What is the Emerald Ash Borer (EAB) and what does it do?

EAB is a wood boring insect that was accidentally transported from Asia; EAB was first discovered in 2002 in southeastern Michigan and Windsor, Ontario. It infests and kills North American ash species (Fraxinus sp.) including green, white, black and blue ash, and their cultivars. The larval stage of EAB feeds under the bark of ash trees, cutting off the flow of water and nutrients. Infested trees gradually die over a 2–5-year period.

Why should we care? How serious is this?

EAB infestation is fatal to healthy ash trees unless treated. Infested trees will decline from the top tree canopy down and will be dead in approximately 2 to 5 years if not treated, even if the trees were healthy before being attacked by EAB. Ash is a very common tree in many if not all Colorado communities. In Michigan, the first infested state in the U.S, the greatest economic impact has been on communities faced with the removal of thousands of dead ash trees. Many of these dead trees pose significant public safety hazards, liability, and require more expensive removal techniques as a result.

How close is EAB to your property?

EAB was recently discovered in Littleton, CO as of 2023. Please refer to https://www.aphis.usda.gov/aphis/maps/plant-health/eab-storymap for current EAB locations and an abundance of additional information.

Symptoms

EAB-Infested ash trees may have woodpecker holes/damage, bark splits, thinning canopy, D shaped exit holes in bark, and sprouts at the base of the tree. Please visit https://extension.colostate.edu/topic-areas/insects/emerald-ash-borer-resources/ for more information.

Treatment Options

Treatment requires a long-term commitment- You can help protect your ash trees with a variety of systemic insecticide applications. Treatments may be needed for the rest of the tree’s life. Trees have been saved with treatments in infested areas of the Mid-West, but there is not a 100% guarantee with any treatment. There is better evidence of control with trunk injection applications than soil applied applications.

Timing is everything- American Arbor Care’s first level of approach is either a soil injection or a trunk injection depending on the size of the tree. If the tree is under 8” in diameter at breast height we will soil inject, if it is over 8” in diameter we will trunk inject. Soil injections are most effective when applied in March/April, and trunk injections are most effective when applied in May/June. The price for all levels of treatment depends on the tree size.

Remove and replace ash trees on your property- It may be more cost effective to replace a small or struggling ash tree than to pay the cost of ongoing treatments. In addition, trees in poor health are not likely to respond well to treatments.

Which trees should we try to save? Ash trees that are worth treating are healthy and vigorously growing with more than 30-50% of their leaves, enhance the landscape, or are valued by homeowners. Trees that should not be treated are weak/unhealthy ash, planted in poor sites, are not important to the landscape, and those showing signs of EAB infestation.

What can you do to help? Please share this information with your friends, family and property owners. The goal is to get as much information out there so our clients can make informed decisions.

Contact the tree care professionals at American Arbor Care. We have certified arborists on staff. We retain all the required licenses, insurance and qualifications necessary from the State Department of Agriculture to apply pesticides, etc. We are available to answer your questions and concerns surrounding this pest or any other issue surrounding your landscape. Contact us for EAB treatment today.

American elm trees are native to North America, and they can grow to magnificent heights and live for centuries. Unfortunately, they’re susceptible to a devastating disease known as Dutch elm disease, or DED, that can quickly spread and devastate large areas where healthy elms grow. So, what is Dutch elm disease, and how can you prevent it from spreading to your health Denver trees? Our arborists at American Arbor Care are committed to keeping our Colorado elms healthy and strong.

What is Dutch Elm Disease?

Dutch elm disease is caused by a fungus that is spread by elm bark beetles. These tiny pests carry the spores of a fungal pathogen called Ophiostoma novo-ulmi. When an elm bark beetle burrows tunnels through the bark of an American elm tree, it leaves spores behind which quickly infect the tree. DED can infect all species of elms that are native to North America, but American elms are the most susceptible to the fungus. Once a tree has been infected, it quickly deteriorates and dies within three years.

A Brief History of Dutch Elm Disease in Colorado

Around 100 years ago, Denver city officials and local homeowners planted around 100,000 American elm trees throughout the city and state. In 1948, DED was first discovered in the state. Luckily, it died out and did not spread. In 1968, the disease reappeared and wreaked havoc on healthy elms in Denver, but it did not kill them all. Fortunately, Colorado did not have a case of DED for many years. This streak of luck ended in July of 2023, when the Denver City Forester confirmed DED along 17th Avenue in the South Park Hill neighborhood.

