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Our Tan Oak Trees are at Risk

Sudden Oak Death (SOD) is caused by the pathogen Phytophthora ramorum. This plant disease can kill tanoak and black oak trees, but is not yet known to be present in the middle Klamath, which is at high risk of Phytophthora ramorum infestation by human caused and natural spread. This is due to the high frequency and abundance of tanoak and California bay laurel, which are the most important pathogen hosts for this disease.


The Oregon Department of Forestry recently estimated that the disease can travel three to five miles per year without human aid if left untreated. Currently, there are treatments in the two nearest infestations to help slow the disease, but their efficacy to slow the rate of spread is unknown. Even if this rate is reduced by 50%, the pathogen is likely to arrive by 2027. To prepare ourselves and our community, the Karuk Tribe, MKWC, UC Cooperative Extension, and the Forest Pathology lab at UC Berkeley are working together to hold outreach events and monitor streams and vegetation for the presence of this potentially devastating pathogen.

 

 How to Prevent Human Caused Introduction of SOD to the Mid Klamath

Phytophthora ramorum causing sudden oak death is an invasive pathogen that first arrived in California due to diseased nursery plants, likely ornamental rhododendrons. Since the initial human caused infections, it has spread aerially through the central and north coastal counties of California and Curry County in Oregon. The disease spreads by its spores. The spores are produced on the leaves of infected trees and can move several miles by air on the winds of spring storms. These spores also fall down on the under story and soil below the infected trees and can be moved by people in the intentional or unintentional transport of soil, wood chips, firewood or other gathered forest products.

You can follow these recommendations to prevent the human caused introduction of SOD into the Mid Klamath.

 
 

1. Know where the SOD infections are

Sudden oak death is present in the coastal counties of Central and Northern California, and Curry County in Oregon. If you know you are in an infected area you can take precautions to avoid unintentionally taking plant matter home with you. The map on the right is a general overview of infected areas and quarantined counties.

The closest infection to the Mid Klamath region is in Redwood Valley, on private property and in Redwood National Park. There is widespread infection in Southern Humboldt County in the Redway-Garberville area. See more detailed infection maps on the UCCE website.

There are heavy infection levels in the bay area as well as Southern Humboldt County. Marin County, Big Sur and Santa Cruz areas have been infected with SOD since the 1990s and have high levels of the pathogen. Please take appropriate sanitation precautions if you are visiting these areas.

The SOD map project and mobile app is a useful tool for determining the risk of SOD infection on a local scale. This app will show you if positive or negative samples have been taken nearby and show if you are standing in a high or low risk area.

 
 

 2. Know how to identify symptoms

The symptoms of SOD vary depending on infected species. Pepperwood and tanoak are the main vectors of the disease, so identification of symptoms on these trees is important for establishing whether or not you may be in an infected area. See the Symptom ID page for details on how to identify potential SOD infected host plants. SOD infection cannot be verified by field observation only, the only way to identify Phytophthora ramorum is in a lab. Samples can be sent to UCCE in Eureka, see their publication on how to identify and collect samples.

The best way to learn to identify the symptoms of SOD is through experience. The UC Berkeley Forest Pathology lab holds many SOD Blitzes through California every year, including those hosted by the Karuk Tribe in Orleans and Happy Camp.

The SOD Blitzes are communities coming together in the fight against Sudden Oak Death. SOD Blitzes inform the community about Sudden Oak Death, get locals involved in detecting the disease, and result in detailed maps of disease distribution.

For Gatherers: It is important to familiarize yourself with symptoms of the plant(s) you collect. First check to see if it is a host, and check what it's symptoms are. It is always important to collect healthy plants, moving around unhealthy plant material spreads plant diseases including SOD.

 
 

3. Sanitize

If you travel through a SOD infected area it is best to clean your boots and your vehicle before you return home. SOD can be carried in mud, especially on bits of plant material.

  • Clean your vehicle of accumulated leaf litter and mud. It is important to clean off this debris before you return home.

  • Clean boots and tools of any mud. You can use Lysol or a diluted bleach solution to disinfect your your shoes and tools.

  • Make sure no leaves or twigs are clinging to your clothing, hair, pets or livestock before you leave an infected area.

