Botanic Garden >> Gardening > >> Question and Answer >> Plant Diseases

Orange Jelly-Like Growths on Thuja: Cedar-Quince Rust

Gooey Amber “Mandarin Orange” Clusters on Arborvitae

Small thuja trees bear clumps of gelatinous, amber, sectioned growths—cedar-quince rust (Gymnosporangium clavipes), a fungal disease requiring alternate hosts (rosaceous plants like quince, hawthorn).

Key Facts

Does not harm thuja significantly.

Galls dry and disappear on their own.

No fungicide needed on thuja; control focuses on alternate hosts if desired.

Search “cedar-quince rust” for images to confirm. Enjoy the alien-looking display—it’s temporary.

Plant Diseases

Balsam Fir Needlecast: Safe to Replant Balsams After Removal
Leaf Galls on Walnut and Oak: Harmless Insect Architecture
Mimosa Webworms and Wilt: Organic Control Options
Rust-Colored Gravel and Cedar Needles: Fertilizer or Irrigation Overspray?
Lichens on Trees: Harmless Indicators of Stress, Not Killers
Pine Disease in Neighborhood: Get Forester Visit
Thuja Green Giant Root System: Safe for Structures
Identifying and Treating Eucalyptus Rust in Spain
Petunia Pest Mystery: Black Spherical Specks on Buds and Leaves
Rust Disease on Chemical-Free Lawn: Let It Run Its Course

Garden Articles

Why Newly Planted Evergreens Turn Brown in Summer Heat
Saving Thuja (Arborvitae) from Drought and Spider Mites
Thuja (Arborvitae) Browning After Planting: Transplant Shock or Water Stress?
Tomato Seedling Spots: Need Photo and Seed Source
Aphids on Aspen: Honeydew, Sooty Mold, and Organic Management
Replacing Willows with Crepe Myrtles: Choose Aphid-Resistant Varieties
Apple Tree Yellowing and Fruit Drop: Multiple Possible Causes

Plants

White Jelly Blobs on Leyland Cypress: Fungal Issue?
Citrus Sooty Mold from Aphids: Indoor Winter Infestation Recovery
Black Dots on Blood Orange Leaves: Scale or Harmless Fungus?
Mulberry Sap Leak and Leaf Curl: Borer Damage
Sunflower Black Stem Deposits: Diagnosis Needed
White Pine Thinning & Tip Browning: Tip Moth, Weevil, or Roots?
Powdery Mildew on Potted Cherry Seedlings: Indoor Fungus Control