-
Pest SolutionsPESTS + WEEDSUSING PESTICIDES OR HERBICIDES?
I should be a large image.
Sudden Oak Death (SOD) and Ramorum Leaf Blight
Phytophthora ramorum
Updated Mar 06, 2025
Make a Positive Identification
Sudden Oak Death (SOD) and ramorum leaf blight are two different diseases. They are both caused by the fungus-like, non-native microorganism Phytophthora ramorum. It cannot be identified by symptoms alone. Many other diseases, insects, and physical stresses cause similar symptoms. A sample must be analyzed in a laboratory.
- Phytophthora ramorum is known to infect more than 100 species of trees, shrubs, herbs, and ferns, including some oaks.
- In Oregon forests, tanoak (Notholithocarpus densiflorus) is the primary host for Phytophthora ramorum. Once tanoak is infected, the disease typically kills them within one to three years. Some true oak species are susceptible to P. ramorum: Canyon live oak (Quercus chrysolepis) and California black oak (Q. kelloggii). They can die when infected. However, in Oregon these species mostly grow outside the range of P. ramorum. They have not been found to be infected by the pathogen in Oregon.
- Oregon white oak (Quercus garryana) is not infected. Only oaks in the red or intermediate groups have been found susceptible.
- Native plants growing among infected tanoaks can often be infected. They include: Douglas-fir, bigleaf maple, cascara, myrtlewood, Pacific madrone, native rhododendrons, huckleberry, kinnikinnick, and salmonberry.
- P. ramorum has also been found in nursery plants. These include common landscape plants, like rhododendron, camellia, pieris, viburnum, and kalmia.
Phytophthora ramorum causes two types of symptoms depending on the host plant.
- Trunk hosts, like tanoaks and oaks, get infections in their bark: Cankers girdle the tree and are often fatal. This is called Sudden Oak Death (SOD). SOD occurs only on the coast, within the range of tanoak.
- Foliar hosts, like rhododendron or camellia, get leaf spots, shoot blight or twig dieback. The disease often starts at the leaf tip where water collects. This symptom is called “drip tip”. This is called ramorum leaf blight or shoot dieback rather than SOD. It is seldom fatal. Infected plants have been found all over Oregon, usually in infested nursery plants.
Symptoms of Sudden Oak Death
Species: Sudden Oak Death
Joseph OBrien, USDA Forest Service, Bugwood.org
A canker under the bark oozes a dark black to red or amber sap, a symptom called ‘bleeding’. The trunk will show a discolored area. At first oozing sap appears on intact bark without wounds. Later the bark may split.
Tanoak trees may be infected without showing cankers or oozing sap.
Species: Sudden Oak Death
Underneath the bleed you will find red to dark brown discoloration. This is where tissues have died under the bark. They may be sunken, with a dark red margin. They usually occur within 3-15 feet of the soil line. Larger tanoaks show symptoms while younger ones do not.
Species: Sudden Oak Death
Ebba Peterson, Oregon State University IPM Center
Tanoak is highly susceptible to P. ramorum. Branches, twigs, leaves, and leaf stems may become infected. Petioles often turn black. New leaves on tanoak suddenly turn brown and droop. This can happen to the entire crown, or gradually to single leaves.
Species: Sudden Oak Death
"Tan Bark Oak" by bgwashburn is licensed under CC BY 2.0
The leaves on an infected tanoak tree rapidly turn brown. Dead leaves may stay on the tree for up to a year. Sprouts may grow from the base of the tree. The sprouts are likely to become infected quickly.
Diseased oak trees tend to be attacked by other organisms like bark beetles, ambrosia beetles, and decaying fungi. These further weaken the tree.
Symptoms of Ramorum Leaf Blight
Species: Douglas-fir and grand fir
"File:Sudden oak death on a Douglas fir (37034662014).jpg" by Oregon State University is licensed under CC BY-SA 2.0
On Douglas-fir and grand fir, a P. ramorum infection is called Ramorum Shoot Dieback. Symptoms appear only on new shoots and needles. They can resemble frost damage.