How Does Dutch Elm Disease Spread?

Dutch elm disease is a fungal disease that is spread by elm bark beetles. As the beetles fly from tree to tree, they carry spores and leave them behind on the as they burrow tunnels underneath the bark. Adult female elm bark beetles lay eggs under the bark of healthy elm trees, and when they emerge as adults, new beetles are released to infect more trees in the area. It’s a fast-spreading fungal disease that is hard to spot, and infected trees must be treated preventatively in order to be saved.

What Are the Symptoms of Dutch Elm Disease?

Symptoms of DED include:

• Discolored leaves
• Wilting leaves and branches
• Upper canopy leaves that begin to die and turn brown
• Fallen leaves in the spring and summer
• Brown streaking along the sapwood (located underneath the bark of infected branches)

As the disease progresses, branches will begin to die and the tree will quickly decline. An untreated tree with DED will die within two to three years of infection. If you suspect that your tree has been infected, it’s crucial to have an arborist check it out as soon as possible.

How to Save Your Elm Trees from Dutch Elm Disease

There is no cure for DED, but there are preventative treatments to keep it away, and successful treatments to keep the infection at bay. When an elm tree is diagnosed with DED, infected branches must be removed and disposed of properly. This will slow the spread of the disease throughout the rest of the tree and to nearby elm trees. 

At American Arbor Care, we offer preventative trunk injections for healthy elm trees that will effectively prevent the spread of DED. This is the best and most effective treatment option to keep your elm trees from falling prey to DED. If you’d like to know more about DED and you’d like to have your elm trees treated for the disease, we’re happy to help. Contact American Arbor Care today.

Trees are hardy and strong, but it’s important to look out for diseases and pests that could affect them. Let’s take a look at ash anthracnose and how it can affect ash trees in Denver.

Understanding Ash Anthracnose

Ash Anthracnose is caused by a fungus that overwinters on twigs and fallen leaves. It thrives in cool, moist environments. When spring arrives, ash anthracnose appears as wet splotches on the leaves that quickly spread, and it causes young leaves to curl and pucker. The fungus can easily spread from an infected tree to other trees in the area, so it’s important to mitigate the problem quickly. 

Impact on Ash Trees

Ash trees that are infected with anthracnose can suffer from cankers on twigs and a dieback of small branches. It also causes trees to drop their leaves prematurely. If the disease progresses, a tree can experience dieback of the lower branches and complete defoliation. Without proper treatment, anthracnose leaves a tree weak and susceptible to other pests and diseases, and it can quickly spread to other trees in the area.

Ash Anthracnose Life Cycle

Ash anthracnose is a fungus that overwinters on twigs and the stems of leaves. In the wet spring weather, spores spread and infect the tree, leading to a variety of symptoms. Water-soaked spots appear on leaves, twigs develop cankers, and the tree experiences premature defoliation. As the spores spread and leaves fall, the fungus can quickly spread to nearby trees. Ash anthracnose thrives in cool, moist weather, much like the climate here, in Denver. When spring arrives, it quickly spreads.

Importance of Early Detection and Mitigation Strategies

Early detection is key, not only to save a tree from becoming weak and vulnerable, but to avoid further spread of the fungus. To avoid this fungal disease, keep your trees properly pruned, adequately watered, and in good health. A healthy tree is far less susceptible to pests and diseases like ash anthracnose. If you’re worried about ash anthracnose, we’re here to help. Contact the pros at American Arbor Care.

Frequently Asked Questions (FAQs)

What are the early signs of Ash Anthracnose?

Anthracnose appears in the spring, as water-soaked spots on the leaves. Young leaves may also be curled, twisted, and puckered as they begin to grow.

How does Ash Anthracnose affect the structural integrity of trees?

A serious infection can lead to defoliation and dieback in the lower limbs.

Can Ash Anthracnose be transmitted to other tree species?

Ash anthracnose can be transmitted to most ash trees.

Are there specific ash tree varieties more resistant to Ash Anthracnose?

Yes, the green ash is fairly resistant to the fungus.

When is the best time to apply fungicides for Ash Anthracnose prevention?

During the spring when buds begin to appear and the weather is exceptionally wet.

What cultural practices can homeowners adopt to minimize the risk of Ash Anthracnose?

