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Treating arborvitae diseases requires a combination of proper identification, cultural adjustments, and occasionally chemical treatments.
If you’ve noticed your arborvitae turning brown, losing needles, or oozing sap, you’re likely dealing with a disease that needs attention.
The good news is that knowing how to treat arborvitae diseases early can save your hedge and prevent the problem from spreading.
In this post, we’ll walk through exactly how to treat arborvitae diseases, from spotting the symptoms to choosing the right solution.
Let’s dig in and get your evergreens healthy again.
How to Treat Arborvitae Diseases: Start with Identification
Before you can treat arborvitae diseases effectively, you need to know what you’re up against.
Different diseases require different approaches, so misidentifying the problem can waste time and money.
1. Needle Blight (Pestalotiopsis)
Brown or bronze tips on your arborvitae, especially in late spring or summer, often point to needle blight.
This fungal disease attacks the tips first, causing dieback that moves inward if left unchecked.
To treat arvitae diseases like needle blight, prune affected branches at least 6 inches below the brown tissue.
Dispose of the infected clippings in the trash, not your compost pile, to stop spores from spreading.
2. Canker Diseases
Sunken, cracked areas on the bark—often with oozing resin—signal a canker infection.
These fungal or bacterial infections girdle branches, cutting off water flow and causing dieback.
How to treat arborvitae diseases from canker involves cutting out the cankered branch well below the infected section.
Sterilize your pruning tools between cuts with a 10% bleach solution to avoid transferring the pathogen.
3. Root Rot (Phytophthora)
Yellowing, wilting foliage and stunted growth, even when soil is moist, suggest root rot.
This soil-borne disease thrives in waterlogged conditions and is often fatal if not caught quickly.
Treating arborvitae diseases like root rot requires improving drainage immediately and may involve fungicide drenches.
If the plant is severely affected, remove it entirely and avoid replanting arborvitae in the same spot.
How to Treat Arborvitae Diseases with Cultural Care
The most effective way to treat arborvitae diseases is to create an environment where diseases can’t thrive.
Healthy plants resist infection better, and good cultural practices are your first line of defense.
1. Water Correctly
Water at the base of the plant, not overhead, to keep foliage dry and reduce fungal spores.
Arborvitae diseases like blight and canker flourish in wet leaves, so water early in the day so the plant dries by nightfall.
Deep, infrequent watering encourages deep root growth, making your arborvitae more resilient.
2. Prune for Airflow
Dense, crowded foliage traps moisture and creates a perfect breeding ground for disease.
Thin out inner branches and remove any dead or crossing limbs to improve air circulation.
Good airflow is a simple but powerful way to treat arborvitae diseases without chemicals.
3. Mulch and Feed Smartly
Apply a 2-inch layer of organic mulch around the base, but keep it away from the trunk to prevent rot.
Use a slow-release fertilizer formulated for evergreens in early spring to support vigorous growth.
Healthy arborvitae resist arborvitae diseases better than stressed plants, but avoid over-fertilizing, which can encourage lush, soft growth that’s more susceptible to infection.
How to Treat Arborvitae Diseases with Fungicides and Chemicals
Sometimes cultural care isn’t enough, and you need a targeted chemical approach to treat arborvitae diseases.
Always read and follow label instructions precisely, and apply only when conditions favor disease development.
1. When to Use Fungicides
Apply fungicides preventatively in early spring before new growth emerges, especially if you’ve had trouble with blight in the past.
For active infections of how to treat arborvitae diseases, pruning out infected parts first, then spray the remaining foliage with a copper-based or chlorothalonil fungicide.
Reapply every 7–14 days, or after heavy rain, until symptoms stop spreading.
2. For Root Rot
Fungicides containing mefenoxam or phosphonate can help manage root rot if caught early.
Drench the soil around the root zone according to the product directions, repeating as needed each season.
Keep in mind that chemical treatments alone often won’t cure advanced root rot—you must also fix drainage issues.
3. Safety Precautions
Wear gloves, long sleeves, and a mask when applying any chemical for treating arborvitae diseases.
Avoid spraying on windy days to prevent drift, and never apply when rain is expected within a few hours.
Store chemicals out of reach of children and pets, and dispose of containers responsibly.
When to Call a Professional for Arborvitae Disease Treatment
Some situations are too severe for DIY treatment when you’re learning how to treat arborvitae diseases.
A certified arborist can diagnose the exact pathogen, prescribe the right treatment, and apply it safely.
1. Large or Mature Hedges
If your arborvitae hedge is tall or extensive, reaching infected upper branches may be dangerous or impossible.
Professionals have the equipment to prune and treat tall plants without injury.
2. Recurring or Spreading Diseases
If the same arborvitae diseases keep coming back despite your best cultural and chemical efforts, you need expert insight.
An arborist can test soil and tissue samples to identify underlying issues like soil compaction or nutrient imbalances.
3. Large-Scale Dieback
When whole sections of your arborvitae are dying rapidly, professional intervention is critical to save the rest.
They can treat arborvitae diseases with trunk injections or high-volume sprays that aren’t available to homeowners.
So, How to Treat Arborvitae Diseases?
Treating arborvitae diseases starts with accurate identification and then combines proper pruning, good watering habits, improved airflow, and, when necessary, targeted fungicides.
The earlier you catch the problem and begin to treat arborvitae diseases, the better your chances of saving your plants.
Always monitor your arborvitae regularly for any signs of trouble and act quickly when you see them.
With patience and the right approach, you can restore your hedge to its lush, green glory and keep it healthy for years to come.
Happy growing.