A few infected Douglas-fir and grand fir shoots have been found in Curry County. They were growing directly beneath infected tanoaks.
Species: Rhododendron
Leaf blight: Joseph OBrien, USDA Forest Service, Bugwood.org
Shoot tip dieback: Everett Hansen, OSU
On Rhododendron, a P. ramorum infection is called Ramorum Leaf Blight and Shoot Dieback. Symptoms look similar to infections caused by other pathogens.
Leaves may have dead tips or spots. Stems and central veins may turn black, followed by the death of attached leaves.
Most species and hybrids of Rhododendron are susceptible. Rarely, P. ramorum can kill entire branches.
Species: Viburnum
Jennifer Parke, Oregon State University
On Viburnums, a P. ramorum infection appears as Leaf Blight and Shoot Dieback. Infected leaves may die and fall off, leaving dark, leafless stems.
Species: Pieris
Nancy Osterbauer, Oregon State University
On Pieris, leaves infected with P. ramorum turn brown. Young shoots and leaves are most likely to get infected. Older plants may lose infected lower leaves.
Species: Camellia
Cheryl Blomquist, Oregon State University
On Camellias, leaves infected with P. ramorum develop dark areas. Young leaves may turn completely brown and brittle. The infection may travel down into the stem. Infected leaves may fall off within a few days, even without visible symptoms. This can leave bare branches, which sometimes die. Flower buds may also be infected in wet weather.
Susceptibility varies among Camellia species, hybrids, and cultivars.
Lookalikes: Diseases and physical damage
Species: Phytophthora leaf blight
N. Grunwald, Oregon State University
Phytophthora leaf blight (Phytophthora spp.)
Other Phytophthora species can cause leaf symptoms identical to P. ramorum, including leaf spot and twig dieback. Only lab testing can correctly diagnose which is present.
Species: Phytophthora root diseases
Jay Pscheidt, OSU
Phytophthora root diseases (Phytophthora spp)
Phytophthora root and collar rot is caused by many species of Phytophthora. The symptoms vary between plant species. They include yellowing, wilting, and death of the plant.
Only lab testing can correctly diagnose which is present.
Species: Armillaria root disease
William Jacobi, Colorado State University, Bugwood.org
Armillaria root disease (Armillaria mellea)
Armillaria is a fungus. As with SOD, leaves and twigs turn yellow, wilt, and die. Roots may decay. Some trees, like pines, may develop trunk cankers. Trees may die completely.
Armillaria can be identified by sheets of mycelium under the bark. There may also be honey mushrooms at the base of the trunk.
Species: Bacterial wetwood
Jay Pscheidt, OSU
Bacterial wetwood (Enterobacter, Bacillus, and Pseudomonas spp.)
Wetwood is a bacterial infection that occurs when a tree is injured. It causes bleeding on trunks and large branches of oak trees, like SOD. Unlike SOD, the bleeding is abundant, watery, and foul smelling. Bleeding from SOD is sticky and red when rubbed between your fingertips.
Wetwood has been found in elm, willow, and locust, especially in eastern and southern Oregon. Only lab testing can correctly diagnose it.
Species: Bleeding stem cankers
Jay Pscheidt, OSU
Bleeding stem cankers, Phytophthora canker (Phytophthora spp.)
Many Phytophthora species, including some native species, can cause canker symptoms identical to P. ramorum (SOD). These infect many common native and ornamental species.
Only lab testing can correctly diagnose which one.
If SOD infected other plants in besides tanoak, it would be more widespread. It is more aggressive than many other Phytophthora species.
Species: Artist conk
Joseph OBrien, USDA Forest Service, Bugwood.org
Artist conk (Ganoderma applanatum)
Oaks can be infected by many heart rot pathogens. Early signs of infection can include bleeding that looks identical to SOD, and branch dieback. Signs of infection often include conks growing at the base of the tree or out of the trunk. P. ramorum will kill a tree faster than a decay pathogen. It never produces conks, and does not cause decay.
