Washington State University

Plant Clinic FAQs - Plant Problems

Frequently Asked Questions About Plant Problems

Where can I go to learn more about Phytophthora ramorum, the cause of Sudden Oak Death?
These links will help you learn more about the pathogen, Phytophthora ramorum, commonly referred to as Sudden Oak Death.

I have a rhododendron that is wilting and dying back. What is wrong with this plant?
Dying Rhododendron
Plant problems can have many causes. For example, wilting can be caused by not enough water or by too much water. Many other factors, such as environment, cultural care, and the presence of insects or disease, can affect the health of a plant.

You will need to provide adequate sample material and an extensive description of the problem in order to achieve an accurate diagnosis. See plant problems sampling instructions for further sample submission information.

I have a lot of problems with my flowering cherry tree in my yard in Western Washington. Every winter the blossoms die after budding out and in the summer many of the branches are dead with brown leaves clinging to the plant. What is happening to the tree?
Cherry Brown Rot Disease
The damage described sounds typical of the disease brown rot caused by the fungal pathogen Monilinia. If the problem is indeed brown rot, refer to the Hortsense site and from the menu bar, click "Ornamentals", then "Ornamental cherry", and then "Brown Rot". You can find more information on this disease as well as management recommendations. You will want to prune the tree both to remove dead branches and twigs (also the fungal inoculum that may be present in the lesions), and to increase air circulation and lower humidity in the canopy. Prune out all affected twigs several inches below the area of injury.

Sterilize your pruning tools between cuts using 10% bleach or 70% ethyl alcohol (less corrosive to tools than bleach) to avoid spreading the problem. If possible, avoid getting the leaves wet when watering the trees. Follow label directions carefully if using fungicides making sure that the product is labeled for ornamentals in the home landscape.

Every fall, the leaves on my large Western red cedar (Thuja plicata) in my yard start turning brown and I worry that I am about to loose it. But then in spring the tree looks very healthy, what is happening?
The red "flagging" branches observed on the healthy cedars in fall is normal leaf senescence. For information on what cedar flagging looks like refer to the WSU Hortsense web site and from the menu bar, click "Ornamentals", then "Cedar", and then "Cedar flagging". Double clicking on image should enlarge picture.

I planted an arborvitae hedge on my property line six years ago. The plants never really thrived and now it seems as if entire plants are dead. What could be wrong?
Failure to thrive and plant death often indicates root problems. Most arborvitae hedge problems submitted to the Puyallup Plant and Insect Diagnostic Laboratory appear to have a nonliving origin of damage (such as overwatering, poor planting technique, etc.) rather than having been caused by a disease or insect problem. Arborvitaes require excellent soil drainage and good air circulation around the plants. We would require more information, as well as a sample of a declining plant including root material, to help pinpoint the cause of your arborvitae hedge problem. British Columbia has an excellent bulletin discussing problems with "cedar" hedges. You can find this bulletin at Dying Cedar Hedges– What Is The Cause?

We recently had a large elm tree diagnosed with Dutch elm disease. We are unable to burn the tree. How can be best dispose of the plant to prevent the disease from spreading to other elms?
Dutch Elm DiseaseChipping wood into small pieces (below 1 -1 1/2 inches) that will quickly dry out would probably be a suitable alternative to burning. The fungal pathogen, Ophiostoma ulmi, should die as the wood dries.

The main trunk wood should be debarked to prevent the invasion of bark beetles (carriers of the Dutch elm disease fungus). Beetles do not feed or lay eggs in or on wood chips, or other wood, once the bark is removed.

You could probably also contact your city or county and get a special burning permit since you are working to stop the spread of the disease.

Puyallup Research and Extension Center, 2606 West Pioneer, Puyallup WA 98371-4900, 253-445-4500, Contact Us