• Don’t overwater your trees.
• Never compost leaves that have been infected.
• Prune away diseased branches and twigs.
• Rake and destroy leaves that fall in autumn.

Are there any natural predators or biological controls for the Ash Anthracnose fungus?

No, the best way to mitigate anthracnose is by keeping the tree healthy, properly pruned, and watered sufficiently.

How frequently should I monitor my ash trees for potential Anthracnose infection?

Check your tree frequently for signs of stress, but especially in the early spring as buds and leaves begin to appear.

Can Ash Anthracnose spread through contaminated tools or equipment?

Yes, ash anthracnose can spread via wet hands, pruning tools, and even clothing.

What role does climate play in the prevalence of Ash Anthracnose?

Wet weather is a breeding ground for most fungi, including ash anthracnose.

Shade trees provide both beauty and purpose for your property in Denver, and with so many different types of shade trees, it’s exciting to pick the right ones to plant in your soil. In this blog, we’ll discuss how shade trees can benefit your property, and what types grow best in our Colorado climate.

The Benefits of planting shade trees in Denver

Shade trees offer a number of benefits to humans, animals, and the surrounding environment. They’re large, and their canopies stretch across your yard, providing a home for all different types of animals throughout the year. They’re also great at keeping wind and rain at bay, so you can enjoy shelter underneath. Best of all, shade trees have been proven to cool the air that’s directly underneath their canopies by up to 25 degrees. If you plant shade trees over your home, you can enjoy energy savings throughout the hot, summer months.

Factors to Consider Before Choosing Shade Trees

When purchasing shade trees for your yard, you’ll want to consider these factors:

1. The Denver climate
2. Your soil and site conditions
3. Maintenance requirements

Select trees that can handle Denver’s high altitude, dry climate, and alkaline soil. Have your soil tested before you buy any trees, since yours may be different, and may need to be amended to give your tree a good start. It’s also important to research each type of tree so you know how much water, fertilizer, and attention it needs throughout the year. 

Deciduous Shade Trees

Deciduous trees shed their leaves in the fall. They’re best known for their brightly colored yellow, orange, and red leaves in autumn and new growth that occurs in the spring. There are several different types of deciduous shade trees that grow well in Denver.

Maple Trees

Autumn blaze and Norway maple trees are large deciduous trees that look lovely in home landscapes. Sugar maple trees sport an explosion of red, orange, and yellow colors in the fall before shedding their leaves, and silver maple trees can be identified by their beautiful silver-toned bark.

Oak Trees

Oak trees are solid, hardy, and massively beautiful. Their canopies will stretch far and wide to shade your entire lawn. Some great oak tree varieties include the northern red oak and the bur oak tree. Oak trees also grow as quickly as maple trees do here in Colorado.

Other Deciduous Shade Trees

The honeylocust and linden trees are also beautiful trees that provide plenty of shade. Honeylocusts offer filtered light through their small leaves, and linden trees grow tiny white flowers that attract bees and hummingbirds. Spring snow crabapples, Japanese tree lilac and other non-fruit bearing trees make good options as well. 

Evergreen Shade Trees 

Evergreen trees are known for their foliage that remains green all year. These trees require full sun.

Pine Trees

Pine trees like the Austrian pine and the ponderosa pine are low-maintenance shade trees that provide plenty of protection from the wind. Pine trees also provide privacy for your home. 

Spruce Trees

Colorado spruce and Engelmann spruce trees grow tall, and they’re excellent at providing a wall of protection from the wind and sun in your yard. 

Fir Trees

Fir trees prefer full sun and offer excellent shade for your home and property. Make sure you research how to keep them healthy, since they’re prone to root diseases and damage if exposed to cold temperatures and soil that is too alkaline.

Two other types of evergreen shade trees include junipers and cedar trees.

Native Shade Trees of Denver

Native trees grow best in Denver because they’ve grown accustomed to our climate, soil, and altitude. Some native shade trees include:

• Rocky Mountain Juniper
• Plains Cottonwood
• Narrowleaf Cottonwood

Fast-Growing Shade Trees for Immediate Relief

If you want to plant shade trees that grow quickly, consider these fast-growing trees. With proper care, they’ll grow very quickly, so you can bask in their shade without having to wait years or even decades. They include:

• Hybrid Poplar
• Weeping Willow
• Maples, Oaks, and Pear Trees

Best Shade Trees for Small Spaces

If you want to plant a shade tree, but you’re cramped for space, consider these petite varieties:

• Amur Maple
• Japanese Tree Lilac
• Hot Wings Maple
• Hornbeams 
• Skyrocket Juniper
• Spearmint Juniper

Successfully Plant and Grow Shade Trees in Your Yard with American Arbor Care

If you’re on the hunt for the perfect shade trees for your yard, contact us today. Our experts will be happy to help you find the right trees for your space.

