Gail Ruhl, Interim P&PDL Director, Senior Diagnostician, Dept. of Botany and Plant Pathology, Purdue University
Have you noticed pink protrusions on the fruit of your hawthorn or dieback
of branches. Check your trees closely. You may find your tree to be infected
with Cedar-Quince Rust.
Cedar-quince rust affects quince (Chaenomeles), serviceberry (Amelanchier),
hawthorn (Crataegus), mountain ash (Sorbus) as well as many other plants in
the rose family and can cause a great amount of damage to the fruits, twigs
and thorns of susceptible plants. The rust fungus requires two different tree
species to complete its lifecycle. On the primary host, juniper or red cedar,
the fungus infects leaves and soft shoots, becomes perennial in the living
bark and causes swellings that girdle twigs and small branches. During damp
weather in April and May, orange spore masses emerge from infected, swollen
juniper twigs and may be splashed or blown to hawthorn, one of the alternate
hosts. On the hawthorn, this fungus causes distortion of fruit, twigs, and
buds. Fruits become shrunken and often die; twigs become enlarged and woody.
Pinkish-orange tubes, about the size of a pencil lead, protrude from affected
fruits and twigs and shed orange spores that are splashed or blown back to
the juniper, completing the life cycle of this rust fungus.
Effective control of this fungal disease includes both cultural and chemical
approaches.
Planting resistant varieties when installing new trees will reduce the need to
invest time and money into chemical control. The following Hawthorns have shown
some degree of resistance to rust.
* Crataegus crus-galli (Cockspur Thorn)
* C. intricara
* C. laevigata (Autumn Glory)
* C. phaenopyrum (Washington Thorn)
* C. pruinosa
* C. viridis (Winter King)
If rust is a chronic problem causing poor tree vigor, registered fungicides may
be used on the hawthorn. These fungicides are preventive and must be applied
several times during early spring to maintain a protective coating on developing
twigs and fruit. Fungicides such as chlorothalonil, mancozeb or triadimefon,
when used regularly during infection periods, will help control hawthorn rust.
When spring weather is dry fungicide applications are generally not required.
Read and follow label instructions regarding amounts of fungicide, method of
application, and safety precautions.
For more information, please see the following publications (pdf):
Cedar Apple and Related Rusts on Apples in the Home Landscape
Cedar
Apple and Related Rusts on Landscape Plants
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Image from: http://ohioline.osu.edu/hyg-fact/3000/3055.html |
Cedar-quince rust |
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