Emerald Ash Borer Risk Status in Minnesota

Current status: Low Activity

Current activity period began October 1, 2017.
Next update expected May 1, 2018.



What is emerald ash borer?
Emerald ash borer (EAB) is a non-native insect transported from Asia to the US and identified in Michigan in 2002. EAB feeds on the tissue of ash trees between the bark and sapwood and disrupting the nutrient and water flow of the tree, eventually killing the tree after several years of feeding in the trees.

What do the Active and Low Activity periods mean?
The activity level of EAB helps us decide when it is safest to work with ash trees.

EAB Active Period: May 1 – September 30

  • Avoid the removal of ash branches, stumps or trees. This is because insects may fly and infest nearby ash trees.
  • If removal is required,
    • Prune and remove ash trees if absolutely necessary.
    • Chip at least the outer 1” of bark and wood on-site and transport to nearest ash tree waste disposal site where they will quickly process the material
    • Or, transport at least outer 1” of bark/wood in an enclosed vehicle to the nearest ash tree waste disposal site that can quickly process the material. Material should be sealed until it can be chipped.

EAB Low Activity Period: October 1 – April 30

  • Prune and remove ash trees as needed
  • Transport at least 1” of bark/wood to the nearest ash tree waste disposal site where is will be taken care of before May 1st.

Ultimately, the identification of the Active and Low Activity periods helps to reduce the spread of EAB. If a tree is left alone during the Active Period, then EAB has a place to lay eggs and reside. But, because the adults will not emerge for one year, if the tree is cut down during the Low Activity Period, the eggs and adults will not have a chance of surviving and spreading.

Do the pruning and removal guidelines apply to the whole state?
It is important to follow the pruning and removal guidelines throughout Minnesota because the signs and symptoms of EAB can lay dormant in the tree for up to five years. It takes a year alone for the larvae to move throughout the tree. Trees can be different sizes and may react to the insect differently. If the tree is infested but not showing signs of EAB, pruning and transporting ash wood during the Active Period can move EAB to a region of the state which EAB was not present before. Without proper precaution this can infest a new set of ash trees. It is important to adhere to the removal guidelines and keep ash firewood in one spot.

Which counties are considered EAB quarantined in Minnesota?
A quarantine is a temporary rule intended to help prevent a potentially dangerous or destructive pest or disease from spreading outside of a known infested area into new areas. EAB quarantines are designed to limit the movement of potentially infested firewood or other materials such as live wood, which might hold EAB larvae. To view the most recent update of the EAB quarantined areas, visit the Minnesota Department of Agriculture’s EAB status page located here.

Will “painting” the pruning wounds reduce the EAB risk if the tree is pruned in the high risk season?
No. Painting pruning wounds on a tree will not reduce the risk of EAB infesting the tree during the Active period. Painting any tree wounds is not recommended with the exception of wounds to oak trees during the high risk period for oak wilt.

Are any of our native ash trees (black, green, white) resistant to EAB?
No. EAB infests and kills all species of ash trees in Minnesota, including black, green and white ash.

Does the emerald ash borer attack mountain-ash and wafer-ash?
No. The mountain-ash and wafer-ash are not truly part of the Fraxinus genus.

Are there any ash trees that are resistant to EAB to some degree?
According to research from Ohio State University, Manchurian ash and blue ash offer some resistance to EAB to different degrees. Manchurian ash may be the most resistant to EAB.

What is the best way to handle the ash logs and debris once the tree has been removed or pruned?
The best way to handle ash logs and debris is to send them to the nearest ash tree waste disposal site to have them processed before May 1st in the Low Activity period. If you are dealing with this debris during the Active period, it is important to seal the debris and logs and transport them to the nearest facility to be processed immediately.

Is there any control for EAB once it’s in the tree?
It may be helpful to use insecticides in the early stages of infestation. But keep in mind that once the insect infests the tree, the damage which is caused is irreversible. If the tree begins to show symptoms of damage such as canopy dieback beyond 30%, it may not be helpful to inject insecticides because of the volume of tissue loss and decreased ability for the tree to move the insecticide, nutrients, and water throughout the tree. Before canopy dieback reaches 30%, insecticides have been shown to be successful.

Is there any treatment to prevent EAB from entering and damaging an ash tree?
There are two common types of approaches of treatment which target the adult insect. These treatments include tree trunk injections and soil and root drenching applications. It has been found that the injection treatment is less harmful on the environment and gives the tree direct injection into the the tissue of the tree. It is common that the homeowner pay for these services and a licensed professional is needed in order to apply the insecticide.

Is it safe to mill any lumber from the ash tree that has been removed? If so, how?
It is safe to mill the lumber from ash trees if the wood does not leave the county it was cut down from, especially if it is a quarantined county and if the outer 1 ½-inch of sapwood is removed and disposed of to kill any EAB present.

Can the EAB be transported via wood chips?
If moving the ash wood is unavoidable, chipping will be the most cost effective approach and destroys the ability for EAB to reproduce. However, chips must be small enough (2 sided and less than 1-inch) to successfully kill the EAB larvae and/or pupae.

What should I do if I suspect EAB damage on my property?
Contact the Minnesota Department of Agriculture’s Arrest the Pest hotline (888-545-6684; arrest.the.pest@state.mn.us). Note the exact location of the tree and take a digital photo if possible.

Can I add the University of Minnesota EAB risk widget to my site?
Yes! Click here to get the code.

Emerald ash borer image courtesy of Kent Loeffler, Cornell University.