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Denver Tree Service Shares Common Pests to Watch for This Spring

February 7, 2018

Spring is just around the corner and before you know it, your trees will start blooming like mad. While their leaves and blossoms offer plenty of shade and beauty for your landscaping, they can be damaged relatively easily. After a long winter, pests, diseases, and fungi all start getting active and these hazards can quickly turn the foliage from green to brown. Once the damage starts, correcting the issue can be difficult at best, but the sooner you notice anything amiss, the better. Here are a few of the most common issues Denver landscaping companies see in trees during the spring.

Scale Insects

Scale insects are a lot like the aphids you see on flower bushes and in houseplants, but they prefer trees. These little green insects eat through the leaves and buds of trees entering their main growing season, leaving small holes and slimy trails behind. In addition to sticky and slimy leaves, scale insects also deposit harmful a harmful fungus on the bark and leaves which can spread to the rest of the tree if left unchecked.

Unlike aphids, scale insects are much easier to see often before the infestation reaches extreme levels. Look for colorful patches on the trunk and in the branches as scale insects like to gather in groups. If you notice a large number of insects, don’t panic—there may not be a full infestation. However, you will want to schedule an inspection with an arborist to assess the damage and develop a treatment plan. The longer these insects stay in the tree, the more likely it is that the tree will rapidly deteriorate.


Though more commonly associated with roses and other flowering bushes, aphids have been known to make a home in the trees. Like scale insects, they eat the leaves and blossoms on your trees and leave behind a sticky sap-like substance after digesting the plant material. Once the leaves become coated in the substance, they start to wither and decay. Over time, the decay can result in trunk mold and lead to severe damage to the tree’s vascular system.

Surprisingly, there are many different types of aphids that can infest trees, and since they’re small and difficult to see, identifying them can be difficult. Once you recognize the symptoms as an aphid infestation, you’ll need to have the condition assessed to better develop a treatment plan. Different species of aphids respond to different pesticides, and using a generic treatment may not be enough to get rid of the infestation.

Bark Beetle

Bark beetles have been a problem for the last decade, especially among Colorado’s pine and juniper population. These insects burrow into the trunk and slowly eat away at the wood, killing the tree’s circulatory system. Damage often starts to manifest as discolored needles, typically beginning at the top of the tree. However, unlike other pests, bark beetle damage cannot be repaired once an infestation is found. Instead, you’ll need to remove the infested tree from the property and either spray the tree with a chemical treatment or burn the wood. Luckily, removing the tree is often enough to prevent the spread of beetles on your property. If you’ve noticed bark beetle damage on nearby properties, you may want to use preventative treatments and sprays to protect the pines in your yard.


While termites are more commonly associated with structural damage to buildings, they can also wreak havoc on your home’s landscaping. When left unchecked and untreated, termites can slowly kill the tree, eating away at the cellulose inside the wood and weakening the supportive structure of the trunk and roots. Termite damage is relatively easy to spot even in the early stages of an infestation. Look around the trunk of the tree. If you see wood dust mixed with the dirt or notice mud tubes climbing the base of the tree, there may be termites nearby. Take a stick or shovel and gently dig up a small amount of soil around the tree. If termites are infesting the tree, they’ll likely be crawling in the soil. Though they spread slowly, you’ll still want to schedule treatment as soon as possible. Putting off a termite extermination not only puts the rest of your landscaping at risk, but also increases the likelihood of a colony taking up residence in your house.

Emerald Ash Borer

The emerald ash borer is a relatively new addition to Colorado’s pest list, with the first known infestation being detected in 2013. These troublesome pests do most of their damage in the larval state when they burrow into the trunk, consuming the wood pulp and cellulose of the trunk. When a large enough population of borers takes up residence in a tree, it can compromise the health of the tree, killing it slowly from the inside. The easiest way to prevent damage from emerald ash borers is to make sure the trees are properly cared for and can firmly establish themselves in your yard. Most severe damage only happens when the trees do not have an established root system or have experienced other infestations that compromise their health.

Root Rot

Though not an insect, root rot can be just as deadly even for otherwise healthy trees. This condition is most common during the spring and is caused by moist wet soil that does not have adequate drainage. Soil naturally traps moisture and water around the roots of living trees, helping them receive the nutrients they need. However, when the water can’t evaporate, it can cause the material to break down while also encouraging mold and fungus growth in the soil. Often, the fungus will spread throughout the root system, preventing the roots from getting the nutrients they need to thrive.

While it can occur in yards with poorly timed irrigation systems, it can also result from natural weather patterns like frequent heavy rain or slow snowmelt. If the ground seems saturated, avoid watering the area until the first few inches of soil dry out. The last thing you’ll want to do is add water to the soil. Unfortunately, root rot can only be prevented rather than cured. Work with a landscaping team to ensure that your space has the proper drainage to keep moisture from being a problem.

Whether you think you have a pest problem or simply want to set your trees up for a successful growing season our crew is ready to help. At Arbor Garden, we believe that every homeowner deserves a beautiful yard filled with healthy trees. Contact us today and let our team keep your trees happy, healthy, and thriving.