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How To Treat Common Arborvitae Diseases – GIY Plants

Single green arborvitae growing in the front yard of a home.

Arborvitae, a popular choice for landscaping, is not just an ornamental shrub but also a sturdy evergreen that requires little maintenance. However, like all trees and shrubs, arborvitae are susceptible to various diseases affecting their health and appearance. This comprehensive guide aims to arm you with the knowledge and latest techniques to identify, prevent, and treat common arborvitae diseases, ensuring your green giants sustain their health and beauty.

What is Arborvitae?

Arborvitae, scientifically known as Thuja spp., is a coniferous evergreen widely used in landscaping. Known for its versatility and low maintenance requirements, arborvitae serves multiple purposes, from acting as a privacy screen to enhancing the aesthetics of gardens. However, despite its resilience, this tree is not immune to diseases. Understanding what arborvitae is and its common uses can help you better manage its health and tackle any disease problems that may arise.

Common Diseases Affecting Arborvitae

Arborvitae with a disease turning the tips of foliage brown.

Arborvitae trees can fall victim to various diseases, each with its own symptoms and signs. The most prevalent issues include:

  • Twig Blight: Caused by fungal pathogens, this disease leads to brown, wilted twig tips.
  • Root Rot: Poor drainage conditions can lead to this disease, causing the roots to rot and the foliage to turn yellow.
  • Arborvitae Needle Blight: This fungal disease affects the needles, causing them to turn brown and eventually leading to branch dieback.
  • Pestalotiopsis: A less common but equally damaging fungal disease that causes pimple-like lesions on the foliage.

Understanding these common arborvitae diseases is the first step in implementing effective tree care and preventive measures.

Identifying Arborvitae Diseases

Arborvitae disease starting from the bottom of tree and spreading upward, turning the foliage brown.

Early identification is crucial for effective treatment and sustaining your arborvitae’s health. Here’s how to recognize the symptoms:

  • Color Changes: Watch for foliage turning yellow or brown, which could indicate various issues, from fungal infections to root rot.
  • Twig Tips: Wilted or brown twig tips are often signs of twig blight.
  • Branch Dieback: Dead tissue at the ends of branches may indicate more severe conditions like arborvitae needle blight.
  • Physical Signs: Look for pimple-like lesions or fungal fruiting structures dotting the leaves, which could signify Pestalotiopsis or other fungal diseases.

By recognizing these symptoms early, you can take immediate action, whether chemical management or changing growing conditions, to prevent new infections and further damage.

Preventing Arborvitae Diseases

Prevention is often the best cure. Here are some strategies to keep your arborvitae healthy:

  • Proper Watering: Overwatering or underwatering can stress the tree, making it more susceptible to diseases. Make sure your arborvitae are getting enough water, but avoid waterlogged soils.
  • Good Drainage: Poor soil drainage can lead to root rot. Ensure your garden soil allows for adequate drainage.
  • Fertilization: Use fertilizer sparingly and according to recommendations, as excessive nutrients can also lead to disease problems.
  • Regular Pruning: Remove dead or diseased branches to prevent the spread of pathogens. Tree pruning is essential for good air circulation, which can deter fungal spores.

Following these preventive measures can create an environment where diseases are less likely to become established, thus safeguarding your arborvitae’s long-term health.

Treating Arborvitae Diseases

Gardener spraying fungicide on arborvitae to prevent diseases.

If your arborvitae already show signs of disease, immediate action is required. Here are some treatment options:

  • Fungicides: Fungicides can be effective for fungal diseases like twig blight and arborvitae needle blight. Always follow the instructions on the label.
  • Insecticides: Consider using insecticides for pest-related issues like spider mites and bagworms. Again, follow the manufacturer’s guidelines.
  • Soil Amendments: For soil pH affecting manganese availability, consider soil amendments like sulfur to lower soil pH.
  • Professional Help: For severe cases, consult certified arborists trained in the latest techniques for tree care and can provide more targeted treatments.

By applying the appropriate treatments, you can halt the progression of the disease and help your arborvitae recover.


Arborvitae is a versatile and generally resilient evergreen that can enhance any garden space. However, like all trees and shrubs, it’s susceptible to various diseases. Early identification, preventive measures, and appropriate treatments are vital in managing these issues effectively. By understanding the common diseases that affect arborvitae and how to treat them, you can ensure that your trees flourish and remain a beautiful addition to your garden for years.

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