How Do You Treat An Arborvitae Fungus

You treat an arborvitae fungus by first correctly identifying the problem and then applying a combination of pruning, fungicides, and better cultural care.
 
An arborvitae fungus usually shows up as browning needles, yellowing branches, or black spots on the foliage.
 
If you catch it early, treating an arborvitae fungus is very doable and your tree can bounce back strong.
 
In this post we’ll walk through how to spot an arborvitae fungus, the best ways to treat an arborvitae fungus, and how to keep it from coming back.
 
Let’s dig in and save those beautiful evergreens.
 

How to Identify Arborvitae Fungus

The first step in learning how do you treat an arborvitae fungus is knowing exactly what you’re dealing with.
 
An arborvitae fungus can look like several different things and mistaking it for winter burn or insect damage leads to the wrong treatment.
 
Here are the most common signs of an arborvitae fungus:
 

1. Brown or Yellow Needles That Don’t Green Up

When an arborvitae fungus attacks, the foliage starts turning brown or yellow from the inside out.
 
This usually begins on the lower branches or in the middle of the plant where air circulation is poor.
 
If you see browning that isn’t caused by drought or wind, suspect an arborvitae fungus.
 

2. Black Spots or Powdery Growth on Leaves

Two common fungi that plague arborvitae are shot hole disease and tip blight.
 
Shot hole disease creates tiny black spots that later fall out, leaving little holes in the needles.
 
Another arborvitae fungus called powdery mildew leaves a white or gray dusty coating on the foliage.
 

3. Cankers and Dieback on Branches

A more aggressive arborvitae fungus like Phomopsis or Kabatina causes sunken, discolored cankers on stems.
 
Branches above the canker turn brown and die back, often in a scattered pattern throughout the tree.
 
If you scrape the bark and see dark, oozing tissue, you’re dealing with an active arborvitae fungus.
 

How to Treat Arborvitae Fungus Step by Step

Now that you know what you’re fighting, let’s answer the main question: how do you treat an arborvitae fungus?
 
The approach depends on how advanced the infection is, but these methods work for almost every arborvitae fungus.
 

1. Prune Out Infected Branches Immediately

The first thing you do to treat an arborvitae fungus is remove all diseased wood.
 
Cut branches back to healthy green tissue, and clean your pruners between cuts with rubbing alcohol.
 
Throw the infected clippings in the trash — never in your compost pile — because the arborvitae fungus can survive there and reinfect your plants.
 

2. Apply a Fungicide Labeled for Arborvitae Fungus

For moderate to severe cases, a chemical treatment is the most reliable way to treat an arborvitae fungus.
 
Look for fungicides containing copper, chlorothalonil, or mancozeb.
 
Spray every 7–14 days during wet weather, covering all foliage thoroughly including the undersides of needles.
 
Always follow the label directions because overapplying a fungicide can damage an arborvitae’s sensitive foliage.
 

3. Improve Air Circulation and Sunlight Exposure

An arborvitae fungus thrives in damp, shady, crowded conditions.
 
After treatment, thin out nearby plants or prune overlapping branches so light and air can reach the inner foliage.
 
If your arborvitae is planted too close to a wall or fence, consider transplanting it to a more open spot.
 
Better airflow is one of the most effective long-term answers to how do you treat an arborvitae fungus.
 

Preventing Arborvitae Fungus From Coming Back

Even after you successfully treat an arborvitae fungus, the spores can linger in the soil and debris.
 
Here’s how to keep another arborvitae fungus from striking:
 

1. Water at the Base, Not Overhead

Wet foliage is the number one invitation for an arborvitae fungus.
 
Use a soaker hose or drip irrigation to water the roots directly and keep the needles dry.
 
If you must use a sprinkler, do it early in the morning so the sun dries the leaves by midday.
 

2. Rake Up and Remove All Fallen Debris

Spent needles, dead leaves, and fallen twigs can harbor an arborvitae fungus over winter.
 
Clean up around the base of your arborvitae in both fall and spring.
 
A layer of fresh mulch is fine, but keep it a few inches away from the trunk to avoid moisture buildup.
 

3. Space New Arborvitae Plantings Properly

When planting new Arborvitaes, give them room to grow without touching each other.
 
Crowded plants trap humidity and create the perfect environment for an arborvitae fungus to spread.
 
Follow the mature width recommendation for your variety — usually 4 to 6 feet apart for most hedge types.
 

So, How Do You Treat an Arborvitae Fungus?

You treat an arborvitae fungus by correctly identifying the symptoms, pruning off infected tissue, applying the right fungicide, and improving growing conditions.
 
An arborvitae fungus is not a death sentence if you catch it early and use a combination of these methods.
 
Focus on prevention after treatment, and your evergreen hedge or tree will stay healthy for years.
 
Hope this guide gave you a clear answer to how do you treat an arborvitae fungus.
 
Now go give your arborvitae the care it deserves.