There are orange jelly-like blobs growing on my cedar tree. What are they?

Those striking orange gelatinous masses are the telial horns of cedar-apple rust (Gymnosporangium juniperi-virginianae), a fascinating fungal disease that requires two different host trees to complete its life cycle — junipers/cedars and apple/crabapple trees.

How the disease cycle works:

• Brown, golf ball-sized galls form on cedar/juniper branches (these develop over 18 months)
• During warm spring rains, bright orange gelatinous tendrils (telial horns) emerge from the galls — this is what you're seeing
• These horns release spores that travel up to several miles on the wind to infect apple and crabapple leaves
• Infected apple leaves develop bright orange-yellow spots, and fruit may become deformed
• Spores from the apple leaves then travel back to infect cedars, completing the two-year cycle

What to do:

1. On cedar/juniper: Prune and destroy galls before the orange horns emerge (late winter is ideal). The galls do minimal harm to the cedar itself.
2. On apple/crabapple: Fungicide sprays containing myclobutanil can protect leaves if applied from pink bud stage through petal fall.
3. Long-term: If planting new trees, choose rust-resistant varieties of both crabapples and junipers.
4. Removing one host species within a few hundred feet can break the cycle, but wind-borne spores can travel miles, making this impractical in most landscapes.

The disease is rarely life-threatening to either host. See our Common Tree Diseases article for more regional disease information.