Cedar-Apple Rust: Orange Gel on Cedars, Spots on Apples

Those Orange "Warts" Are Cedar-Apple Rust

Two cedar trees develop hard knots that turn to orange slime in spring, then dry to brown. The owner worries about danger to the trees and nearby shrubs.

What It Is

Cedar-apple rust is a fungus requiring two hosts: cedar/juniper and apple/crabapple. On cedars, it forms golf-ball galls that "bloom" orange gelatinous horns in spring, releasing spores. It does not harm cedars; galls drop after a couple of years.

On Apple Hosts

The same spores cause yellow-orange leaf spots, fruit lesions, and premature defoliation on apples and crabapples. Fungicides are used on apples, but no treatment is needed on cedars.

Management

• If you have apples, plant resistant varieties or apply fungicides.
• On cedars, simply ignore the galls—they're cosmetic.
• Remove nearby wild apples if rust is severe.

Your cedars are fine; the "orange slime" is just the fungus reproducing.