Emerald Ash Borer
Other Pests and Diseases
There are numerous pests and diseases of ash that induce symptoms similar to those produced by the emerald ash borer. It is worth noting that when determining whether emerald ash borer is present you will typically find a combination of at least two of the characteristic symptoms or signs. Conversely, there are numerous insects commonly misidentified as the emerald ash borer due to their similar shape and metallic green color. Fortunately, these insects are not directly associated with ash trees so their misidentification can typically be avoided.
EAB Look-Alike Poster [PDF, 228KB]
Insect Pests
Commonly encountered wood-boring and phloem-feeding insect pests of ash include moth, beetle and fly larvae. Some distinguishing characteristics between these pests and the emerald ash borer are gallery architecture and exit-hole size and shape. The gallery architecture of emerald ash borer is S-shaped and occurs in the phloem tissue, whereas the other ash pests tend to have a more random gallery pattern and/or tunnel into the sapwood. The exit hole of emerald ash borer is D-shaped, while the other ash pests have a more circular shape. The following pests are the most commonly observed under the bark of ash trees:
Clearwing moths (Lepidoptera: Sesiidae)
- Banded Ash Clearwing (Podosesia aureocincta)
- Ash borer (trunk borer) (Podosesia syringae)
Thumbnails link to larger images.
- Adult clearwing moths. Colorado State University Photo by Whitney Cranshaw www.forestryimages.org
- Clearwing moth larva in gallery. Photo by David Cappaert www.forestryimages.org
- Clearwing moth circular exit hole. WDNR Photo by Renee Pinski
- Clearwing moth exit hole with protruding pupal case. WDNR Photo by Renee Pinski
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Bark beetle (Coleoptera: Curculionidae)
- Eastern ash bark beetle (Hylesinus aculeatus)
- Northern Ash Bark Beetle (Hylesinus criddlei)
- White-Banded Ash Bark Beetle (Hylesinus fasciatus)
Thumbnails link to larger images.
- Adult ash bark beetle. USDA Forest Service Photo by James Solomon www.forestryimages.org
- Ash bark beetle circular exit holes. USDA Forest Service Photo by James Solomon www.forestryimages.org
- Ash bark beetle galleries. WDNR Photo by Renee Pinski
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Long-horned beetles (Coleoptera: Cerambycidae)
- Redheaded ash borer (Neoclytus acuminatus)
- Banded Ash Borer (Neoclytus caprea)
Thumbnails link to larger images.
- Redheaded ash borer adult. Hungary Forest Research Institute Photo by Gyorgy Csoka www.forestryimages.org
- Redheaded ash borer circular exit holes. USDA Forest Service Photo by James Solomon www.forestryimages.org
- Redheaded ash borer galleries. WDNR Photo by Renee Pinski
- Banded ash borer adult and its galleries on end of infested log. USDA Forest Service Photo by James Solomon www.forestryimages.org
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Diptera: Agromyzidae
- Ash cambium miner (Phytobia spp.)
- Ash cambium miner galleries. USDA Forest Service Photo by James Solomon www.forestryimages.org
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Disease, Decline and Environmental Stressors
Fungi, phytoplasmas and environmental stressors can also negatively affect ash tree vigor in Wisconsin. These biotic and abiotic agents typically cause gradual decline and branch dieback, symptoms similar to those caused by emerald ash borer. Thus, it is important to look for additional characteristic symptoms caused by the beetle, such as D-shaped exit holes on the bark or S-shaped larval galleries beneath. The following diseases and abiotic stressors are the ones that most commonly affect ash trees in Wisconsin:
- Ash yellows (phytoplasmas) Fact Sheet [exit DNR]
- Brooming symptom of ash yellows on ash. Note the lack of apical dominance in the brooms that is typical of ash yellows. WDNR Photos by Mark Guthmiller and Renee Pinski
- Verticillium wilt (Verticillium dahliae, V. albo-atrum) Fact Sheet [exit DNR]
- Brown streaking evident in stem of branch infected with the verticillium wilt fungus. USDA Cooperative Extension Slide Series Photo by Clemson University www.forestryimages.org
- Ash decline or dieback caused by multiple biotic and abiotic agents including combinations of drought stress, phytoplasmas, viruses, fungal pathogens, freeze damage and pollutants. Fact Sheet [exit DNR]
- Drought (environmental)
- Drought stress on ash trees often results in tufted foliage at the branch tips.WDNR Photo by Renee Pinski
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For additional information on the above pests and diseases of ash, please visit Ash Pests: A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury [exit DNR]
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