Plant Disease Management Handbook

Cause A bacterium, Pseudomonas syringae pv. apii, that overwinters in celery refuse and on celery seed.

Symptoms At first, a water-soaked spot appears on leaves and becomes bright yellow. The center of the spot gradually turns into a brown, necrotic spot with a yellow halo.

Cultural control

Image related to Celery (Apium graveolens var. dulce)-Bacterial Leaf Spot

Note some water-soaked spots on leaves with yellowish centers. Older spots are brownish with a yellow halo.

Photo by Stacey Fischer, 1990.

Cause Didymascella thujina, a fungus. Although the disease is found mostly in warm-moist environments typical of coastal low elevations of the Pacific Northwest, the pathogen is endemic to North America and found throughout the natural range of western red cedar. Spore discharge from wetted apothecia begins in late spring and increases gradually during the summer, reaching a peak between late August and early November.

This Thuja x 'Steeplechase' has leaf blight where the apothecia are embedded in leaf tissues which have dropped out leaving deep pits.

Geoff Stodola, 2021.

Many lower needles can become diseased.

Jay W, Pscheidt, 2008.

Image related to Cedar, Western Red (Thuja plicata)-Leaf Blight (Keithia Blight)

Light-brown to tan spots appear on the leaves, and large brown fruiting structures of the fungus (apothecia) form in the center of these spots.

Photo by Ralph S. Byther

Cause Pseudocercospora thujina (formerly Stigmina thujina) causes a common fungal blight on Port Orford cedar (POC). Seedstock collected from watersheds nearest to the coast, from more northern latitudes, and lower elevations developed less severe symptoms.

Image related to Cedar, Port-Orford (Chamaecyparis lawsoniana)-Stigmina Blight

Chlorosis and defoliation of needles first appear on the lower and interior branches and proceed upward and outward.

Danielle Martin

Dead foliage is of various shades of brown to gray depending on how long it has been dead.

Danielle Martin

Symptoms of foliage blight of Lawson cypress caused by Pseudocercospora thujina (Stigmina thujina).

Jeff Stone, 2006.

See:

Cypress (Cupressus spp.) - Canker

Notes: Seiridium cardinale is the usual fungus but a different species of Seiridium may be involved with cankers of Port Orford cedar in Oregon.

Image related to Cedar, Port-Orford (Chamaecyparis lawsoniana)-Seiridium Canker

Seiridium canker on Port-Orford-Cedar. Tree has been inoculated with the fungus. Picture shows death of tissue above cankered stem.

Danielle Martin

Seiridium canker on Port-Orford-Cedar. Tree has been inoculated with the fungus.

Danielle Martin

Cause The fungus-like microorganisms Phytophthora lateralis and P. cinnamomi kill Port Orford cedar seedlings and trees. The disease was found in nursery stock in 1923 and has since spread throughout the Pacific Northwest, in the tree's native range, southwest Oregon, and in landscapes with extensive hedgerows. Spread into the southwest Oregon mountains has been slow but progressive.

Image related to Cedar, Port-Orford (Chamaecyparis lawsoniana)-Root Rot

The bark has been stripped off to show the cambium which becomes a reddish-brown color when infected. Also note the clear transition between infected and healthy cambial tissue.

Photo by Phil Hamm.

A hedge row of cedars dying one after the other. The middle tree died in 1997 after the flood of 96. The next one died in 98 and the end one died in 2000. The last one may die by the end of 2001. Ridomil was used twice after the 1st tree died.

Photo by Jay W. Pscheidt, 2000

Many trees in a row but some are missing

Hedge row of Port-Orford Cedars progressively dying due to Phytophthora root rot.

Jay W. Pscheidt, 1991.

The first indication of infection may only be discoloration of the foliage (right side).

Jay W. Pscheidt, 1997.

Single tree on a golf course showing crown discoloration and tree death.

Ryan Contreras, 2021.

Defoliation due to Phytophthora root rot.

Melodie Putnam, 1999.

See:

Fir, Douglas and True - Armillaria Root Rot

Notes: Armillaria root rot is a problem mostly in the forest. It could also be a problem in the landscape if trees are planted in new home sites recently cleared of native vegetation. Avoid wounding roots and overwatering in landscape settings.

See:

Spruce (Picea spp.) - Tip Blight

Dieback of this Atlas Cedar branch is due to the more common fungus Sirococcus conigenus. Symptoms are similar for other fungi that also cause a needle blight and twig dieback.

Photo by Melodie Putnam, 1993.

Kabatina on Blue Atlas Cedar. The bark on the branch has been cut away to show how the pathogen has come in through the foliage and into the branch causing a necrosis in the cambium.

Jay W, Pscheidt, 2000.

Image related to Cedar (Cedrus spp.)-Needle Blight

Cedrus atlantica 'Glauca Pendula' with Sirococcus.

Neil Bell, 2010.

Cedrus atlantica 'Glauca Pendula' with Sirococcus.

Neil Bell, 2010.

Cause Evergreen plants, including conifers and broad-leaf types, naturally shed some old foliage each year. Abies and Picea tend to have long needle retention times while Pinus tends to have a shorter retention time. Stress factors, such as insufficient water, hot winds, construction damage or other root disturbance, poor planting procedures, or recent planting can promote flagging.