerald Ash Borer in the Federal Quarantine Section # 1.
  2. Elm
  3. Sugar Maple - See additional information on Asian Longhorned Beetle in the Federal Quarantine Sec. # 1.
  4. Basswood
  5. Oak - See additional information on Gypsy Moth, Oak Wilt, Sudden Oak Death Syndrome and Thousand Canker Disease in Section # 2.
  6. Honey Locust

Research on Forest Health Related Topics

Sudden Oak Death:

Attacks: broad range of hardwoods, softwoods, landscape and herbaceous plants

European Gypsy Moth:

Attacks more than 300 species of trees and shrubs including fruit trees, oak, aspen, birch, cedar, cottonwood, larch, poplar and willow.

Light Brown Apple Moth: Attacks more than 2,000 species of plants and trees and 250 agricultural crops.

Spotted Lanternfly:

Attacks fruit crops and trees

Thousand Canker Disease:

This is a fungal disease transmitted by the tiny Walnut Twig Beetle.

Attacks all walnuts with the Eastern Black walnut being the most susceptible and the rare butternut.

Common Shoot Beetle (quarantine recently extended to Illinois)

2. Insects and Diseases Currently of Concern to Illinois Forestry.
MAJOR THREATS IN ILLINOIS:
Bacterial Leaf Scorch (10 Illinois counties have this in southern and central Illinois)
Gypsy Moth

: Attacks oak, apple, alder, basswood, birch, poplar, sweetgum, willow, and hawthorn

Oak Wilt: Attacks Red oak, White oak, Shingle oak and Post oak (has been found in every Illinois county)

Less Major Threats in Illinois:

Asian Long-Horned Beetle

Fall Webworm and Eastern Tent Caterpillar

Lecanium Scale

Magnolia Scale

Pine Wilt Disease (chronic problem affecting Scots, Austrian, jack, mugo and red pines and also to a lesser degree white pines)

Verticillium Wilt

Viburnum Leaf Beetle

Yellow Poplar Weevil

3. Watch for: Insects and Diseases with the Potential to Impact Illinois
4. Diagnosing Tree Health

5. Research on Forest Health Related Topics