Plant Disease Management Handbook

See:

Alder (Alnus spp.) - Collar Rot (Phytophthora Canker)

Rhododendron - Ramorum Leaf Blight and Shoot Dieback

Image related to Tanoak (Notholithocarpus densiflorus)-Sudden Oak Death

A good example of what happens when SOD infested sites are not treated promptly. The top image was taken in 2011 while the bottom image was taken in 2013. Recent mortality appears red while older mortality has become leafless.

Ebba Peterson, 2011 & 2013.

Tanoak trunk with weeping wounds typical of this fungal infection.

Photo by Everett Hansen

A tanoak sprout infected with SOD showing the darkened petiole symptom.

Ebba Peterson.

The first occurrance of Sudden Oak Death in Oregon was on these Tanoak trees. Note the brown trees in the center of the picture on the ridge.

Oregon Department of Forestry (Mike McWilliams)

Dead leaves on takoak from SOD.

Jared LeBoldus, 2017.

Poison Oak can also get this disease. Note the weepy areas on this branch.

Photo by Alan Kanaskie

See:

Oak (Quercus spp.) - Armillaria Root Rot

Cause The fungi Erysiphe platani (formerly Microsphaera platani) has been reported from Washington and Oregon. Conidia are released in response to abrupt decreases in relative humidity. Wind blows conidia to healthy foliage where they start new mildew colonies. Too much water, such as flowing water or rain, destroys spores by causing them to burst. The fungus does not grow in a leaf but rather across the surface.

White colonies of this fungus cause deformed leaves.

Jay W. Pscheidt, 1999.

See:

Maple (Acer spp.) - Leaf Scorch

Cause Apiognomonia veneta (asexual: Discula platani), a fungus that overwinters on infected sycamore twigs and dead leaves. Anthracnose is a common disease of the western sycamore, Platanus racemosa; the American plane tree, P. occidentalis, and the London plane tree, P. acerifolia.

Note the necrotic areas that follow the leaf veins.

Photo by Jay W. Pscheidt, 1994.

Death of terminal buds results in stimulation of dormant lateral buds, giving the tree a broom-like appearance.

Jay W. Pscheidt, 2018.

Defoliation due to anthracnose on sycamore.

Melodie Putnam slide collection, 1973.

Cause A fungus, Cladosporium variable, is believed to be the primary pathogen. This fungus can grow under a wide range of temperatures, but 59°F to 68°F with relative humidity above 80% is most conducive to disease development. Spores can be moved by air, rain splash, or equipment.

Cause The fungus-like microorganism, Peronospora farinosa f. sp. betae, causes disease on beet as well. The microorganism survives in infected crop residues and in wild or volunteer Beta spp. It also can survive in seed to a limited extent. Optimal temperatures for infection are 45°F to 59°F; little infection occurs above 68°F.

Cause Pythium spp. and Rhizoctonia solani are soil-infesting microbes that can build up rapidly and attack young germinating seedlings when soil is moist.

Symptoms Stems are attacked as young plants emerge. Plants wilt, fall over, and die. Germinating seed also can be attacked, rotting plants before they reach the soil surface.

Cultural control

Cause Likely the fungus Neoerysiphe galii since a dense mycelial mat is formed, but 3 different species of Golovinomyces also occur worldwide. Golovinomyces cichoracearum, has been reported for the PNW. These fungi are favored by conditions that produce high humidity but dry leaves. They are highly specialized pathogens that form close associations with hosts.

Image related to Sweet Woodruff (Galium oderatum)-Powdery Mildew

Powdery mildew can be extensive as seen on the plants on the left side of this image.

Jay W. Pscheidt, 2012.

Leaves may be entirely covered with the white powdery growth of this fungus.

Jay W. Pscheidt, 2012.

See:

Pea (Pisum sativum) - Root Rots