by Nanette Londeree, Master Rosarian
SYMPTOMS
- White, gray or silver talcum-powder-like growth on the tops of leaves, primarily new growth
- May appear on stems, buds or sepals
- First observed on new growth and distorts or curls the edges of leaves; leaves may be permanently twisted
- Growing tips and buds may look badly deformed or be killed
- When the disease is severe, plants become stunted and leaves curl and drop
- Mature leaves are generally not infected
CAUSE
- Infection by the fungus Sphaerotheca pannos var rosae
- Airborne spores infect tender new growth
OPTIMAL CONDITIONS
- Most prevalent in spring and fall
- Temperatures 60 – 80°F, with 40 – 70% relative humidity during the day, and up to 95% at night
- Does not need free water to reproduce
- Fungus can overwinter as dormant mycelium or resting spores on infected stems and leaves
TREATMENT
Prevention:
- Buy and plant disease-free plants
- Choose resistant varieties; glossy foliaged varieties generally have better resistance to most fungal diseases
- Plant roses in areas with good soil drainage and ventilation; avoid shady spots and dense plantings
- Maintain good garden sanitation; remove and destroy infected leaves and canes during the season
- Water leaves daily (overhead) in the morning
- Spray with baking soda and horticultural oil, anti-transpirants, botanicals such as Neem oil
- Dormant spray with horticultural oil and copper or lime sulfate after pruning
Elimination:
Spray with baking soda and horticultural oil; for additional information on management, visit the UC IPM website
GOOD GUY / BAD GUY?
Definitely a Bad Guy. One of the most common diseases of roses and other plants