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5 Tree Diseases to Watch Out for in the Pacific Northwest

The Pacific Northwest provides the perfect environment in which many trees can thrive. Despite the pleasant conditions, however, trees in this area are still susceptible to some tree diseases. Tree diseases can hit at any time and can be present in trees while showing minimal to no symptoms. If you’re not a tree expert, it can be hard to notice if something isn’t right with your tree before it’s too late.

Tree disease is something that can happen without much notice and can prove to be fatal for the trees on your property. While some tree diseases can be prevented, others quickly take on a life of their own. When this happens, the best thing you can do is be aware of the symptoms and enlist the help of professionals like Mr. Tree as soon as possible. Here are a few of the tree diseases you should be aware of in the Pacific Northwest.

1. Root Rot

The ample precipitation in the Pacific Northwest can be a welcome benefit for many trees, but it can also leave them more susceptible to tree diseases such as root rot. The roots of a tree play a big role in its overall health, making root rot one of the more detrimental diseases that can affect your tree. The effects can weaken the base of your tree, making it more prone to potentially falling over and causing damage to your property.

Root rot disease is caused by insufficient drainage to the area around the roots. The pooling water around the base of the tree makes it harder to absorb nutrients, as it starves the tree of oxygen. Over time, the excess water will begin to rot the roots, making them weaker and allowing them to loosen their grip on the soil.

Identifying root rot can be difficult, as it may take a few seasons for symptoms to begin to show, despite the diseases being present for years. Some symptoms to keep watch for are drought-stressed leaves and darker bark around the soil line.

2. Dwarf Mistletoe


Dwarf Mistletoe

Dwarf mistletoe is a tree disease that’s known to affect trees like Douglas firs, pines, and fruit trees. All of these trees are quite popular in the Pacific Northwest, which is why it’s a good idea to be able to spot and identify dwarf mistletoes should they be present on your trees.

This tree disease is a small parasitic plant that grows roots in the stem of its host tree and deprives the tree of nutrients it needs to survive. They grow in clusters of yellowish-green plants. They are known to spread out and cause witches’ brooms, which can create the perfect ladder for fires to quickly find their way to the crown of a tree.

Though it may seem easy to simply cut off the affected areas, dwarf mistletoe is known to spread quickly to surrounding trees. Once you become aware of it on one tree, you’ll likely begin to see it on others in or around your property. It spreads by an explosive discharge of seeds that can disperse to host needles 10 to 50 feet away. Their presence may cause fruits of fruit trees or the bark at the site of the infection to swell.

3. Verticillium Wilt

Many tree diseases plant themselves onto the tree itself and infect it from there, but that isn’t the case when it comes to verticillium wilt. This tree disease is slightly different because it can be found in the soil surrounding the tree. It lives in the soil and infects your tree through its root system, making it a pretty tough disease to fight off.

Verticillium wilt penetrates the roots through natural openings, where it then can make its way through the branch system, further infecting the tree. Once the disease reaches the branches, it’s known to cause the cells of the tree to “plug” themselves, making it harder and harder for nutrients to flow through them. The branches soon become so plugged that water cannot freely move throughout the tree and reach the leaves.

Once verticillium wilt infiltrates your tree fully, you’ll soon start to see symptoms that will alert you to what’s occurring. One side of the tree may begin to wilt suddenly, or the leaves will suddenly change colors. The leaves may also change colors right before wilting. This tree disease can either kill the trees over a number of years or within a few weeks.

4. Sudden Oak Death

Sudden oak death has quickly made itself known throughout the states of Oregon and Washington. It’s a feral quarantined pathogen that’s known to have caused widespread dieback in species like tanoaks, wild rhododendrons, and evergreen huckleberry trees.

This disease moves fast, especially in tanoak trees, as they appear to die quite rapidly after being introduced to sudden oak death. One week the tree will appear to be normal, and the next it will be displaying green and brown leaves that are in the process of dying. Brown and black discolored patches may also be present on the bark of the lower trunk, where you may also find the presence of sap.

5. Anthracnose

The tree disease of anthracnose is often found on dogwood and maple trees in the Pacific Northwest and can also be found on other species of trees, including fruit trees. Anthracnose is a fungal disease that causes leaves to become disfigured by curling or spotting. The leaves will be the biggest sign that your tree is infected with this disease, as their appearance will change greatly and feature yellow spots in addition to disfiguration. In fruit trees, such as apple trees, anthracnose can produce cankers on the trees and cause rot on harvested fruits.

This disease and the ones listed before can often be treated by professional arborists. Pacific Northwest arborists like Mr. Tree can prune your tree back and get rid of infected leaves and branches. Fungicide treatment could also be used if it’s a problem that continually happens seasonally for your trees. In worst-case scenarios, professionals are capable of safely removing your diseased tree to prevent it from further damaging other trees on your property.