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Botrytis (gray mold) on Roses

Botrytis cinerea
Updated Oct 10, 2024
 
1

Make a Positive Identification

  • Sunken, smooth, grayish spots may appear on the buds and flower stem.
  • Infected buds may fail to open.
  • Flowers may develop spots.
  • Young, green canes may develop large, sunken, dead areas.
  • A fuzzy, gray-brown growth develops on decaying tissues.
  • It can infect cut or damaged stems.

Gray mold also infects other plants, including: african violet, blueberry, daphne, fig, fuchsia, geranium (pelargonium), grape, hydrangea, impatiens, peony, primrose, petunia, rhododendron, rosemary, raspberry, snapdragon, strawberry and many others.

Species: Gray mold
Rose flower petals with darker spots

Melody Putnam, Oregon State University

On rose petals, gray mold may appear as small, light-colored spots surrounded by reddish halos.

Species: Gray Mold
Unopened bud turning brown

Dr. Parthasarathy Seethapathy, Amrita School of Agricultural Sciences, Bugwood.org

Sunken, grayish spots may appear on the flower buds and stems. Buds may fail to open and often droop.

Species: Gray mold
Stem with brown, sunken area and gray mold growing

Jay Pscheidt, Oregon State University

Young, green canes may develop large, sunken, dead areas.

Species: Gray Mold
Dead rose growing fuzzy gray mold

"Botrytis cinerea" by Flowersabc is licensed under CC BY-SA 2.0

A fuzzy, gray-brown growth develops on decaying tissues.

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2

Botrytis (gray mold) on Roses Benefits

Rose gray mold is a plant disease that harms susceptible rose plants. It doesn’t have any benefit for people or the environment.

 

Botrytis (gray mold) on Roses Risks

  • Gray mold causes damage to flowers, leaves, and stems.
  • Canes may be girdled, causing stems to collapse.
  • It can be a serious problem in the high humidity of a greenhouse.
Risk Card
Does it cause harm?
Adults & Children
None
Property
Low
Pets
None
Annoyance
Some
Environment
None
Action Optional
 
3

TAKE ACTION?

Gray mold ruins flowers and damages plants. If you don't like how it looks, you will need to take action.

Do I need to take action?
If you don’t like how it looks, you will need to take action.

What if I do nothing?
Rose gray mold disfigures flowers and damages plants.

 
4

PREVENT GRAY MOLD ON ROSES

Roses in containers at store

rcmirani, iStock

Don’t bring diseased roses into your garden
  • Inspect new rose shrubs for signs of disease before buying.
Loppers cutting a rose cane

Signe Danler, Oregon State University

Prune roses to promote airflow
  • Thin out and space canes to open up the center of the shrub. This helps the leaves dry quickly after rain to reduce disease pressure.
  • Avoid overhead watering.
  • When planting rose bushes leave enough space between plants to ensure good airflow.
  • Plant roses in full sun.
 
5
HOW TO GET RID OF ROSE GRAY MOLD

Gray mold spreads most easily in cool, damp weather.

Prevention

  • Don’t bring diseased roses into your garden.
  • When planting rose bushes leave enough space between plants to ensure good airflow. Plant in full sun.

Non-chemical Methods

  • Remove and destroy stems, leaves, & flowers showing disease.
  • Rake up diseased leaves.
  • Prune established rose plantings to promote air flow. Good air flow reduces the conditions that favor plant diseases.
  • Avoid overhead sprinklers. If overhead sprinklers must be used, try to irrigate early in the day to allow leaves to dry.

Chemical Methods

  • Fungicides are available for gray mold. Fungicides are pesticides that target fungal diseases.
  • They must be applied before plants develop disease symptoms to work. Follow the label directions for best results.
  • Control of gray mold with fungicides is difficult. Non-chemical control is more likely to be effective.

NEED HELP?

Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon  and other states  can suggest other methods.

Jump to

Method Does it work? Is it safe? Recommendation
A
Sanitation
Effective
Low risk
Recommended
B
Control with Fungicides
Somewhat effective
Moderate risk
Use if Necessary
C
If Using Fungicides, Protect Yourself & Minimize Risks
 
A

Sanitation

Non-Chemical Method

"cobwebs" by anjollie123456 is licensed under CC BY-NC-ND 2.0

Sanitation

Recommended

Remove stems, leaves, & flowers showing disease.This reduces spread of the disease.
Clean up and destroy all dead plant materials. Rake up diseased leaves.

Does it work?
Effective

These non-chemical strategies help minimize rose disease problems.
How much effort?
Moderate effort
What's the risk?
Low risk
Possible risk of exposure or harm from chemicals
NONE
Yard debris bin

Weston Miller, Oregon State University

Dispose of diseased material in your debris bin, compost pile, or burn pile.  Don’t use homemade compost that includes diseased rose material to amend the soil near your rose bushes.

 
B

Control with Fungicides

Chemical Method: Use with caution

iStock

Control with Fungicides

Use if Necessary
Does it work?
Somewhat effective

Control of rose gray mold with fungicides is difficult.
How much effort?
Moderate effort
What's the risk?
Moderate risk
Possible risk of exposure or harm from chemicals
El uso de fungicidas conlleva cierto grado de riesgo. El riesgo más bajo se produce sin el uso de fungicidas.

You may be exposed to a fungicide if you:

  • Get it on your skin
  • Breathe it in
  • Eat or smoke afterward without washing hands
  • Touch or eat plants that are wet with spray (you, pets, or children)
  • Bring it inside on your shoes or clothes

Follow directions closely to reduce risk.