 
 

 4. Be cautious about potted plants.

Don't bring home that sad sick plant that was on sale at the nursery. Plants carry disease that can spread to other plants. Be especially cautious with rhododendron and camellia- they have an extremely bad track record for causing new outbreaks of SOD.

 
 

5. Know where your soil/wood chips/garden amendments are coming from

Plant material, including wood chips and forest products used to make soil can carry pathogens. It is important to know the source of your garden amendments to stay disease free.

Soil companies are not required to sterilize their products and it is difficult to trace the source of their ingredients. While it is not usual that commercial soils are carrying pathogens, it is a possible risk that can be avoided.

 
 

6. Keep Firewood Local

Moving firewood around spreads many forest pests, including SOD. It is best to burn firewood near where you gather it. If you are buying wood, know where it is coming from. Know where SOD infections are, do not bring firewood from an infected area to the Klamath River.

If you need to transport firewood long distances it is best to remove the bark at the cutting site and to keep it dry.

 

Plant Hosts of Phytphthora ramorum

The following plants are all hosts of the sudden oak death pathogen. Under normal conditions, P. ramorum does not kill most of these plants, with the exception of oak species and tanoak. Infected plants will display some sign of blight on leaves. These plants have potential to carry the disease, take care when gathering or moving these plants, including purchase from a nursery.

Native Plant Hosts

 

Trees

  • Bigleaf maple (Acer macrophyllum)

  • Black oak (Quercus kelloggii)

  • California bay laurel/Oregon myrtle (Umbellularia californica)

  • California buckeye (Aesculus californica)

  • California nutmeg (Torreya californica)

  • Canyon live oak (Quercus chrysolepis)

  • Coast live oak (Quercus agrifolia)

  • Coast redwood (Sequoia sempervirens)

  • Douglas-fir (Pseudotsuga menziesii)

  • Grand fir (Abies grandis)

  • White fir (Abies concolor)

  • Red fir (Abies magnifica)

  • Madrone (Arbutus menziesii)

  • Oregon Ash (Fraxinus latifolia)

  • Pacific yew (Taxus brevifolia)

  • Shreve's oak (Quercus parvula var. Shrevei)

  • Tanoak (Notholithocarpus densiflorus)

Herbs

  • Bead lily (Clintonia andrewsiana)

  • False Solomon's seal (Maianthemum racemosum)

  • Western starflower (Trientalis latifolia)

Ferns

  • California maidenhair fern (Adiantum jordanii)

  • Western maidenhair fern (Adiantum aleuticum)

  • Wood fern (Dryopteris arguta)

Shrubs

  • Azalea (Rhododendron occidentale)

  • Blueblossom (Ceanothus thyrsiflorus)

  • California coffeeberry (Rhamnus californica)

  • California hazelnut (Corylus cornuta)

  • California rhododendron (Rhododendron macrophyllum)

  • California honeysuckle (Lonicera hispidula)

  • Cascara (Rhamnus purshiana)

  • Evergreen huckleberry (Vaccinium ovatum)

  • Manzanita (Arctostaphylos manzanita, A. columbiana)

  • Kinnikinnick, bearberry (Arctostaphylos uva-ursi)

  • Labrador tea (Rhododendron columbianum)

  • Oregon grape (Berberis nervosa)

  • Poison-oak (Toxicodendron diversilobum)

  • Rhododendron (Rhododendron macrophyllum)

  • Salal (Gaultheria shallon)

  • Salmonberry (Rubus spectabilis)

  • Silktassle (Garrya elliptica)

  • Spicebush (Calycanthus occidentalis)

  • Toyon (Heteromeles arbutifolia)

  • Vine maple (Acer circinatum)

  • Wood rose (Rosa gymnocarpa)

 

Non-native, Ornamental and Horticultural Plant Hosts

 

  • Bilberry (Vaccinium myrtilus)

  • Camellia (various species and varieties)

  • Camphor tree (Cinnamomum camphora)

  • Cherry laurel (Prunus lusitanica, P. laurocerasus)

  • Chinese redbud (Cercis chinensis)

  • Daphniphyllum glaucescens

  • Drooping leucothoe (Leucothoe fontanesiana)

  • Euonymus kiautschovicus

  • European ash (Fraxinus excelsior)

  • European beech (Fagus sylvatica)