Species: Physical damage
Dave Powell, USDA Forest Service (retired), Bugwood.org
Physical damage
Many events and injuries can cause symptoms that resemble Ramorum Leaf Blight. These include fertilizer burn, chemical injury, insects, drought, freezing, sunburn, and root damage. For instance, browning of leaves or branches from drought, sun or frost can look like dieback. If the plants recover and new foliage does not show symptoms, it is less likely this is Phytophthora.
Sudden Oak Death (SOD) and Ramorum Leaf Blight Benefits
- Sudden Oak Death (Phytophthora ramorum) is a plant disease that harms or kills susceptible plants. It doesn’t have any benefit for people or the environment.
Sudden Oak Death (SOD) and Ramorum Leaf Blight Risks
RISKS
- SOD threatens major industries in Oregon. These include timber, floral-greens, Christmas trees, and plant nurseries. Work to contain it has cost over $35 million from 2001 to 2022.
- SOD threatens plant and wildlife communities and food resources. It can alter the function of ecosystems.
- The dead trees left by SOD promote more frequent and intense wildfires. Slope stability may be reduced, increasing landslides.
Risk Card
Does it cause harm?
Adults & Children
None
Property
Some
Pets
None
Annoyance
Some
Environment
High
Action Recommended
Take Action
Sudden oak death is a serious invasive plant disease. It is very important to prevent it from spreading to new areas.
Do I need to take action?
If you see a plant with suspicious symptoms, consider these questions:
- Is the plant susceptible to SOD? APHIS list of host plants
- Do the symptoms match those for SOD?
- Is it growing in an area where other plants are infected with SOD? See a Map of Oregon Quarantine Area at the Oregon Sudden Oak Death site.
If you suspect you have found a P. ramorum-infected plant in Oregon, report it to the Oregon Dept. of Agriculture.
What if I do nothing?
- The only way to keep P. ramorum from spreading is to identify and stop new infestations.
- SOD will cause more harm if it spreads. It will cost even more to Oregon’s natural areas, and nursery and forestry industries.
Prevent SOD from Spreading
Oregon Dept of Agriculture sign
Don’t Transport Infected Materials
People are the primary way the infection spreads to new areas. They move potted plants or infected wood, leaves, and stems. This can transfer P. ramorum to uninfected areas.
If you live in or visit a quarantined area in southwest Oregon or California:
- Don’t transport firewood, plant materials, or soil from quarantined areas.
- Stay on established trails. Don’t go on trails that are closed.
Shawna Horner, Oregon State University
Before Leaving an Infested Area:
- Clean soil off shoes, tools, tires, horses’ hooves, and pets’ paws. Use a wire brush to remove soil from shoes and tools.
- Disinfect any tools you have used in an infested area. Use a 10% bleach solution or disinfectant (like Lysol).
- If you drive through an area with SOD, clean mud, dirt and leaves off your vehicle.
"Rhododendron macrophyllum" by Oregon Department of Agriculture is licensed under CC BY-NC-ND 2.0
Purchase Healthy, Disease-free Plants
- Inspect all plants for signs of disease. Don’t purchase plants with disease symptoms.
- Be wary of free plants that may be diseased.
- Be especially careful with species that are very susceptible to P. ramorum.
- Quarantine new plants for 4-6 weeks before placing them near other susceptible plants.
The native Rhododendron in the picture shows signs of disease. Don't buy it.
"Rhododendron 'PJM' ( Peter J. Mezitt, late1930s) 2020 photo" by F. D. Richards is licensed under CC BY-SA 2.0
Plant Resistant Species
If possible, use plants that are resistant to SOD, especially in areas where it is present. Resistant plant species and varieties are being researched. Some plants that resist infection include grasses, most conifers, alders and white oaks.
