Cedar-apple Rust

(Gymnosporangium juniperi-virginianae)

Conservation Status
Cedar-apple Rust
 
  IUCN Red List

not listed

 
  NatureServe

not listed

 
  Minnesota

not listed

 
           
           
           
 
Description
 
 

Cedar-apple Rust infects apple trees and junipers. In the Rose family it infects prairie crabapple and paradise apple, rarely hawthorn. In the Cypress family in infects chiefly eastern redcedar but occasionally also creeping juniper and common juniper. These are the only species affected in Minnesota. Other apple (Malus) and juniper (Juniperus) species are affected in other areas.

On apple and crabapple trees, infections begin in the early spring. Bright yellow to orange spots (lesions), often with a red border, appear on the leaves in April and May. As the fungus matures, raised black spots form in the center of the spot on the upper leaf surface, and brownish threads or finger-like tubes, less than 1 10 long, form on the lower surface. Eventually, the tubes open to release yellow to orange spores. Rarely, the fungus infects fruit, forming large green to brown spots with black dots on the fruit surface.

On eastern redcedar, infections first appear in July and August. Abnormal, greenish-brown growths (galls) appear at the base of a needle or in a crack or crevice of a twig or small branch. As it matures it becomes pitted, more or less circular, and 1 or more in diameter. The following year, a short, pimple-like bump appears in each depression. The gall overwinters a second time in this form. In the second spring, eighteen months after infection, the bumps elongate, forming finger-like projections. During the first warm rain, sporulation occurs. The projections become bright orange, gelatinous, and ½ to ¾ long. This stage lasts for only about two days but may occur several times. The projections dry up, shrink, and become dark brown. The gall will remain on the tree for several years but will not produce more spores.

 
     
 

Similar Species

 
     
     
 
Habitat and Hosts
 
 

Anywhere eastern redcedar grows in close proximity to apples or crabapples, especially near apple orchards.

Evergreen hosts: chiefly eastern redcedar; occasionally also creeping juniper and common juniper.

Deciduous hosts: prairie crabapple and paradise apple; rarely hawthorn

 
     
 
Biology
 
 

Season

 
 

April and May

 
     
 
Distribution
 
 

Distribution Map

 

Sources

4, 7, 24, 26, 30.

 
  9/17/2021      
         
 

Occurrence

 
 

Common

 
         
 
Taxonomy
 
  Kingdom Fungi (fungi)  
  Subkingdom Dikarya  
  Division Basidiomycota (club fungi)  
  Subdivision Pucciniomycotina  
  Class Pucciniomycetes  
 

Order

Pucciniales (rust fungi)  
 

Suborder

Uredinineae  
 

Family

Gymnosporangiaceae  
 

Genus

Gymnosporangium  
       
 

Until very recently, the genus Gymnosporangium was placed in the family Pucciniaceae. Studies showed that the genus did not belong to Pucciniaceae orto any other existing rust family. In an article published 12/31/2020, it was proposed that a new family Gymnosporangiaceae be created to accommodate the genus. At that time the order Pucciniales (rust fungi) did not have any suborders. In an article published on 7/2/2021 a framework of seven suborders was proposed containing 80% of all rust species.

 
       
 

Synonyms

 
 

Gymnosporangium macropus

Gymnosporangium virginianum

Podisoma juniperi-virginianae

 
       
 

Common Names

 
 

Cedar-apple Rust

Juniper-apple Rust

 

 

 

 

 

 

 

 

Glossary

Gall

An abnormal growth on a plant produced in response to an insect larva, mite, bacteria, or fungus.

 

Sporulation

The process of forming spores.

 
 
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Randy

 
 

Cedar-apple rust gall on eastern red cedar, Freeborn County, MN, 2016

 
    Cedar-apple Rust      
           
 
MinnesotaSeasons.com Photos
 
    Cedar-apple Rust   Cedar-apple Rust  
           
    Cedar-apple Rust   Cedar-apple Rust  
           
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Other Videos
 
  CedarAppleRust
hoek0007 University of Minnesota
 
   
 
About

Published on Sep 7, 2015

University of Minnesota
Plant Pathology 1005
Disease of the Week
Cedar Apple Rust

   
  Cedar-Apple Rust (Juniper Rusts)
PurdueExtensionEntm
 
   
 
About

Published on Apr 30, 2015

The cedar rust diseases (Juniper spp.) stand out due to their conspicuous nature, and the fact the fungi that cause them complete their life cycles on two plant hosts — the juniper (cedar) and the apple (although pear, hawthorn, quince, serviceberry, and crabapple are other hosts). All potential host plants are commonly planted in the urban landscape, or are native to the Midwest. In Indiana, there are three common juniper rust diseases, Cedar-Apple Rust, Cedar-Hawthorn Rust, and Cedar-Quince Rust.

Regardless of the disease, these rust fungi have similar life cycles and cause similar symptoms in their hosts. In the spring, orange gelatinous horns develop from gray to brown colored fungal galls on the branches of infected junipers. These horns produce wind-blown spores that can infect apple and crabapple trees.

For more information, including management, please refer to our publication, “Cedar Apple and Related Rusts on Landscape Plants,” at: https://www.extension.purdue.edu/extm...

   
  Cedar Apple Rust
backyardfarmer
 
   
 
About

Published on Apr 17, 2016

Nebraska Extension Plant Pathologist Loren Giesler shows the orange gelatinous galls of cedar apple rust and talks about how to control them on both cedar and apple trees.

   
  Cedar-apple Rust
kdwpinfo
 
   
 
About

Published on May 1, 2009

Orange masses seen in cedar trees during rainy spells are caused by cedar apple rust. Learn about this complex tree disease here.

   
  Cedar Apple Rust - Common Plant Diseases in the Landscape and Garden
Virginia Cooperative Extension Master Gardener
 
   
 
About

Published on May 4, 2017

Join Virginia Tech Plant Pathologist, Mary Ann Hansen, as she discusses common plant diseases in Virginia. In this video she talks about Cedar-Apple Rust. Cedar-Apple Rust, like most other rust fungi, needs two hosts to complete it's life cycle. The first of which is spent on the Red Cedar where very distinctive (and creepy) galls form on the tree.

For more information on the Virginia Tech Plant Disease Clinic: https://www.ppws.vt.edu/extension/plant-disease-clinic.html

For more information on the Virginia Cooperative Extension Master Gardener Program: https://ext.vt.edu/lawn-garden/master-gardener.html

   

 

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  Randy
2016

Location: Freeborn County, MN

Cedar-apple rust gall on eastern red cedar

Cedar-apple Rust

 
           
 
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Created: 12/15/2017

Last Updated:

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