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Plantwise Technical Factsheet

rose rust (Phragmidium mucronatum)

Host plants / species affected
Rosa (roses)
Rosa alba
Rosa canina (Dog rose)
Rosa centifolia (Cabbage rose)
Rosa damascena (Damask rose)
Rosa gallica (French rose)
Rosa majalis (cinnamon rose)
Rosa rubiginosa (sweet briar)
Rosa rugosa (rugosa rose)
Rosa villosa (apple rose)
List of symptoms/signs
Fruit  -  discoloration
Fruit  -  lesions: scab or pitting
Leaves  -  abnormal colours
Leaves  -  abnormal leaf fall
Leaves  -  fungal growth
Leaves  -  yellowed or dead
Stems  -  discoloration
Stems  -  distortion
Stems  -  galls
Stems  -  mould growth on lesion
Whole plant  -  discoloration
Symptoms
In spring, minute, glistening, reddish-orange spermogonia appear on the adaxial leaf surface and/or petioles, branches and young canes. Aggregated aecia with bright orange-yellow, powdery masses of aeciospores are subsequently formed on the abaxial leaf surface opposite the spermogonia or surrounding the spermogonia on the petioles and canes. Heavy aecial infection may cause distortion or malformation of the infected leaves, petioles, branches and canes, and abundant aecial production may produce a reddish-orange, gall-like appearance.

From early summer to autumn, minute, uredinia with bright orange-yellow masses of urediniospores are produced on the abaxial leaf surface, branches and canes. The sori may be scattered or densely aggregated, but do not cause any appreciable distortion, unlike the aecial infection. Heavy uredinial infection causes early yellowing of the infected leaves and premature defoliation. The uredinia are quickly replaced by blackish masses of teliospores and the abaxial surface of infected leaves may appear blackish and dusty. When the braches and canes are infected, the urediniospore and teliospore production follows the aeciospore production, and the infection may become perennial and cause canker on the infected shoots.
Prevention and control
Cultural Control

Rose cultivars vary greatly in their resistance/susceptibility to P. mucronatum; thus, the selection of resistant cultivars is recommended. As rust infection may be perennial on canes, plants should be examined thoroughly when purchasing stocks to ensure that no cane infection is present on the plants.

As roses are not cultivated on an industrial scale, with the exception of oil roses (Rosa damascena), sanitary practices are preferred and are reasonably effective. Fallen leaves bearing teliospores should be collected and burned in the autumn. Shoots with teliospore-producing cankers must be completely pruned out. The removal of neglected and almost wild roses is also highly recommended. Careful pruning-out of shoots and leaves with spermogonial/aecial infection in the early spring will greatly reduce the spread of the disease.

Proper spacing and pruning of rose bushes provides adequate solar exposure and ventilation, which reduces rust infection. In the greenhouse, adequate ventilation and the prevention of water condensation are recommended. Overhead irrigation should be avoided in the late afternoon or evening.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Biological Control

No effective biological control organisms against P. mucronatum have been developed or tested.
Related treatment support
Plantwise Factsheets for Farmers
Benh Vien Cay An Qua Dong Bang Song Cuu Long; Thuoc Vien Nghien Cuu Cay An Qua Mien Nam; CABI, Vietnamese language
 
 
External factsheets
University of California IPM Pest Management Guidelines, University of California, 2009, English language
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