Some Rhododendrons that have shown very low infection rates include:
- Rhododendrons ‘PJM’, ‘Purple Splendor’, R. yakushimanum ‘Ken Janeck’
- Rhododendron (Azaleas) ‘Girard’s Fuchsia’, ‘Girard’s Rose’, ‘Gloria’, ‘Hino Crimson’, ‘Macrantha’, ‘Inga’, ‘Marilee’, R. arborescens, R. carolinianum, R. macrosepalum, R. viscosum
Jay Pscheidt, Oregon State University
Water Management
P. ramorum (SOD) and other Phythophthora species thrive in wet conditions. Improve drainage so plant roots are not in standing water.
- Don’t over-water.
- Plant in raised beds.
- Place pots on well-drained surfaces.
- Break up compacted soil that blocks drainage.
- Use drain tile to remove excess water.
Avoid overhead irrigation that will leave wet foliage. Space plants apart so their canopies can air dry between watering.
"Fertiliser Bags" by chuckoutrearseats is licensed under CC BY-SA 2.0
Don’t Over-fertilize Plants
- Excess nitrogen makes foliage more succulent and prone to infection.
Watch for Infected Plants
- There is no cure for SOD, so prevention is essential.
- SOD is most often detected where residential neighborhoods and wild areas intermingle.
- There are different methods to deal with infected plants if you live in or out of an SOD-quarantined area. For complete information see: Sudden Oak Death: Prevention, Recognition, Restoration.
Solutions for SOD
Early Detection: Report New SOD Locations
Watch for infected plants on the south coast of Oregon. Look for SOD on your property and places in SW Oregon that you visit.
Sanitation, Physically Remove Plants
If a P. ramorum infection is confirmed by a lab test, remove and destroy the infected plant, and nearby host plants that may have become infected.
Fungicide
There are no treatments that can cure Sudden Oak Death. One fungicide product can provide some protection.
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 Early Detection and Reporting |
Effective |
Low risk |
Recommended |
B Physical Removal |
Effective |
Low risk |
Recommended |
C Prevent with Fungicide |
Somewhat effective |
Moderate risk |
Recommended |
|
D If Using Fungicides, Protect Yourself & Minimize Risks
|
A
Early Detection and Reporting
Non-Chemical Method
Oregon Dept. of Forestry
Early Detection and Reporting
Recommended
The SOD fungus can only be accurately identified in a lab. If you see host plants with symptoms that look like SOD, AND if you are outside of known infested areas:
- Use your smartphone, GPS, or maps program to get the latitude and longitude of the plant.
- Take clear, close-up digital photos. Include: The plant part with symptoms, the whole plant, and the general area where the plant is located.
- Contact the following resources for further instruction.
In Curry County:
Oregon Department of Forestry, 541-469-5040
ODF Website https://www.oregon.gov/odf/Pages/index.aspx
Outside of Curry County:
Oregon Department of Forestry, Forest Health Dept., 503-945-7200.
Forest Health Unit Website https://www.oregon.gov/ODF/ForestBenefits/Pages/ForestHealth.aspx
| Does it work? | Effective |
| How much effort? | Moderate effort |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
B
Physical Removal
Non-Chemical Method
"A pile of freshly cut firewood" by Ivan Radic is licensed under CC BY 2.0
Physical Removal
Recommended
- Removing a diseased plant prevents the spread to neighboring plants.
- Infected branches, twigs, and leaves can spread SOD even if they have fallen or been pruned off.
- If infected trees are cut down, use the wood on site, for firewood, wood chips, or mulch.
