Emerald Ash Borer
Banded Elm Bark Beetle
The Banded Elm Bark Beetle has been detected in Michigan.
Blue Spruce Diseases
Colorado blue spruce is a popular tree species planted for windbreaks, screens and general landscape purposes. Unfortunately, blue spruce is susceptible to several diseases and insect pests. To learn more about these diseases and how to control them view the Spruce Problems handout compiled by the WCCD.
Diplodia Tip Blight
The fungus, Sphaeropsis sapinea (also known as Diplodia pinea) can cause serious damage to Austrian, ponderosa, red, Scots, mugo, jack, and white pine.
Eastern Tent Caterpillar (Malicosoma americanum)
The native eastern tent caterpillar may be found on fruit trees like apple, chokecherry, crabapple, plum and cherry in May and June. Larvae feed on leaves and make a noticeable web or ‘tent’ in the branches. However, these caterpillars generally do not affect tree health.
Emerald Ash Borer
European Pine Sawfly
This sawfly primarily defoliates jack, red, mugo, & Scotch pine, but will feed on other pines as well. Although the larvae look like caterpillars, they actually belong to the insect order Hymenoptera, which includes ants, bees and wasps. This means that insecticides labeled for control of caterpillars will likely not be effective (for example, the bacterial insecticide BT, or Bacillus thuringiensis, only affects caterpillars). So make sure the insecticide you choose to use lists sawflies on the label!
Forest Tent Caterpillar
The forest tent caterpillar is a native species found throughout hardwood forests of North America. Outbreaks occur about every 10 years and last for 2-4 years. The larvae feed on the leaves of many trees, but prefer aspen, birch, basswood, sugar maple and oak stands.
Hemlock Woolly Adelgid
The Hemlock Woolly Adelgid has been discovered in several Michigan locations and the Department of Agriculture and Rural Development has instituted a quarantine related to this pest.
Oak Wilt
This is an aggressive disease that affects many species of oak. It is one of the most serious tree diseases in the eastern United States, killing thousands of oaks each year in forests, woodlots, and home landscapes. Oak wilt is caused by the fungus, Bretziella fagacearum, which is spread by sap-feeding beetles that carry spores to fresh wounds. However, once infected an oak tree can spread the disease to other surrounding oaks via root graphs. It's extremely expensive to stop, so prevention is key! Plan pruning, construction, or any other activity that may injure oaks between November 1 and March 14 to reduce the risk of contracting oak wilt.
Sirex Woodwasp
This insect attacks Scotch and Austrian pines almost exclusively. More information is available at:
Spongy Moth (formerly Gypsy Moth)
The invasive spongy moth has been a primary defoliator of hardwoods in the Northeastern United States since its introduction in 1869.
Spruce Decline, Diseases & Pests
Spruce trees are experiencing decline throughout Michigan from a variety of maladies—including several needle cast and canker diseases; gall aphids and spider mites. To learn more about what may be affecting your spruce trees, view the Spruce Problems handout prepared by the Conservation District.
Thousand Cankers Disease
This disease has the potential in impact black walnut trees in Michigan.
White Pine Shoot Borer (Eastern Pineshoot Borer)
Other Insect & Disease information
The Banded Elm Bark Beetle has been detected in Michigan.
- Banded Elm Bark Beetle (USDA Forest Service, Pest Alert, 2006)
Blue Spruce Diseases
Colorado blue spruce is a popular tree species planted for windbreaks, screens and general landscape purposes. Unfortunately, blue spruce is susceptible to several diseases and insect pests. To learn more about these diseases and how to control them view the Spruce Problems handout compiled by the WCCD.
Diplodia Tip Blight
The fungus, Sphaeropsis sapinea (also known as Diplodia pinea) can cause serious damage to Austrian, ponderosa, red, Scots, mugo, jack, and white pine.
- Diplodia (Sphaeropsis) Tip Blight (PennState Extension, 2017)
- Diplodia Tip Blight (Cornell University, Plant Disease Diagnostic Clinic, 2015)
Eastern Tent Caterpillar (Malicosoma americanum)
The native eastern tent caterpillar may be found on fruit trees like apple, chokecherry, crabapple, plum and cherry in May and June. Larvae feed on leaves and make a noticeable web or ‘tent’ in the branches. However, these caterpillars generally do not affect tree health.
