Plant Disease Management Handbook

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Hawthorn (Crataegus spp.) - Rusts

Close up of aecium on underside of leaf.

Robin Rosetta, 2011.

Just a few spots of rust on these quince leaves.

Joseph Postman, 2008.

Rust infection results in misshapen fruit.

Jay W. Pscheidt, 2012

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Hawthorn (Crataegus spp.) - Leaf Spot

Photinia - Leaf Spot

Leaf spot caused by Entomosporium sp.

OSU Extension Plant Pathology Slide Collection, 1974.

Powdery mildew on quince.

Joseph Postman, 2008.

Fabraea leaf spot on quince.

Joseph Postman, 2008.

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Cherry (Prunus spp.) - Brown Rot Blossom Blight and Fruit Rot

Quince (Cydonia oblonga) - Fire Blight

Closeup on flowers that have died back but not fallen off. Sporulation of the fungus can be seen as a gray cast to the dead flower parts.

Jay W, Pscheidt, 2008.

Image related to Quince-Brown Rot Blossom Blight

Blossom blight occurs during bloom when temperatures during rainfall are over 50F.

Jay W. Pscheidt, 2012

Cause Venturia inaequalis (formerly Spilocaea pyracanthae), a fungus that overwinters in infected leaves, twigs, and berries. No ascigerous state has been identified. Hosts are evergreen, but only young leaves and berries are most susceptible to infection. Rain splashes spores to young, emerging leaves and flower buds in the spring. Conidia, produced in lesions, are also spread during wet weather to healthy portions of the plant. Wet weather favors disease development.

Note the necrotic areas on the fruit.

OSU Extension Plant Pathology Slide Collection, 1957.

Image related to Pyracantha (Firethorn)-Scab

Lesions look just like scab on apples.

Jay W. Pscheidt, 2012.

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Fire Blight of Apple and Pear

Pear (Pyrus spp.) - Fire Blight

Image related to Pyracantha (Firethorn)-Fire Blight

Dieback due to fire blight.

OSU Extension Plant Pathology Slide Set.

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Squash (Cucurbita spp.)

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Peach (Prunus persica) - Shothole

Note the holes in the leaves both along the margins as well as in the leaf blade.

Jay W. Pscheidt, 2016.

Shothole symptoms are more obvious near the base of this plant.

Jay W. Pscheidt, 2018.

Image related to Prunus laurocerasus-Leaf Spots and Shothole

Leaf spots and shothole on English Laurel due to Pseudomonas.

Melodie Putnam, 2009.

Leaf spots and shothole due to the fungus Wilsonomyces carpophilus.

OSU Plant Clinic collection, 2012.

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Cherry (Prunus spp.) - Nematode, Dagger

Cherry (Prunus spp.) - Stem Pitting

Image related to Prune and Plum (Prunus spp.)-Virus Diseases (Tomato Ringspot)

The bark has been stripped away from the graft union so we can see the poor wood development on the rootstock due to Tomato Ringspot.

OSU Extension Plant Pathology Slide Set.

Note the yellower and skinier leaves on left branch with Prunus necrotic ringspot virus.

Photo by Jay W. Pscheidt, 1996.

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Cherry (Prunus spp.) - Silver Leaf

The top branch has leaves that are a much lighter color than leaves on lower branch.

Photo by Jay W. Pscheidt, 1994.

Image related to Prune and Plum (Prunus spp.)-Silver Leaf

Branch showing silver leaf symptoms on the left and normal branch on the right.

Jay W, Pscheidt.

Branch showing silver leaf symptoms stands out from all the other branches.

Jay W, Pscheidt.

Cause Tranzschelia discolor and T. pruni-spinosae, fungi widespread in prunes and plums. Rust has been considered a curiosity rather than a problem in Oregon; however, rust may be severe some years in prune plantings in western Oregon. The alternate host is Anemone sp.

Upper side of leaves show angular chlorotic spots while lower leaves are showing black telia.

Jay Pscheidt, 2006.

Many leaf spots can show up late in the year.

Jay Pscheidt, 2006.