Homeowners in the Portland area should know as much as possible about common diseases that can infect and destroy Pacific Northwest trees. A tree that’s infected by one of these diseases can be a gateway to pests and bugs and spread to other trees on your property. Here are some of the most common and dangerous diseases that affect Pacific Northwest trees that a top-of-the-line tree professional like Mr. Tree can help you manage.
- Phytophthora Root Rot
Phytophthora root rot is generally caused by overwatering the soil around the tree or subpar drainage. The tree becomes unable to receive the nourishment and moisture necessary from the soil, and as a result, the roots are deprived of oxygen and slowly decay and die out. The process can take years, and the tree may suffer for a very long period before it dies, or it can be quick, and the tree can die within one season. To prevent root rot, ensure good soil drainage, create irrigation moats to keep water from pooling against the trunk, and avoid overwatering at all costs.
How do you know if your tree has root rot? Several key indicators may be present, including a thinning canopy, poor growth, unhealthy appearance, small and pale leaves, yellow or wilted leaves, and branch dieback. If you want to know for sure whether root rot is the cause of the problems with one of your Pacific Northwest trees, an arborist will need to look several inches below the soil line by carefully removing a small amount of outer bark tissue. The arborist will look for discoloration among the inner wood, as well as a foul smell and black dead tissue.
What should you do if one of your Pacific Northwest trees does have root rot? If your tree has advanced root rot, it’s likely too far gone, and you’re better off removing it outright. However, if the tree only has moderately serious root rot, you may be able to save it if you hire a professional arborist to carefully prune out the infected roots.
Anthracnose is a fungal disease that infects shade trees and causes cupping or curling of leaves, early leaf drop, or leaf spots. The most common way for a tree to catch this disease is if strong wind and rain hit it in the spring following a mild winter, so this is a common problem for Pacific Northwest trees. The good news is, while anthracnose can reduce growth and make a tree’s appearance far less pleasant, it is unlikely to outright kill a tree.
Typically, the best defense against the disease is to keep your tree as healthy as possible all year by providing it with proper amounts of fertilizer and water, getting your tree inspected every few years, and having the tree pruned by a professional.
How do you know if your tree has anthracnose? The symptoms are usually relatively easy to notice, such as cupped, distorted, or curled leaves; minor insect feeding wounds; brown and irregularly shaped spots; and leaves that appear to be predominantly affected on the inner and lower branches of the tree.
If you suspect one of your trees has anthracnose, immediately get rid of fallen twigs and leaves from around the tree and the yard, which should reduce the following year’s outbreak potential. A professional pruner should get rid of dead branches and twigs at the crown of the tree so that there can be better airflow into the canopy. If the case of anthracnose is particularly serious, you may need to use a fungicide.
- Verticillium Wilt
Verticillium wilt is a serious fungal disease that lives in soil and gets into the tree through the roots. It spreads through the branches and plugs up the cells, resulting in water not being able to reach the leaves. The best way to prevent verticillium wilt is to always keep the tree healthy by pruning dead branches regularly, since usually only trees that are already sick or damaged will catch the disease.
How do you know if your tree has verticillium wilt? Typical warning signs include yellow-green streaks, a decline in twig growth, an increase in dead branches, discolored sapwood, and branches that wilt on the sides of the tree.
Unfortunately, there’s no cure for this disease, so your only recourse is to hire a professional arborist to help you preserve it for a few extra years before it eventually dies or to have it removed so it doesn’t spread to the other trees on your property.
- Bronze Birch Borer/Emerald Ash Borer
Two types of beetles that are common in Pacific Northwest trees are the bronze birch borer and the emerald ash borer. They can cause severe or even deadly damage by boring into the wood of a tree and eating its interior tissue, as well as its leaves and foliage. Truthfully, it’s very difficult to guard against these destructive beetles. The best way to prevent an infestation is by properly caring for your trees all year and possibly using preventative chemical treatments. Speak with an arborist to explore your options.
Typical warning signs of borer beetles include holes in the bark, larvae feeding beneath the bark, and yellowing leaves at the bottom of the tree.
What can you do if one of your Pacific Northwest trees infested? Unfortunately, once the tree is infected, it cannot be saved, so you should remove it immediately to stop the beetles from spreading to other trees on your property.
- Thousand Cankers Disease
Thousand cankers disease is caused by a fungus that’s transmitted by adult bark beetles, and it causes cankers to develop in the inner bark of a tree, disrupting the flow of nutrients to the tree. Unfortunately, this disease spreads rapidly, and once a tree is infected, it can’t survive, so it’s best to remove an infected tree immediately to stop the disease from spreading to other trees on your property.