Oak trees are known for being solid, strong and dependable, but they’re still susceptible to certain diseases. Oak leaf blister is one that needs to be understood, so you can mitigate the problem as soon as it appears.

Understanding Oak Leaf Blister

Also known as oak leaf curl, oak leaf blister is a fungal disease that causes raised areas on the leaves of oak trees. Red oak trees are especially susceptible to the disease, but most oak trees are vulnerable. If a tree is infected with oak leaf blister and the environment is right, it may lose its leaves before fall arrives. 

Identifying Oak Leaf Blister

Oak leaf blister appears as blister-like raised or depressed spots on the tops of leaves. The bottom of the leaves may turn gray, while the tops of the blisters may turn yellow and eventually, brown. The fungus usually only affects young leaves.

Causes and Contributing Factors

Oak leaf blister is a fungal disease. Spores spread in mid-spring through the wind and splashing raindrops onto buds and twigs. The fungus remains dormant until the following spring when cool, wet weather allows spores to germinate and the fungus to spread.

Impact on Oak Trees and Prevention Strategies

Although unsightly, oak leaf blister usually does not impact the health of the tree. Mature leaves are not generally susceptible to the fungus, and once young leaves fall, the tree can continue to grow healthy and strong.

Water your tree frequently, especially during seasons of drought. Fertilize appropriately and prune when needed. A healthy oak tree is far less susceptible to diseases and infestations.

Early Detection Techniques and Treatment Options

Oak leaf blister is easy to spot in the springtime as new leaves begin to grow. The large blisters may look alarming, but affected leaves will soon fall and the tree will be just fine. In cases where leaf drop occurs early in the season, your oak tree may grow new foliage before autumn begins.

Treatment options include regular tree maintenance and close observation. If necessary, your arborist may choose to apply a fungicide to the tree in the spring, when the buds are beginning to develop.

Hiring Professional Help

Professional arborists are tree experts who know how to identify and treat a variety of fungal diseases and infestations. If your trees seem weak or unhealthy, it’s always best to consult the pros. We can identify the problem and treat it quickly to avoid further deterioration of the tree and avoid the spread of disease. If you’d like to learn more about common tree disease or you’d like to schedule an inspection, contact us at American Arbor Care today.

Frequently Asked Questions (FAQs)

What causes Oak Leaf Blister?

Oak leaf blister is caused by the fungus Taphrina caerulescens.

How can I identify Oak Leaf Blister on my Oak tree?

Oak leaf blister is easy to spot by the raised and depressed spots on young leaves that develop in early spring. 

Are all Oak trees susceptible to Oak Leaf Blister?

Yes, all oak trees are susceptible to the disease, and red oak trees are especially vulnerable to this fungus.

What is the best time to apply fungicides for Oak Leaf Blister?

The best time to apply fungicides for oak leaf blister is in the early spring, as buds begin to appear.

Can Oak Leaf Blister be treated without chemicals?

Yes, oak leaf blister can typically run its course without the need for fungicides, but not always. In severe cases, a fungicide may be necessary to protect the tree.

Are there preventive measures to avoid Oak Leaf Blister?

The best way to prevent oak leaf blister is by keeping your tree in good health. Water it frequently, apply fertilizer as needed, and prune away dead branches when necessary.

What should I do if my Oak tree is already severely affected?

Call your local arborist. They’ll be able to address the problem quickly to save your tree.

Are there signs of resistance in certain Oak varieties?

Mature leaves are resistant to oak leaf blister, but all oak trees are vulnerable to the disease.

How often should I inspect my Oak trees for symptoms?

Check your oak trees in early spring, as new leaves begin to grow.

Can Oak Leaf Blister spread to other trees in the vicinity?

Yes, oak leaf blister can spread through raindrops and wind.

Are there community initiatives for Oak tree health?

There are plenty of initiatives for tree health. Your local arborist can provide you with the best resources.