Insect and disease issues affecting trees in MnDOT rights of way
The health and aesthetic qualities of trees on MnDOT rights of way and other MnDOT managed lands can be negatively affected by harmful insects and diseases. Some MnDOT construction projects may be located in areas where these harmful insects or diseases are present. Depending on the location of the project and the scope of work involved there may be specifications, special provisions or other state agency regulations tied to a specific project to help control the spread of these insects or diseases.
Emerald Ash Borer
In May, 2009 Emerald Ash Borer was confirmed in Minnesota and has since spread to several areas around the state including ash trees growing on MnDOT rights of way. To help slow the spread of EAB, shortly after the initial discovery in 2009, the Minnesota Department of Agriculture created a quarantine for the affected counties and continues to update those quarantined areas as necessary.
MnDOT projects that take place within a quarantined county where clearing and grubbing (MnDOT Standard Specification 2101) is included, requires the contractor to obtain an Emerald Ash Borer Compliance Agreement from the MDA if the contractor will be transporting any part of an ash tree outside of the quarantine.
The distinct S-shaped galleries under the bark are diagnostic of EAB
Oak wilt
Due to the threat of oak wilt on MnDOT projects where oak trees may be impacted, MnDOT Standard Specification 2572.3A.9 requires that contractors avoid wounding oak trees between April and the end of July to prevent the spread of the disease. Where avoidance is not possible, the contractor is required to treat any wounds with an acceptable wound dressing material. MnDOT Standard Specification 2101.3D.2.b also puts restrictions on the disposal of oak trees on MnDOT projects.
Other insects and diseases that could impact trees in MnDOT rights of way
Insects
- Pine Bark Beetles
- Japanese Beetles
- Twolined Chestnut Borer
- Bronze Birch Borer
- Sawflies
- Fall Webworms
- Gypsy Moth
Diseases
- Dutch Elm Disease
- Bur Oak Blight
- Bacterial Leaf Spots
- Cankers
- Black knot
- Various diseases of Spruce trees