Forestry

City of Gem Lake Forestry

Many species of trees make up the City’s urban forest. Many native species, including oak, elm, basswood, maple, and paper birch, can be found in remnant forest parcels. Numerous nursery varieties have been planted by landowners. Each tree species comes with its own set of characteristics and problems.

Tree Inspection

The City of Gem Lake contracts its services to White Bear Township Public Works who provide free tree inspection for concerns or questions you may have about your trees. The Township routinely inspects all properties for oak wilt and Dutch elm disease. Township inspectors are watching for emerald ash borer symptoms in ash trees.

Emerald Ash Borer (EAB)

History

Emerald Ash Borer (EAB) has decimated the Ash trees in Minnesota. Native to Asia, it is likely the pest came over in wood packing material. The first U.S. identification was in Michigan in 2002 with its first confirmed appearance in Minnesota in 2009.

Emerald Ash Borer

Emerald ash borer (EAB) is an aggressive and invasive beetle that infects and kills ash trees. EAB attacks all species of North American Ash. EAB eggs are laid on the bark or in small cracks. Once larvae emerge from their egg, they tunnel into the cambial layer of the tree (the layer beneath the bark). The larvae are 1” to 1 1/4” when fully grown with a flat body and brownish head. At this point in development, the beetle has no legs. The larvae wind back and forth as they feed under the bark and create distinct, S-shaped tunnels in the wood and cutting off nutrient flow throughout the tree. Larvae feed under the bark until late fall and then winter in the tunnels they created. The fully-grown larvae live through the winter in these tunnels, transforming into pupae the following spring and from there into an adult. The adult beetle is a small green beetle that is not often seen. The adult beetle is 1/3” to 1/2” long with a slender body. They are bright green in color and may have a copper color just behind its head.

Symptoms of EAB infestation

White Bear Township has found EAB throughout the City. On average, trees are killed within four years of being infested, though complete devastation can happen between two and five years. When first infected, symptoms are hard to notice, but often begin with blonding. Blonding is seen as light patches of bark often starting at the top of the tree. During the second year you may start to notice increased woodpecker activity and foliage thinning. By year three, canopy thinning is pronounced as is greater woodpecker activity. By the fourth year, canopy dieback has greatly increased, and you may see vertical bark splits in the main trunk.

What to do if you are concerned you have EAB?

First is to confirm that your tree is an Ash tree. Once confirmed, you can choose to treat or remove the tree. Treatment of a tree can be done proactively or during early infestation. Lightly infested trees that show little signs of decline can recover if treated. Infested trees with more than 50% of canopy dieback are not favorable for treatment. While treatment may be an option, it should be noted that treatment cannot reverse damaged that has been already caused by the EAB. The decision to treat, remove, or retain private trees rests with the property owner. Homeowners can use any tree contractor that is licensed in the City.

Arrest the Pest Hotline

Residents should learn about this threat to our ash trees and be on the lookout for infested trees. If you suspect a possible EAB infestation, call the MDA “Arrest the Pest Hotline” at 651-201-6684 Metro Area, or 888-545-6684 Greater Minnesota or Email Arrest the Pest.

Helpful Links

Dutch Elm

History

Dutch elm disease was first found in Minnesota during 1961 in St. Paul and can now be found throughout Minnesota. The spread of Dutch elm disease in Minnesota was documented by the University of Minnesota.

Dutch Elm

Dutch elm disease is caused by a fungal invasion of an elm tree’s water conducting vessels. Dutch elm disease is exclusive to elm trees and does not pose any risk to other tree species. Once disease symptoms are observed, tree death can occur in as little as a few weeks. When a tree detects the fungus, it responds by plugging its vessels to keep the fungus contained, but the fungus remains ahead of the tree and essentially the tree causes its own death by cutting off the water supply.

Signs of Dutch Elm Disease

Dutch elm disease symptoms appear 4-6 weeks after infection. The first noticeable symptom is wilting or “flagging” of one or more branches in the upper canopy of the tree. Leaves then turn dull green to yellow and brown, resulting in premature leaf fall. As the infection spreads, the wood beneath the bark becomes discolored as a result of fungal staining. 

Residents should learn about this threat to our elm trees and be on the lookout for infested trees. If you suspect Dutch elm disease, call the MDA “Arrest the Pest Hotline” at 651-201-6684 Metro Area, or 888-545-6684 Greater Minnesota or Email Arrest the Pest.

How Does Dutch Elm Spread

DED is spread via beetle transmission and roots grafted with nearby infected trees. The most common method of spread is through beetle transmission. There are at least two kinds of elm bark beetles known to transmit the Dutch elm disease fungus; the European elm bark beetle and the native elm bark beetle. Female beetles lay eggs beneath the bark of dead and dying elm trees and/or firewood with tight bark. Newly hatched beetles emerging from infected elm trees carry the fungus on their body parts. The beetles fly to nearby elm trees to feed causing these trees to become infected with DED. Elm bark beetles feed exclusively on elm trees. Dutch elm disease also can spread into nearby healthy elms through roots that have grown together between two or more trees. 

Helpful Links

Oak Wilt

History

Oak wilt was first discovered in Minnesota around 1945. Today oak wilt is widespread in east-central and southeast Minnesota and continues to expand its range northward. To date, oak wilt covers about one-third of the area where most Minnesota oaks grow.

Oak Wilt

Oak Wilt kills all species of our native oak trees: white oak, swamp white oak, northern pin oak, bur oak, northern red oak.

White Bear Township works to control the spread of this epidemic disease through inspection, and education. The Township has two tree inspectors to identify and mark oaks with oak wilt. When an oak with oak wilt is found, the property owner is sent a letter regarding the tree’s condition and what needs to be done. Removal is usually required, and other measures may be recommended. White Bear Townships tree inspectors work with property owners on how to best manage a stand of oaks that includes an infected oak.

Signs of Oak Wilt

The 1st sign of oak wilt disease is the yellowing of leaves in an isolated branch in the upper canopy. The leaves dry out quickly and turn a dark green or bronze, beginning at the leaf edge and moving toward the midrib and base of the leaf. Leaves may fall or may remain on the dying branch. The branch progressively dies back. Red oaks and pin oaks usually die within a growing season, while bur oaks and white oaks may take several years to die.

Other diseases, pests, or drought can make an oak tree appear to have oak wilt. If you suspect oak wilt, call the MDA “Arrest the Pest Hotline” at 651-201-6684 Metro Area, or 888-545-6684 Greater Minnesota or Email Arrest the Pest.

How Does Oak Wilt Spread?

There are two ways oaks can get infected with Oak Wilt:

Overland: The fungus is carried by the picnic beetle to a fresh wound on a healthy oak between mid-April and early-July. The tree is now infected.

Underground: After that first oak dies, other oaks of the same group – -connected via root grafts – – will be infected. This is what an “Infection Center” is. Rarely will a red oak join with a white oak and form root grafts. The Infection Center grows outward, compounding oak mortality every year. Unless stopped, the problem gets worse.

Every year, the majority of oaks die from root graft spread, not overland spread, of oakwilt disease.

Helpful Links