5 Common Tree Diseases & How To Protect Your Trees

Seeing brown spots on your tree’s leaves? A strange gelatinous mass that is reminiscent of something from a sci-fi flick? Your tree may be suffering from one of these five common diseases.

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Trying to identify what’s happening to your tree can leave homeowners confused and concerned. What is this? How did this happen? Will it hurt the tree? What are your treatment options? Contacting your local tree professional like Hansen’s Tree Service will help you diagnose the problem and offer treatment solutions. In the meantime, there are several ways you can care for your tree’s health. Preventive care is always best. Healthy and vigorous trees will defend themselves against most diseases.

Here’s a short list of some common tree diseases in our region:

Cedar Rusts

Cedar apple rust Gymnosporangium juniperi-virginianae fungus

Cedar rusts are a series of fungi that affect the leaves, fruit, and twigs of trees. They are unique as they require both cedar trees (Juniperus spp) and apple trees (Malus spp) to reproduce and survive. There are also other rusts that affect cedar and hawthorn. The cedar-apple rust produces brown colored galls on cedar twigs that rapidly grow gelatinous orange spikes after a spring rain.

Those spikes are the fruiting structure that produces spores that travel to apple trees and fall on the leaf surface causing brown spots. The brown spots on the apple trees produce spores that travel back to the cedar and trigger the growth of the brown galls on twigs. The cycle is repeated each year with each species creating spores that infect the alternate host plant. Properly timed fungicide applications can interrupt the cycle and prevent future infections.

Call your local tree care company like Hansen’s Tree to discuss preventive treatments that will help keep your trees healthy.

It is also a good idea to choose trees that are resistant to the fungus, as well as raking up and destroying infected leaves, and removing galls.


Anthracnose is a fungal disease that affects the leaves and stems of several tree species. Symptoms on sycamore are common nearly every spring, while dogwood, oaks, and maples can become infected during the wet and cool spring season.

Symptoms vary a bit between species, but are generally described as brown or black colored tissue on leaf surface or along veins. Uncontrolled, it can cause defoliation, and sometimes stem cankers that weaken stems and branches. .

This disease doesn’t kill the tree quickly but does reduce growth, makes it unsightly, and will create stress that eventually weakens and kills a tree. To help prevent anthracnose from developing, follow these maintenance steps:

  • Prune dead and dying branches to promote air circulation
  • Rake up and dispose of infected leaves to prevent new infections
  • Consult with a professional tree care service about a fungicide treatment. Treatments are best applied as preventive. They can be injected in the tree well in advance of the outbreak, or sprayed on to the leaf surface in multiple applications as the new leaves emerge in early spring. Once infected, trees will typically then show symptoms every spring.

Needle Diseases on Spruce

Needle browning on spruce trees can be caused by several issues, including a wide range of fungal diseases. As with many diseases, prevention is key. Proper fertilization and watering can help spruces remain vigorous and defend themselves against attack.

However, once symptoms appear, a series of fungicide treatments may be needed to prevent reinfection the following year.  Contact the tree professionals at Hansen’s Tree Service to ensure an accurate diagnosis and prescriptions to promote tree health.

Apple Scab

Apple scab is a disease that affects apple and crabapple trees, causing the fruit to develop tan, sunken spots, and the leaves of the tree to yellow and prematurely drop. Trees become infected in early spring as leaves develop.  An infected tree will flower normally and develop normal looking foliage.

But in July, the symptoms begin to appear as small measle-like spots and the leaf then yellows prematurely and falls off the tree. By late July and August, the tree appears weak and unsightly.

This disease is rarely lethal to your trees, but nevertheless it is essential that you maintain the tree and remove diseased limbs through professional pruning. Call your local tree care company like Hansen’s Tree to discuss preventive treatments that will help keep your trees healthy. You should also:

  • Rake up and destroy infected leaves
  • Apply a fungicide at a professional’s advice (typically springtime during leaf emergence)
  • Choose trees resistant to apple scab (many disease resistant cultivars are available)
  • Water properly during dry periods

Dutch Elm Disease

Dutch elm disease is a vascular wilt disease caused by a fungus. Infected trees will develop a clogged vascular system that restricts the flow of water and sugars in the tree. Once infected, your tree will experience symptoms like:

  • Yellowing, wilting, curling leaves
  • Leaf drops
  • Crown dieback
  • Brown discoloration on outer layer of wood under the bark

This disease is found in most of the U.S. and seriously and fatally affects American elms.

To manage the spread of Dutch Elm disease, maintain good tree health by consulting with your professional tree service like Hansen’s and following these tips:

Protect Your Trees! Call A Professional

To protect your trees from diseases like these, it is essential that you perform the proper care and maintenance year-round. Choose a professional, reputable tree care service like Hansen’s Tree Service that will consult with you about the best course of action.

If you wish to remove the diseased tree or seek further treatment, that decision is up to you. Our ISA Certified Arborists will clearly communicate with and educate you about different treatment methods to improve the health and safety of your trees.

Protect Your Tree’s Health!

Schedule Your HASSLE FREE Estimate Today!

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