- Don’t move the wood and other tree parts to disease-free areas. If you must remove infected plant material, bag it and send it to a landfill.
| Does it work? | Effective |
| How much effort? | High effort
|
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
C
Prevent with Fungicide
Chemical Method: Use with caution
Prevent with Fungicide
Recommended
Sample product label with Active Ingredient(s) highlighted
A red box on the example label highlights active ingredient Mono- and di-potassium salts of Phosphorous Acid. Check the label for use against Sudden Oak Death.
| Does it work? | Somewhat effective There are no treatments that can cure sudden oak death after a plant is infected. One fungicide product is approved for homeowner use. It can help protect high-value tanoaks and oaks from infections. It can also slow down the growth of the disease in the plant. |
| How much effort? | Moderate effort |
| What's the risk? | Moderate risk Using fungicides comes with real risks. ALWAYS read the entire label front to back. Review instructions even for brands you know. |
| Possible risk of exposure or harm from chemicals | Using fungicides includes some amount of risk. The lowest risk comes with using alternative methods. You may be exposed to a fungicide if you:
Follow directions closely to reduce risk. |
One product is available for home use. The active ingredient is Mono- and di-potassium salts of Phosphorous Acid. Look for this chemical names in the “Active Ingredients” section of product labels.
Garden-phos, the suggested fungicide, is listed in the Pesticide Information Center Online (PICOL) Database. It is 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.
Fungicide Application Tips
- Fungicide products work best when applied before plant diseases get started. Good management practices should also be used.
- The compound can be injected into the tree. Or, it can be mixed with a surfactant and sprayed on the trunk. It will be absorbed through the bark.
- It will need to be re-applied every 1 to 2 years as it wears off. Check for precise application timing on the label.
- Using fungicides comes with real risks. ALWAYS read the entire label front to back. Review instructions even for brands you know.
- Consult a commercial pesticide applicator for treatment of trees over 10 ft. tall.
If Using Fungicides, Protect Yourself & Minimize Risks
Chemical Method: Use with Caution
Weston Miller, Oregon State University
Why is it important to read fungicide 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 may be applied.
- Be precise in your application. More is not better.
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. It includes appropriate personal protective gear and application methods. 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 right protective gear. This often includes, but is not limited to: a long-sleeved shirt, pants, socks, closed shoes, safety glasses, and chemical-resistant gloves.
- 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 the 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.
Invasive Species Alert
- Invasives are non-native species that spread aggressively and alter the environment.
- Learn about Sudden Oak Death in Oregon. See Sudden Oak Death: Prevention, Recognition, Restoration
- An infected plant is most likely to have SOD if it is growing among infected plants. Also if the species is very susceptible to SOD.
Reporting SOD Locations
Phytophthora ramorum can only be accurately identified in a lab. If you see symptoms that look like SOD, on host plants outside of known areas of a SOD infestation:
- Use your smartphone, GPS, or maps program to get the latitude and longitude of the plant
- Take clear, close-up digital photos. One of the plant part with symptoms. One of the whole plant. One of the general area where the plant is located.
- Contact the following resources for further guidance.
In Curry County:
Oregon Department of Forestry. 541-469-5040
Outside of Curry County:
Oregon Department of Forestry, Forest Health Dept., 503-945-7200
or your local Oregon State University Extension office. Find it here: http://extension.oregonstate.edu/find-us
Invasive species data @ 2022, iMapInvasives (NatureServe)
View Larger Map >
If you find signs of sudden oak death in Oregon, please report it.
Content developed by Signe Danler and Thomas Jima. Pesticide safety information edited by Kaci Buhl.
Peer review facilitated by OSU Department of Horticulture.
SUDDEN OAK DEATH REFERENCES
Sudden Oak Death: Prevention, Recognition, Restoration (pdf)
Oregon State University Extension Service
Tanoak (Notholithocarpus densiflorus)-Sudden Oak Death
Oak (Quercus spp.)-Sudden Oak Death
Rhododendron-Ramorum Leaf Blight and Shoot Dieback
PNW Pest Management Handbooks
Sudden Oak Death
Gallery of SOD Plant Symptom Photos
California Oak Mortality Task Force
Sudden Oak Death
University of California IPM Center
Sudden Oak Death Guidelines for California Landscapers & Gardeners (pdf)
Sudden Oak Death Information for Homeowners (pdf)
California Oak Mortality Task Force