Industry News: Tree Health

Orange growths on juniper trees signal cedar-apple rust

Thursday, June 14, 2018  
Posted by: Dana Walker
Many homeowners have been startled this spring by strange growths on juniper trees,
sprouting orange tentacles like miniature sea anemones.

The orange growths are nothing new, according to Sharon Yiesla, plant knowledge specialist at The Morton Arboretum in Lisle. They’re the most visible stage of a common fungal disease called cedar-apple rust, with a complex life cycle that involves both junipers and apple trees. “We’re seeing a lot of it this year because we’ve had so much rain,” she said.

The fungus that causes cedar-apple rust — so titled because some kinds of junipers are often erroneously called cedars — reproduces more readily in wet spring weather.

The disease usually does no lasting harm to the juniper tree or shrub, she said, but it can be a somewhat more serious matter for apple trees, including ornamental crabapple trees. Infected leaves get spots and may shrivel. Rust also can cause spots on apples, and may keep the fruit from developing or cause it to drop.

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