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Rose Diseases (Outdoors)

Informational table showing disease name, symptoms, pathogen/cause, and management of Rose Diseases (Outdoors) diseases.
Disease Symptoms Pathogen/Cause Management
Anthracnose Dark-purple to black spots are bordered by a narrow, dull-brown band. Centers of spots turn gray and fall out. Spots similar to leaf spots form on canes. Sphaceloma rosarum Maintain good sanitation. Black spot control procedures (below) also control anthracnose.
Black spot Brown to black round spots with feathery edges form on leaves. Leaves yellow and fall. Small, purplish spots form on canes. Diplocarpon rosae Remove infected canes. Remove and destroy fallen leaves. Water in a manner that keeps foliage surfaces dry. Apply a fungicide to protect new foliage.
Botrytis blight Small, water-soaked lesions form on petals. Gray fungal growth covers infected petals. Stubs left after harvest become infected. The fungus then moves down to girdle the cane. Botrytis cinerea Space plants to ensure good air circulation. Remove fading flowers and yellowing leaves. Apply a fungicide protect healthy tissue.
Cankers Reddish-brown spots on canes turn light to dark brown and become covered with tiny, black dots (fungal fruiting structures). Cankers girdle and kill the cane. Coniothyrium, fuckelii, Cryptosporella umbrina, Coniothyrium wernsdorffiae, Cylindrocladium scoparium Do not plant stock with cankers. Remove infected canes, making the cut immediately above a bud. Apply a fungicide after pruning. Sterilize the shears with a disinfestant between cuts. Maintain even soil moisture and moderate fertilization.
Crown gall Small white to cream-colored galls that form on stems may enlarge to 6 inches in diameter. Galls can form on roots or stems. Agrobacterium tumefaciens Do not plant infected material. Apply Agrobacterium radiobacter to protect healthy plants at transplant.
Downy mildew Purplish-brown spots form on leaves during cool, damp spring weather. Leaves yellow and fall. Small spots or long, purplish areas may form on and kill twigs. Peronospora sparsa Water in a manner that keeps leaf surfaces dry. Apply a fungicide.
Powdery mildew Spots on leaves, stems, and flower parts expand and become covered with white fungal growth. Small dead spots form on some cultivars. Sphaerotheca pannosa Apply a fungicide .
Rose Rosette Leaves are distorted and often bright red. Canes are excessively thorny and mature very slowly. Plants may branch excessively (witches’-broom). Rose rosette virus vectored by eriophyid mites. Destroy infected plants. Eliminate multiflora roses in a 100’ radius of desired roses.
Rust Lower leaves and cane tissue in the spring and summer have masses of orange powdery spores. Black spores form on the leaves and other parts in autumn. Phragmidium Infected plants should be immediately destroyed since this disease is not common in the U.S. and poses a serious threat to roses. Bury infected plant material or seal in a plastic bag and send it to a landfill. Only roses are susceptible. The fungus will die quickly if no roses are available for infection.
Viruses Leaves may exhibit mosaic, mottling, yellow line, or ring patterns. Veins may turn yellow. Rose mosaic, mottle, yellow mosaic, ring pattern, or streak virus. Tobacco streak. Rose rosette, rose wilt, spring dwarf, or color break virus. Strawberry latent ring spot. Destroy infected plants. Plant only healthy, virus-free plants. Maintain good insect and mite control.

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Rose black spot on leaves and cane.

Anthracnose
Anthracnose.

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Downy mildew.

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Powdery mildew on leave and flower stem
Powdery mildew on leave and flower stem.

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Virus symptoms
Virus symptoms.

Canker symptoms and fruiting structures
Canker symptoms and fruiting structures.

Rust
Rust.

Crown gall
Crown gall.

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Article Details

Title

Rose Diseases (Outdoors)

Code

XL0068

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