Aspen Trees

Resources to Help You Care for Colorado’s Favorite Tree

Aspen trees seem to be almost everywhere in Colorado. But, despite their popularity, aspens can be finicky trees to grow. Not only do they require very specific growing conditions, they’re also prone to a wide range of insect and disease problems.

On this page, we share some resources to help you identify what may be wrong with your aspen tree, understand what it needs to thrive in your yard, how to handle aspen problems, and some suggested alternatives that will bring a similar look and feel to your property.

Aspen Problems?

Send us an email describing the problem(s) your tree is experiencing. Please include one or two images showing the issues.

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Signs & Symptoms of Aspen Tree Problems

Hover on the photos to learn more about the causes and treatment for common aspen pests and diseases in the Denver Front Range area.

Poplar Borer

Poplar Borer

What is it? Poplar borerSymptoms: This beetle makes holes in the bark. You may see pieces of wood around the hole and below it on the ground. Sometimes the holes leak a brown resin (aspen sap) that runs down the trunk.Treatment: Wrap a wide strip of flexible paper around the trunk and coat it with a sticky barrier to trap insect larvae, or treat with an insecticide. Soil injections available, contact us for more information.

Spider mite damage

Spider mite damage

What is it? Spider mite damage Symptoms: Light colored dots or flecks, scorched edgesTreatment: Water plants regularly, spray leaves with jet of water. Lam has an injected treatment that lasts 30 to 45 daysLearn more in our article about spider mites 

Aphids

Aphids

What is it? Aphids Symptoms: Sticky substance (honeydew) or a grey, powdery coating (sooty mold), curling leaves, large number of waspsTreatment: Natural predators, spray off with water, early-season treatment (before bud break, usually April or early May) with a soil injection containing a system insecticide. Summer treatment involves a foliar spray.

Cytospora canker

Cytospora canker 

What is it? Cytospora canker Symptoms: Tree turning orange, sometimes over an entire branch, may ooze brown liquidTreatment: Keep trees well-watered and pruned and repair any wounds. Remove infected branches or infected bark and prune only in dry weather. Contact LAM Tree if you suspect cytospora canker on any of your trees.

Cytospora spore tendrils

Cytospora spore tendrils

What is it? Cytospora spore tendrilsSymptoms: Tree turning orange, sometimes over an entire branch, may ooze brown liquidTreatment: Keep trees well-watered and pruned and repair any wounds. Remove infected branches or infected bark and prune only in dry weather. Contact LAM Tree if you suspect cytospora spore tendrils on any of your trees.

Oystershell scale

Oystershell scale 

What is it? Oystershell scale Symptoms: Brown or gray scale shaped roughly like an oyster’s shell.Treatment: Must be treated with a systemic insecticide before the eggs hatch, usually in late May or early June.

Sapsucker Damage

Sapsucker Damage

What is it? Damage from a Sapsucker (member of the woodpecker family)Symptoms: ¼ inch holes in neat rows in trees as the sapsuckers search for food (bugs or tree sap)Treatment: Wrap trees in burlap or hardware cloth to prevent sapsuckers from feeding, may need to treat any underlying disease or pest infestation. Silver streamers (like ribbon) can be thumb-tacked to tree to deter sapsuckers.Treatment timing: Will need to remove and redo the cloth as the tree growsNotes: The tree will die if it becomes covered (girdled) with these holes

Aspen Tree Resources

Instead of Aspens, Plant These 7 Trees for Fall Color

Love the look of aspen trees but not happy with how finicky they are to grow? Try one of these seven easy-care trees with great fall color! Read More →

Aspens Turning Orange? It’s Cytospora Canker

Cytospora canker causes dead or dying areas on tree bark. In aspens, this area turns orange. The cankers kill tree branches (you’ll often see this in spruce) and, in severe cases, will kill the whole tree. There’s no cure so prevention is critical. Read More →

Aspen Trees: Common Problems & What To Do

Although Colorado’s aspen trees are beautiful, they’re also prone to a host of aspen tree problems. Thankfully, most are preventable or treatable – especially if you address the #1 issue nearly all aspens in our area face. Read More →

Aspen Leaf Blight: Symptoms & Solutions

Aspens are prone to fungal foliage diseases (aspen leaf blight). Severe outbreaks cause premature defoliation or dieback of parts of the tree and, depending on when the outbreak occurs, can even kill the tree. Read More →

Aspen (Populus tremuloides)

This iconic tree, native to Colorado, has gorgeous yellow fall foliage but is one of the more difficult trees to grow in your home landscape. Read More →