- Eastern Tent Caterpillars (University of Minnesota Extension, 2018)
- Eastern Tent Caterpillar (PennState Extension, 2002)
- Eastern Tent Caterpillar (MSU, Integrated Pest Management, 2015)
Emerald Ash Borer
- Guidelines for effectively using insecticides to manage EAB are described in Insecticide Options for Protecting Ash Trees From Emerald Ash Borer (May 2009)
- My Ash Tree is Dead, Now What Do I Do? (MSU Extension, 2007)
- Emerald Ash Borer and Your Woodland (MSU Extension, 2005)
- EAB web site, Michigan Department of Agriculture & Rural Development
- EAB Cost Calculator - Compare costs of various removal and treatment scenarios (Purdue University)
European Pine Sawfly
This sawfly primarily defoliates jack, red, mugo, & Scotch pine, but will feed on other pines as well. Although the larvae look like caterpillars, they actually belong to the insect order Hymenoptera, which includes ants, bees and wasps. This means that insecticides labeled for control of caterpillars will likely not be effective (for example, the bacterial insecticide BT, or Bacillus thuringiensis, only affects caterpillars). So make sure the insecticide you choose to use lists sawflies on the label!
- European Pine Sawfly, Neodiprion sertifer (University of Wisconsin-Madison, WI Horticulture)
- European Pine Sawfly (Penn State Extension)
Forest Tent Caterpillar
The forest tent caterpillar is a native species found throughout hardwood forests of North America. Outbreaks occur about every 10 years and last for 2-4 years. The larvae feed on the leaves of many trees, but prefer aspen, birch, basswood, sugar maple and oak stands.
- Forest Tent Caterpillar (University of Minnesota Extension, 2018)
- Forest Tent Caterpillar (USDA Forest Service, Forest Insect & Disease Leaflet 9, 1978)
- Comparison of the Eastern Tent Caterpillar, Forest Tent Caterpillar, and Gypsy Moth (MSU Extension, 2001)
Hemlock Woolly Adelgid
The Hemlock Woolly Adelgid has been discovered in several Michigan locations and the Department of Agriculture and Rural Development has instituted a quarantine related to this pest.
- Hemlock Woolly Adelgid (Michigan Invasive Species, 2023)
- Hemlock Woolly Adelgid (USDA National Invasive Species Information Center, 2020)
Oak Wilt
This is an aggressive disease that affects many species of oak. It is one of the most serious tree diseases in the eastern United States, killing thousands of oaks each year in forests, woodlots, and home landscapes. Oak wilt is caused by the fungus, Bretziella fagacearum, which is spread by sap-feeding beetles that carry spores to fresh wounds. However, once infected an oak tree can spread the disease to other surrounding oaks via root graphs. It's extremely expensive to stop, so prevention is key! Plan pruning, construction, or any other activity that may injure oaks between November 1 and March 14 to reduce the risk of contracting oak wilt.
- WCCD Article with Additional Links (WCCD, 2021)
- Oak Wilt PDF (USFS Forest Health Protection, 2011)
Sirex Woodwasp
This insect attacks Scotch and Austrian pines almost exclusively. More information is available at:
- Sirex woodwasp - Let's Wait and See... (MSU Extension, 2007)
- Sirex Woodwasp (New York State Department of Environmental Conservation)
- Sirex Woodwasp (USDA National Invasive Species Information Center, 2020)
Spongy Moth (formerly Gypsy Moth)
The invasive spongy moth has been a primary defoliator of hardwoods in the Northeastern United States since its introduction in 1869.
- Spongy Moth: Summer 2022 Update (Penn State Extension, 2022)
- Dealing with Spongy Moth Around Your Home or Property (MSU Extension, Integrated Pest Management, 2022)
- WCCD Article with Additional Links (WCCD, 2021)
Spruce Decline, Diseases & Pests
Spruce trees are experiencing decline throughout Michigan from a variety of maladies—including several needle cast and canker diseases; gall aphids and spider mites. To learn more about what may be affecting your spruce trees, view the Spruce Problems handout prepared by the Conservation District.
Thousand Cankers Disease
This disease has the potential in impact black walnut trees in Michigan.
- Thousand Cankers Black Walnut Disease
- Thousand Cankers Disease (USDA Forest Service, Pest Alert, 2011)
White Pine Shoot Borer (Eastern Pineshoot Borer)
- Eastern Pineshoot Borer(USDA Forest Service, Forest Insect & Disease Leaflet 134)
Other Insect & Disease information
- Forest Pests(Michigan DNR, Michigan Forest Health News, August 2011)
- Directory of Exotic Forest Insects and Disease Pests(MSU Extension, June 2002)
