Arborvitae Disease Management: Twig Blights and Tip Blight Control

Managing Diseases in Arborvitae (Thuja)

Arborvitae faces several twig and tip blights that can significantly impact ornamental quality. Understanding the differences between these diseases is essential for proper diagnosis and management.

Normal Seasonal Browning

Oldest branchlets turn brown in autumn and fall off. This is normal—branchlets (not scale leaves) are shed annually as part of normal development.

Kabatina Twig Blight

Kabatina thujae kills tips of one-year-old branches (brown/ash-gray), persisting for months. Larger branches can be invaded/girdled. Small black pimple-like fruiting structures form at dead/living wood junction; oval colorless spores microscopically.

Management: Prune/destroy infected twigs/branches. Both Kabatina and Phomopsis can occur on same plant. Apply fungicides.

Pestalotiopsis Tip Blight

Pestalotiopsis funerea causes tan/brown twig tips with black pimple-like fruiting structures dotting the surface.

Management: Protect from winter injury, drought, and other stresses. Apply fungicides.

Phomopsis Twig Blight

Phomopsis juniperovora kills branch tips (brown/ash-gray), persisting months. Larger branches invaded/girdled. Small black fruiting structures at dead/living junction; both oval and long thread-like colorless spores microscopically. See Kabatina above for comparison.

Management: Prune/destroy infected twigs/branches. Both can occur on same plant. Apply fungicides.

Differentiating Twig Blights

Key distinctions: Kabatina affects one-year-old tips with oval spores; Phomopsis has both oval and thread-like spores; Pestalotiopsis shows fruiting structures dotting the tip surface. All three benefit from stress reduction (winter injury, drought protection) and fungicide applications. Accurate diagnosis requires microscopic spore examination.

Integrated Arborvitae Health Program

Successful management: reduce stresses (winter injury, drought); regular pruning of infected material; tool sanitation; fungicide applications during high-risk periods; and accurate diagnosis to distinguish between the three blights and normal seasonal browning. The similarity in field symptoms makes laboratory confirmation valuable for targeted management.