  • European yew (Taxus baccata)

  • Evergreen currant (Ribes laurifolium)

  • Evergreen Maple (Acer laevigatum)

  • Firethorn (Pyracantha koidzumii)

  • Goat willow (Salix caprea)

  • Griselinia (Grisselinia littoralis)

  • Holly (Ilex aquifolium, I. cornuta, I. purpurea)

  • Horsechestnut (Aesculus hippocastanum)

  • Japanese ardisia (Ardisia japonica)

  • Japanese Larch (Larix kaempferi)

  • Japanese oak (Lithocarpus glaber)

  • Kousa dogwood (Cornus kousa)

  • Lilac (Syringa vulgaris)

  • Lingonberry (Vaccinium vitis-idaea)

  • Loropetalum chinense

  • Magnolia (various species)

  • Mexican orange(Choisya ternate)

  • Mountain-laurel (Kalmia latifolia)

  • Myrtle-leafed Distylium (Distylium myricoides)

  • Ninebark (Physocarpus opulifolius)

  • Oleander (Nerium oleander)

  • Persian ironwood (Parrotia persica)

  • Pieris (various species and varieties)

  • Photinia, red tip (Photinia fraseri)

  • Red lotus tree (Manglietia insignis)

  • Rhododendron (all species, hybrids and cultivars)

  • Roble beech (Nothofagus obliqua)

  • Rose (specific cultivars and hybrids)

  • Rugosa rose (Rosa rugosa)

  • Scotch heather (Calluna vulgaris)

  • Scribbly gum (Eucalyptus haemastoma)

  • Spike witch hazel (Corylopsis spicata)

  • Strawberry tree (Arbutus unedo)

  • Striped bark maple (Acer davidii)

  • Sweet chestnut (Castanea sativa)

  • Sweet Cicely (Osmorhiza berteroi)

  • Star jasmine (Trachelospermum jasminoides)

  • Sycamore maple (Acer pseudoplatanus)

  • Tea olive (Osmanthus decorus, O. delavayi, O. fragrans, O.heterophyllus)

  • Viburnum (various species and varieties)

  • Victorian box (Pittosporum undulatum)

  • Wintergreen (Gaultheria procumbens)

  • Winter's bark (Drimys winteri)

  • Witch hazel (Hamamelis virginiana)

  • Yew (Taxus x media)

  • Various oak species of eastern U.S. and European origin

 

Symptoms of Sudden Oak Death

Pepperwood (CA bay laurel, Umbellaria californica) and tanoak (Notholithocarpus densiflorus) are the are the two local native plant species known to spread the pathogen Phytophthora ramorum. As such, they are the two most important species to watch for symptoms of SOD.

The best identification resource for the north coast is the symptom ID introduction by Humboldt County UC Cooperative Extension.

The Garbelotto lab at UC Berkeley has put together an ID sheet showcasing leaf symptoms on both pepperwood and tanoak.

To see symptoms on various other plants that host Phytophthora ramorum please see the hosts and symptoms page and the plant symptom photos at suddenoakdeath.org.

 

Pepperwood

Phytophthora ramorum causes a leaf blight on pepperwood and does not kill the tree. Look for dead leaf tips with yellowing behind a black line.

Tanoak

The disease often causes mortality in tanoak around two years after initial infection, but may take longer. Signs of infection include black lesions on the twigs, leaf die back originating in the petiole, dead branch tips, and bleeding cankers from the main tree stem.

 

Links

California Oak Mortality Task Force

Cooperative Extension Humboldt County - University of California

Forest Pathology Lab - University of California, Berkeley

Statewide Sudden Oak Death Quarantine - California Department of Food and Agriculture

Tribal Working Group - Western Integrated Pest Management Center

 

 Contact

For Tribal resource/gathering assistance:

Karuk Tribe Department of Natural Resources

Vikki Preston

Natural Resources Technician

vpreston@karuk.us

(530) 627-3446

General assistance:

Mid Klamath Watershed Council

Tanya Chapple

Plants Program Director

tanya@mkwc.org

(530) 627-3202

For symptom identification and sampling questions:

UC Cooperative Extension

Brendan Twieg

Staff Research Associate

bdtwieg@ucanr.edu

(707) 445-7351