Cedar Rust Fungi Aecial Tubes Now Evident

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  For the last month the fungal tubes of the “aecial” stage of several cedar rust fungi, namely cedar-apple rust (Gymonsporangium juniper-virginianae) and cedar-hawthorn rust (G. globosum) have been evident on leaf undersides of hawthorns, as seen in the accompanying picture.

  These rust fungi spend about a year and half on certain junipers (in the Cupressaceae family) before microscopic spores of the fungus oozing from galls on the juniper blow in the spring to certain genera in the Rosaceae family such as hawthorns and apples and crabapples.

 

cedar rust symptoms on upper leaf surface

 

After causing lesions on the upper leaves of their rosaceous hosts, the fungus mates inside the leaves, emerging from the underside of the leaves and producing pustules that contain these fungal tubes we now see. These contain multitudes of microscopic spores that are now returning by wind to their alternate juniper hosts.     

 

cedar rust aecia on lower leaves