Four Diseases That Damage Trees Extensively Along The West Coast

Posted on: 19 July 2017

Whether you have one tree in your yard or a whole forest of them, it's important to keep an eye on their health. Many tree diseases are spread easily from tree to tree if you don't eradicate the infected trees quickly. Other times, you may actually be able to help the tree recover if you detect and treat the disease early on. There are hundreds -- perhaps thousands -- of tree diseases. However, the following four are some of the most common ones to watch out for when you live on the west coast.

Bacterial Leaf Scorch

Bacterial leaf scorch is one of a few tree diseases that are caused by bacteria, rather than by fungi. It can affect almost any type of deciduous tree, and it also appears in shrubs and pepper plants. The primary symptom of the disease is browning of the leaf along its primary veins. The symptoms usually appear at the crown of the tree first, and they slowly spread downward. Eventually, the tree succumbs to the infection.

There's no effective treatment for bacterial leaf scorch. However, it is easily spread from tree to tree by insects known as leaf hoppers. If your trees are showings signs of bacterial leaf scorch, have a tree service expert come examine them -- and if they diagnose the tree, have them remove it promptly before your other trees become infected, too.

Dutch Elm Disease

You really only need to be concerned about this disease if you have elm trees. It's a fungal infection that causes the foliage to brown and fall to the ground prematurely -- first on one branch or side of the tree, and eventually across the entire tree. Then, the branches develop dark streaks. 

There is no effective treatment for a tree once it is infected with Dutch Elm Disease, but there are a few steps you can take to protect your trees. Have them sprayed with insecticide each spring. This will ward off the Elm Bark Beetles that spread the disease from tree to tree. Also, avoid bringing elm firewood onto your property, as it may be harboring some beetles.


Anthracnose is a common fungal tree disease that is found across the country, but is particularly common on the west coast due to the moist, humid weather. It typically appears in the spring, causing uneven, jagged-edged black spots to appear on leaves. The spots them become pink and bulbous as the fungi create spores -- but the leaves do not fall to the ground prematurely as with some other tree diseases.

Anthracnose is easier to treat than most other tree diseases. Have a tree care company come spray your tree with fungicides. They should repeat this treatment the next spring. With any luck, the leaves should emerge free of fungus the next season.

Needle Cast

Evergreen trees, from sugar pines to ponderosa pines, dot the west coast. When these trees' needles begun to develop yellow and brown spots along with tiny black dots along their length, this indicates that the tree has become infected with needle cast. Needle cast is a fungal infection that only affects evergreen species. If left untreated, the affected branches may die entirely. It is rare for the condition to completely kill a tree, but badly infected trees may end up with several dead branches.

To get a needle cast infection under control, you'll need to work to reduce your trees' stress levels. Apply water to the ground around the tree when rain is scarce, and scatter mulch around the tree to trap moisture in the soil for longer. The mulch will also slowly break down, adding nutrients back to the soil for the tree to use. With any luck, the tree's health will become more robust, and it will fight off the infection within a year or two.

If you keep your eyes out for the diseases above, you'll be well on your way to better landscape care on the west coast. Check out sites like for more information.