4 Common Rose Diseases
and how to prevent them...
1) Black Spot
Description: Fungal disease that occurs in damp conditions.
Symptoms: Circular dark brown or black spots with fringed
edges on leaves and stems. Leaves may turn yellow and drop off.
Prevention and Control: Choose resistant varieties; plant roses
in sunny locations with good air flow; and avoid wetting foliage
late in day. Remove fallen leaves and infected canes promptly.
Mulch to help prevent spread of spores. A solution made of 1
tablespoon of sodium bicarbonate (baking soda) and 1
tablespoon of vegetable oil per gallon of water may help. Use
sparingly, and don’t apply in bright sun. Avoid getting on soil and
flowers, because it can distort blossoms and affect soil pH.
2) Crown Gall
Description: Bacterial disease that affects root and/or stem
tissues of several woody plants, including roses.
Symptoms: Large, distorted growths appear near the plant's
crown or on roots. They eventually cause death.
Prevention and Control: Before you buy a plant, Inspect it for
early swelling. Avoid wounding plant, especially near soil line.
Provide good winter protection to prevent bark cracking. Once
plant is infected, disease is difficult to control. Remove infected
plants, and replace soil. If problem is severe, consider growing
non-susceptible plants in this spot for three to four years. Always
sterilize cutting tools with bleach-water if used on infected plants.
3) Powdery Mildew
Description: Fungal disease that spreads by airborne spores,
which survive winter on leaves and leaf buds.
Symptoms: White or gray powdery coating on leaves, shoots and
flower buds. Leaves may drop; buds may not open.
Prevention and Control: Plant disease-resistant roses in sunny
locations with good air flow; and remove diseased leaves and
flowers during and after growing season. Washing foliage
occasionally in mid-morning may disrupt daily spore-releasing
cycle. Always allow foliage to dry before evening. Baking soda
solution (see Black Spot) may also help.
4) Rust
Description: Fungal disease that's spread by wind and water
and thrives in cool, moist conditions. Survives winter on leaves
and stems.
Symptoms: Bright orange pustules on stalks, branches and leaf
undersides early in season. Later, pustules may turn yellow-
green on leaves, and eventually black.
Prevention and Control: Select resistant roses, and avoid
overhead watering late in day. Use drip irrigation or soaker
hoses. Mulching may prevent spores spreading. Destroy infested
plant material and prune back diseased stalks promptly. In fall,
remove fallen leaves and debris around plant.
and how to prevent them...
1) Black Spot
Description: Fungal disease that occurs in damp conditions.
Symptoms: Circular dark brown or black spots with fringed
edges on leaves and stems. Leaves may turn yellow and drop off.
Prevention and Control: Choose resistant varieties; plant roses
in sunny locations with good air flow; and avoid wetting foliage
late in day. Remove fallen leaves and infected canes promptly.
Mulch to help prevent spread of spores. A solution made of 1
tablespoon of sodium bicarbonate (baking soda) and 1
tablespoon of vegetable oil per gallon of water may help. Use
sparingly, and don’t apply in bright sun. Avoid getting on soil and
flowers, because it can distort blossoms and affect soil pH.
2) Crown Gall
Description: Bacterial disease that affects root and/or stem
tissues of several woody plants, including roses.
Symptoms: Large, distorted growths appear near the plant's
crown or on roots. They eventually cause death.
Prevention and Control: Before you buy a plant, Inspect it for
early swelling. Avoid wounding plant, especially near soil line.
Provide good winter protection to prevent bark cracking. Once
plant is infected, disease is difficult to control. Remove infected
plants, and replace soil. If problem is severe, consider growing
non-susceptible plants in this spot for three to four years. Always
sterilize cutting tools with bleach-water if used on infected plants.
3) Powdery Mildew
Description: Fungal disease that spreads by airborne spores,
which survive winter on leaves and leaf buds.
Symptoms: White or gray powdery coating on leaves, shoots and
flower buds. Leaves may drop; buds may not open.
Prevention and Control: Plant disease-resistant roses in sunny
locations with good air flow; and remove diseased leaves and
flowers during and after growing season. Washing foliage
occasionally in mid-morning may disrupt daily spore-releasing
cycle. Always allow foliage to dry before evening. Baking soda
solution (see Black Spot) may also help.
4) Rust
Description: Fungal disease that's spread by wind and water
and thrives in cool, moist conditions. Survives winter on leaves
and stems.
Symptoms: Bright orange pustules on stalks, branches and leaf
undersides early in season. Later, pustules may turn yellow-
green on leaves, and eventually black.
Prevention and Control: Select resistant roses, and avoid
overhead watering late in day. Use drip irrigation or soaker
hoses. Mulching may prevent spores spreading. Destroy infested
plant material and prune back diseased stalks promptly. In fall,
remove fallen leaves and debris around plant.
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Phone: 208-336-1285 MST
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| Published in Gardening How-To Magazine March/April 2006 |
More on this subject:
4 Common Pests
Rose Resources
Return to Main Article
4 Common Pests
Rose Resources
Return to Main Article
