Cedar-apple rust and other similar rusts

Quick facts

  • Do not plant trees, shrubs or other plants in the rose family (Rosaceae) within a few hundred yards of juniper and cedar.
  • Plant disease resistant varieties when possible. 
  • All four Gymnosporangium fungi in Minnesota require two different hosts to complete their life cycle; one plant from the cypress family and the other from the rose family.
  • The rust fungi rarely cause serious damage to their hosts and usually do not require management.
  • A few highly susceptible plants may suffer shoot death or defoliation from leaf spots.

The rust fungi, known as Gymnosporangium, cause unique and fascinating diseases that require two different living plant hosts in order to complete their life cycle.

Although the bright red and orange leaf spots and orange gelatinous galls symptomatic of these diseases are quick to draw attention, the disease rarely causes serious damage to its hosts and often does not require management in a home landscape. A few highly susceptible plants may suffer shoot death or defoliation from leaf spots.

Do not plant alternate hosts of the rust fungi from the rose family (Rosaceae: apple, crabapple, chokecherry, cotoneaster, etc.) near juniper and cedar hosts. 

Identifying rust

These diseases require two different plants in order to complete their life cycle. Symptoms are very different on each type of plant.

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Managing rust

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Rebecca Koetter and Michelle Grabowski, Extension educator

Reviewed in 2018

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