|
Contents (this page):
Cedar-Apple Rust
Others
Go to:
Rust Diseases
Intro to Rust Fungi
Plant Disease Profiles
Related Links
Glossary
PP318 Home
|
Gymnosporangium Rusts
Cedar-Apple Rust
 |
Cedar-Apple Rust is caused by Gymnosporangium
juniperi-virginianae, a heteroecious, demicyclic rust fungus. |
 |
 |
Infection of apple leaves by basidiospores
in the spring results in the development of bright yellow chlorotic spots. |
Spermagonia form on the upper leaf surface
shown here on the left. On the right is a cross
section through a spermagonium showing the
receptive hyphae and spermatia.
If fertilization occurs, aecia develop
on the bottom of the leaf directly beneath
the spermagonia. |
 |
 |
The aecia splits open at maturity releasing
aeciospores which are wind-disseminated to Juniperus species in
summer and early fall. |
 |
Severe infection of the alternate host apple
causes not only chlorotic leaf
spots but also defoliaton and degrade in
fruit and fruit production.
Infection of Juniperus needles results
in the formation of a gall the year following infection.
 |
The second year following infection of
junipers, telial horns are formed on the galls in early spring. |
If wet weather continues during telial formation,
telial horns can elongate up to 3 inches and
become gelatinous in consistency. If
dry weather occurs after telial horns have begun to
form, the horns can dry up (right) but will
resume growth upon the return of wet weather.
|
The two-celled teliospores of G. juniperi-virginianae
are formed and embedded in the telial horn. Each cell is capable of germinating
to produce a basidium and four basidiospores. |
 |
Other Gymnosporangium Rusts
Found in North Carolina
 |
Quince rust is caused by Gymnosporangium
clavipes. The telial stage occurs on juniper, causing a slight
swelling of the branches. Telia of this species are gelatinous and
pulvinate or hemispheric. |
 |
The aecia occur on the fruit and stems
of the alternate hosts, crabapple, quince
and hawthorn. |
 |
 |
Gymnosporangium nidus-avis causes
a witch's broom on juniper with the aecial stage on apple, hawthorn, quince,
and other rosaceous hosts. |
 |
 |
Gymnosporangium effusum can cause
swellings and cankers on juniper trunks as well as branches. The alternate
host is chokeberry. |
 |
Gymnosporangium ellisii causes severe
witch's broom on Atlantic white cedar which
may be a factor in forest stand reproduction
and use as a Christmas tree species. |
The alternate hosts for G. ellisii
are wax myrtle (Myrica cerifera) and sweet fern (Comptonia
peregrina). Here, spring-forming aecia
are beginning to appear on wax myrtle leaves.
Small, filiform telial horns are formed on
branches of the witch's broom on Atlantic
white cedar. Teliospores are formed and embedded
in these telial horns.
|
Gymnosporangium globosum causes
a small rounded gall on juniper with wedge-shaped gelatinous telial horns.
The aecial stage occurs chiefly on hawthorn, but also on apple, pear and
mountain ash. |
Return to the top of the page
Return
to PP318 course page
Dr. Larry Grand's Homepage
Email
Larry Grand
This website was prepared by Becky Bernard.
Last updated on 04 February 2008 by M.J. Munster
|