Some products are available for home use. A few are listed below. These active ingredients are suggested chemical treatments to control rose gray mold (botrytis). Look for these chemical names in the “Active Ingredients” section of product labels.

  • Bacillus amyloliquifaciens strain D747
  • Chlorothalonil 
  • Copper fungicide 
  • Captan

Suggested pesticides are from the Pesticide Information Center Online (PICOL) Database. They are permitted for HOME use in Oregon. Read the label for application directions and effectiveness information.

ONLY professional pesticide applicators can use Restricted-Use Pesticides (RUP) that may be more effective. If you need further support, contact a licensed pesticide applicator.

Example label with active ingredient Bacillus amyloliquifaciens strain D747

Sample product label with Active Ingredient(s) highlighted

A red box on the example label highlights active ingredient Bacillus amyloliquifaciens strain D747. Uses a naturally occurring bacterium to suppress fungal infections.

Fungicide Application Tips

  • Proper timing of fungicide sprays is important for them to be effective against rose gray mold. Read the label carefully for application and frequency.
  • Fungicide products work best when applied before the disease appears. It is very difficult to control rose gray mold with fungicides once symptoms appear.
  • Researchers recommend alternating products (by active ingredient). Local populations of rose gray mold may develop resistance if only one type of fungicide is used repeatedly.
  • Using fungicides comes with real risks. ALWAYS read the entire label front to back. Review instructions even for brands you know.
 

If Using Fungicides, Protect Yourself & Minimize Risks

Chemical Method: Use with Caution
Gloved hands holding fungicide package to read label

Weston Miller, Oregon State University

Why Is It Important to Read Fungicide Product Labels?

  • They have detailed information on how to use the product correctly and legally.
  • They contain information on potential hazards of the product.
  • They provide instructions you should follow for poisonings and spills.
  • Following label instructions helps you to minimize the risks and maximize the benefits.

Key Fungicide Safety Tips

  • Read the entire label front to back.
  • Follow the instructions.
  • Review the instructions even for brands you know.
  • Only apply the product where the label says it can be applied.
  • Keep all fungicides in their original container.

The Label is the Law

ALWAYS read the label before using fungicide products. The label is a legal document that provides information on how to safely use the fungicide. This helps avoid harm to human health and the environment. Using a fungicide in off-label ways is illegal. It can result in legal enforcement actions.

READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.

  • Labels are different for every product and they often change over time.
  • Use a magnifying glass for small print.
  • Pay attention to CAUTION, WARNING, and DANGER statements.
  • Pay attention to the PRECAUTIONARY STATEMENTS.
  • The law states you must read and follow fungicide instructions.

Protect Yourself
Eye, skin & lung irritants

  • Wear the correct personal protection equipment. The right gear often includes chemical-resistant gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
  • Mix fungicide products outdoors or in a well-ventilated area.
  • Wash hands after you mix or apply fungicides and before smoking or eating.
  • Wash clothes worn while mixing and applying fungicides separately from all other laundry.

Protect Children & Pets
Children and pets are at risk if they eat or touch the plant before fungicides dry.

  • Keep them away during and after applying fungicides (read label for how long).
  • Remove toys and pet dishes from yard before applying.
  • Don’t track fungicide products into home on shoes or clothes.

Protect Pollinators

  • Apply early morning or evening when bees are less active.
  • Avoid spraying flowering plants, if possible.
  • Don’t spray on bees or insects.

Storage & Disposal

  • Store out of the reach of children and pets.
  • Store in a cool and dry place.
  • Never pour down any drain.
  • If you mix too much, apply it rather than storing it.
  • Don’t put fungicide containers in the trash unless instructed by the label.
  • Take unused fungicides to a hazardous waste facility.

Call  1-800-CLEANUP (1-800-253-2687) to find out where to dispose of pesticides.

For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call  503-234-3000, email   or visit Metro’s website  

More about:

About Using Pesticides on School Grounds in Oregon

If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management  (Oregon Department of Agriculture).

NEED HELP?

The National Pesticide Information Center (NPIC)  can answer questions about pest control chemicals.
 1-800-858-7378 or npic@ace.orst.edu  

Consider using a licensed pest or weed control company. Learn How to Hire a Pest Control Company.

Your local Extension Specialist in Oregon  and other states  can suggest other methods.

SEE OTHER COMMON PACIFIC NORTHWEST INSECTS, SLUGS & DISEASES ON PLANTS

Content provided by Signe Danler. Pesticide safety information edited by Kaci Buhl.

  Peer review facilitated by OSU Department of Horticulture.

Signe Danler

Signe Danler (Editor/Writer)

Signe Danler is a veteran Master Gardener and landscape designer, with an MAg degree in Horticulture from OSU, and an emphasis on Urban Horticulture. As instructor for the OSU Extension Service online Home Horticulture and Master Gardener Program, she uses her experience and training in gardening, urban forestry and ecological landscaping to communicate about and promote sustainable gardening and landscaping practices.

Photo of Kaci Buhl

Kaci Buhl

At the state level, I lead the Pesticide Safety Education Program (PSEP). The program hosts live recertification events around the state, serving over 1,000 licensed pesticide applicators each year. We also produce web-based training modules and license-preparation study manuals. Special training for unlicensed pesticide applicators is also available through a grant from the USDA Specialty Crop Block Grant Program. The PSEP at OSU works closely with the Oregon Department of Agriculture's Pesticides Division.

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