Tree Diseases, Pests & Invasives

Tree Diseases

Dutch Elm & Oak Wilt Diseases

These 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.

Dutch elm and oak wilt diseases are continuing problems within Golden Valley's urban forest. Over the past several years, the City has experienced losses to Dutch elm disease. With many elm and oak trees remaining in the city, continuation of a comprehensive sanitation program is essential for keeping annual losses to a minimum.


Emerald Ash Borer

The Emerald Ash Borer (EAB) is an invasive beetle that attacks and kills ash trees. Its larvae kill ash trees by tunneling into the wood and feeding on the tree's nutrients. Since its accidental introduction into North America, EAB has killed millions of ash trees in 35 states and the District of Columbia. With almost a billion ash trees in forests and urban areas, Minnesota is a prime target for EAB.

To prevent the spread of Emerald Ash Borer, a state quarantine is in place for Hennepin, Ramsey, and several other additional counties. This means any ash material (trees, logs, branches, chips, mulch, etc) and all hardwood (non-coniferous) firewood is not to be transported outside these quarantined counties. This material may enter the quarantined counties and travel within them; however, once inside the quarantine, it is not allowed to leave.

Spongy Moth

Spongy moths, from the butterfly and moth family, are considered by many experts to be the single most destructive pest of trees and shrubs. They were discovered in Golden Valley, St Louis Park, and Minneapolis in fall 2001. No more were found in the Twin Cities area since the Minnesota Department of Agriculture treated 1,850 acres in May 2002 until fall 2016, when an infestation site was found in Richfield and two other areas in east-central and southeast Minnesota. those three sites were treated in June 2017 to eradicate and slow the spread of spongy moths. At the same time, spongy moths were found in the Lowry Hill area of Minneapolis. In 2019, areas in Lakeville, Stillwater, and Chisolm were treated to slow the spread of spongy moths.



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. Seed can remain alive in the soil for more than six years.

Weed Wrench Program
The City of Golden Valley has weed wrenches available for use by residents. They can be checked out for up to seven days and picked up in the Community Development Department in the lower level of City Hall during office hours (Monday through Friday, 8 am to 4:30 pm). When borrowing a wrench, residents must leave their name, address, phone number, and a $100 security deposit, which will be returned when the wrench is checked in. 

Please call the Engineering Division in advance to ensure there are wrenches available for use at 763-593-3986. 

If you want to remove buckthorn on City property, check out the Buckthorn Abatement Map showing where you can volunteer. Then fill out a Volunteer Form (PDF) and email it to the City Forester.

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. This invasive plant species can be found throughout Golden Valley.