Be on the lookout for a few very destructive pests. Pests are grouped by the pest, or location and type of the symptoms. To learn more about a forest pest, simply "click" on one of the images found below.

• Insects:

Asian Longhorned Beetle	Balsam Woolly Adelgid (Firs Only)	HemlockWoolly Adelgid (Hemlock Only)

• Foliage Dieback:

Oak Wilt

• Trunk/Bark:

Beech Bark Disease	Sudden Oak Death

Forest Insect Pests

Some forest pests are most easily identifiable by the insect that causes the problems.

Asian Longhorned Beetle (Anoplophora glabripennis)

• Trees Affected: Norway, sugar, silver, and red maple, horsechestnut, aspen (poplar), willow, elm, mulberry, and black locust and other hardwoods.

• Symptoms: Very round rust colored holes (entry and exit wounds) about 3/8 to 1/2" in diameter along the branches or trunk of the tree.

• Importance: Extremely destructive exotic pest that once established can kill hardwoods very rapidly.

• Prevention: Early detection and prompt removal of dead or dying trees.

• Reporting: Please click the image below if you have seen this pest.

• Learn More:

• • Current Status, Research, and Management of the Asian Longhorned Beetle

    Ohio DNR Asian Longhorned Beetle Site
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Adult Asian longhorned beetle on a hardwood tree.

Round rust colored holes left by the Asian longhorned beetle.

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Balsam Woolly Adelgid

• Trees Affected: All true furs, Abies spp., including balsam and fraser fir.

• Symptoms: Infested crowns with abnormal drooping of current shoots and gouting of outer twigs. Crown becomes increasingly thin and dieback may occur. Stem attacks with conspicuous presence of white woolly masses often giving the lower bole a whitewashed appearance. Sapwood of infested wood swells causing gouting of twigs and increased heartwood formation.

• Importance: A serious pest of forest, seed production, landscape, and Christmas trees. Stem infestations are usually more serious, causing greater levels of damage and mortality. Persistent crown infestation can kill a tree over a number of years.

• Prevention: Early detection and prompt removal and destruction of dead or dying trees. Prescribed fire is often used to sanitize the site.

• Reporting: Back to the top of the Page...

Balsam fir bark infected with Balsam Woolly Adelgid.

Gall-like formation on the twigs, due to Balsam Woolly Adelgid feeding.

Balsam fir needles infected with Balsam Woolly Adelgid.

Hemlock Woolly Adelgid

• Trees Affected: Eastern hemlock (Tsuga canadensis) & Carolina hemlock (T. caroliniana).

• Symptoms: White cottony masses at the base of needles.

• Importance: Destructive disease that can quickly kill hemlock.

• Prevention: Early detection and treatments to avert establishment of populations.

• Reporting:

• Learn More:

  • USDA Forest Service Hemlock Woolly Adelgid Site

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Eastern Hemlock needles infected with Hemlock Woolly Adelgid.

Dieback on Eastern Hemlock due to Hemlock Woolly Adelgid.

Foliage Dieback

A number of forest pests directly or indirectly affect the foliage on trees. Some pests eat or chew on the leaves or needles while other pests may injure parts of the tree which led to foliage dieback.

Oak Wilt

• Trees Affected: White, and Red Oak

• Symptoms: Bronzing or browning of green leaves from the tips/margins toward the leaf base.

• Importance: Destructive disease that can kill oaks very rapidly.

• Prevention: Early detection and prompt removal of dead or dying trees. Avoid trimming, or cutting live oak trees during spring (May - June).

• Reporting:

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Oak wilt symptoms on red oak leaves.

Oak wilt defoliation.

Trunk/Bark

The affects of some pests are most noticeable on the bark or trunk of the tree. Often times scales or wholes are left by the pest on or within the bark.

Beech Bark Disease

• Trees Affected: American Beech

• Symptoms: Small white scales are present on the bark of the tree.

• Importance: Very destructive disease that can kill large stands of beech trees.

• Prevention: Early detection and prompt removal of dead or dying trees. Avoid touching the infected tree or trees.

• Reporting:

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Scaling associated with beech bark disease.

White lichen often confused with beech bark disease.

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Sudden Oak Death

• Trees Affected: (Quercus sp., Lithocarpus densiflorus); rhododentrons;
  huckleberry (Vaccinium ovatum); bay laurel (Umbellularia californica); and California buckeye (Aesculus californica); Big leaf maple (Acer macrophyllum); CA honeysuckle (Lonicera hispidula).

• Symptoms: Cankers are formed on stems. Cankered trees may survive for one to several years, but once crown dieback begins, leaves often turn from green to pale yellow to brown within a few weeks.

• Importance: Exotic lethal disease of oaks. Likely difficult to eradicate once established.

• Prevention: Early detection and prompt treatment of site which includes prescribed fire.

• Reporting:

• Learn More:

  • California Oak Mortality Task Force

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Dark spots on bark with exuding brown to tar black
thick sap.

Bleeding or seeping from the main stem or trunk.

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