Invasive Species

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Invasive Species, Diseases, & Pests

Emerald Ash Borer
garlic mustard
dutch elm and oak wilt

Emerald Ash Borer beetle
At this point, most ash trees in Columbia Heights have likely been infected by the EAB beetle. If there's still a chance to save a tree on your property through chemical treatment, action must be taken now . If it's too late to treat your ash trees, the next and only option left is tree removal. Please call the Urban Forester at 763 -706-3722 for free consulting on the health of ash trees on your property and if they still have a chance to be saved through chemical treatment.

What This Means for Your Ash Trees?

There’s little time to spare. Untreated ash trees in Columbia Heights will likely die within the next one to four years. If they’re already showing noticeable signs of infestation, it’s probably too late for preventive treatment. When ash trees show visible signs of infestation, they decline very quickly. They get brittle, more expensive to remove, and more likely to lose branches during a storm, which turns them into safety hazards and liabilities. The longer residents wait to remove dead trees, the more expensive and dangerous it gets. 

Two Viable Paths Forward for Your Ash Trees:

  1. Preventative Chemical Treatment 

    This option is cheaper than tree removal and gives you the best chance of saving ash trees on your property. Chemical Treatment Systemic trunk injections of emamectin benzoate 4% performed by a licensed and bonded tree care expert once every three years can be highly effective in treating and preventing EAB infections. Treatments will have to be repeated every three years as long as EAB populations remain high in the area, likely ten years at a minimum. Mid-May to mid-June is the optimal time for injections in Minnesota. Please keep in mind that chemical treatments are only effective on ash trees that are still healthy or only lightly to moderately affected by EAB. Consult an ISA certified arborist or the City’s forester (763 706-3722) to determine if your ash trees are good candidates for treatment. Visit for more info on a citywide discount for residents from Rainbow Treecare. 

  2. Removal

    If the tree is already showing noticeable signs of disease resulting from EAB, the only viable option is removal. The best time to remove trees is during the dormant season, January to March. Tree removals in Columbia Heights must be performed by contractors licensed to work within the City. Always choose a licensed, bonded, and insured tree care professional and seek multiple estimates if possible. Keep in mind, Anoka County is under formal EAB quarantine established by the MN Department of Agriculture. All wood and waste from ash tree removals are subject to regulation under the MDA quarantine and must be disposed of properly. Use licensed contractors for tree removal. Find a list of local licensed tree care contractors here

EAB Removal Program

Identifying Infestations
Residents are encouraged to look at their ash trees for signs of EAB. Checking for EAB, reporting possible infestations, and following quarantines can slow the spread of EAB.

  • When checking for EAB: Be sure you’ve identified an ash tree. EAB only feeds on ash trees.
  • Look for woodpecker damage. Woodpeckers like EAB larvae and woodpecker holes may indicate the presence of EAB.
  • Check for bark cracks. EAB larvae tunneling under the bark can cause the bark to split open, revealing the larval (S-shaped) tunnels underneath.
  • Look for branches spouting from the middle of tree while top branches are thinning

If you feel your ash tree may be infested with EAB, visit or call 888-545-6684.

Tips to Keep EAB From Spreading
The biggest risk of spreading EAB comes from people unknowingly moving firewood or other ash products harboring larvae.

  • Don’t transport firewood. Buy firewood locally from approved vendors and burn it where you buy it.
  • Be aware of the quarantine restrictions. If you live in a quarantined county, be aware of the restrictions on the movement of products such as ash trees, wood chips, and firewood. Anoka County is under quarantine.

For detailed information about EAB identification, treatment and/or removal options, please visit

City's EAB Management Plan for Public Spaces
The City of Columbia Heights has been preparing for the ash borer's arrival since 2013, when City leaders adopted a plan to prepare for and manage it. Crews have removed unhealthy ash trees and used two-year, ongoing cycle treatments for larger, healthy trees. This spring, Columbia Heights finished removing all ash trees on public property that were marked for removal, with all remaining public ash trees chemically treated to protect from EAB. The City planted nearly two new trees of multiple varieties on public land for every one ash tree that was removed. It's now up to private property owners to manage the remaining ash trees in Columbia Heights. 

More Resources and History of EAB
The invasive Emerald Ash Borer beetle was discovered in Columbia Heights in 2019. At the time, the City had an estimated 5,000 ash trees within the City limits, most on private property. EAB (Agrilus planipennis Fairmaire) was introduced to the United States from Asia and first detected in southeast Michigan in June 2002.  This destructive beetle has killed tens of millions of ash trees where it has been discovered.
EAB was discovered in St. Paul in May 2009. There are approximately 870 million ash trees in Minnesota, one of the largest concentrations of any state in the country. All ash trees not chemically treated for EAB will eventually succumb to EAB. 

Select the following links for more information:, EAB University webinars. Or find more information here:                       

For specific questions or consultation, call the Urban Forestry Specialist at 763-706-3722 or email For questions about firewood regulations, contact the Minnesota Department of Agriculture at 651-201-6684 (metro) or 888-545-6684 (greater Minnesota).


Buckthorn is a non-native shrub brought from Europe in the mid-1800s for use as a hedge or windbreak plant. It forms dense thickets and will out-compete native shrubs, tree seedlings, and perennials such as wildflowers for sunlight, water, and soil nutrients. Buckthorn became a restricted noxious weed in 2001 and can't be purchased in Minnesota. Common buckthorn and glossy buckthorn are the two species of interest. They can be easily identified because they leaf out earlier in the spring than most native plants and retain green leaves well into November. Berries have a laxative effect on birds and seeds are distributed widely each year. Seeds can remain alive in the soil for more than six years.

Buckthorn is found throughout the Metro Area. For more about Buckthorn identification, removal, and treatment, visit the MN DNR's buckthorn management page here

garlic mustard
Garlic mustard is an aggressive biennial herbaceous (or herb) plant, which means it does not flower until its second year and then it dies. It grows in a way that crowds out native wildflowers, tree seedlings, and woodland plants and can totally dominate a woodland within five to seven years. Garlic mustard is found throughout the Metro Area. For more about garlic mustard identification, removal, and treatment, visit the MN DNR's garlic mustard management page here. For more information about State Prohibited Noxious Weeds, go here

dutch elm and oak wilt diseases
Dutch Elm and Oak Wilt diseases are caused by fungi carried by an insect from tree to tree. Once the elm is infected, the fungus grows rapidly in the water-conducting vessels of the entire tree. The vessels clog and the tree wilts and dies. The diseased tree then becomes a breeding site for more insects that will transfer the disease to healthy trees. These diseases continue to spring up throughout Minnesota. The first symptom in trees infected with Dutch elm disease is usually a small area of yellow or brown wilting foliage called “flagging,” often beginning with a branch on the edge of the crown. The area expands and progresses toward the trunk. Wilted branches may have brown streaking in the sapwood which can be seen if the bark is removed. The University of Minnesota plant disease clinic can test elm samples for Dutch elm disease. For more information on disease identification and management, visit the MN DNR's Dutch elm and oak wilt management page here

For specific questions or local consultation, call the Urban Forestry Specialist at 763-706-3722 or email For questions about firewood regulations, contact the Minnesota Department of Agriculture at 651-201-6684 (metro) or 888-545-6684 (greater Minnesota).