Emerald Ash Borer
Banded Elm Bark Beetle (Scolytus schevyrewi or BEBB)
The Banded Elm Bark Beetle is an invasive insect that was detected in Michigan in 2004. Severe infestations can kill elm trees (Ulmus spp.). In addition, the BEBB may spread the fungus (Ophiostoma novo-ulmi) that causes Dutch elm disease.
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 (Agrilus planipennis or EAB)
EAB is an invasive insect that kills ash trees (Fraxinus spp.) as well as white fringetree (Chionanthus virginicus). EAB likely arrived in the United States hidden in wood packing materials and was first identified in southeastern Michigan in 2002. There are a variety of treatment options that can serve as a control measure, but they are not a cure.
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 (HWA)
HWA is an invasive insect, related to aphids and mealybugs, that sucks sap from hemlock trees. The major hemlock species at risk in the eastern U.S. are eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana). In 2023, HWA was found at the U-M Nichols Arboretum near Ann Arbor.
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.
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.
Thousand Cankers Disease (TCD)
TCD is a fungal disease of walnuts (Juglans spp.) that is carried from tree to tree by a small bark beetle called the walnut twig beetle (Pityophthorus juglandis). The disease can go undetected in a tree for several years. Once symptoms are visible, the tree will likely die in about 3 years since there is currently no treatment. As of 2023, this disease has not yet been discovered in Michigan, but has been confirmed in Ohio.
White Pine Shoot Borer/Eastern Pineshoot Borer (Eucosma gloriola)
This moth attacks various Michigan native or introduced pines, including eastern white (Pinus strobus), jack (Pinus banksiana), red (Pinus resinosa), Austrian (Pinus nigra), mugho (Pinus mugo), and Scots (Pinus sylvestris) pines. The moth larvae tunnel into new shoots, killing them. The shape of the tree's main trunk becomes deformed when the terminal leader is killed which is especially problematic for Christmas tree farms.
Other Insect & Disease information
The Banded Elm Bark Beetle is an invasive insect that was detected in Michigan in 2004. Severe infestations can kill elm trees (Ulmus spp.). In addition, the BEBB may spread the fungus (Ophiostoma novo-ulmi) that causes Dutch elm disease.
- 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 (Agrilus planipennis or EAB)
EAB is an invasive insect that kills ash trees (Fraxinus spp.) as well as white fringetree (Chionanthus virginicus). EAB likely arrived in the United States hidden in wood packing materials and was first identified in southeastern Michigan in 2002. There are a variety of treatment options that can serve as a control measure, but they are not a cure.
- 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 (HWA)
HWA is an invasive insect, related to aphids and mealybugs, that sucks sap from hemlock trees. The major hemlock species at risk in the eastern U.S. are eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana). In 2023, HWA was found at the U-M Nichols Arboretum near Ann Arbor.
- 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.
- 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.
Thousand Cankers Disease (TCD)
TCD is a fungal disease of walnuts (Juglans spp.) that is carried from tree to tree by a small bark beetle called the walnut twig beetle (Pityophthorus juglandis). The disease can go undetected in a tree for several years. Once symptoms are visible, the tree will likely die in about 3 years since there is currently no treatment. As of 2023, this disease has not yet been discovered in Michigan, but has been confirmed in Ohio.
- Thousand Cankers Disease Website (Collaborative effort between multiple agencies and groups, 2023)
- Thousand Cankers Disease (USDA, 2022)
White Pine Shoot Borer/Eastern Pineshoot Borer (Eucosma gloriola)
This moth attacks various Michigan native or introduced pines, including eastern white (Pinus strobus), jack (Pinus banksiana), red (Pinus resinosa), Austrian (Pinus nigra), mugho (Pinus mugo), and Scots (Pinus sylvestris) pines. The moth larvae tunnel into new shoots, killing them. The shape of the tree's main trunk becomes deformed when the terminal leader is killed which is especially problematic for Christmas tree farms.
- Eastern Pineshoot Borer (USDA Forest Service, Forest Insect & Disease Leaflet 134)
Other Insect & Disease information
- Forest Health (Michigan DNR, 2023)
- Directory of Exotic Forest Insects and Disease Pests (MSU Extension, June 2002)
