Plant Disease Management Handbook

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Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Powdery Mildew

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Maple (Acer spp.) - Sooty Bark Disease

Maple (Acer macrophyllum) - Brittle Decay

Oak (Quercus spp.)-Inonotus Root and Butt Rot

Limb and/or trunk failure due to fungal wood decay is a common problem with old big leaf maples.

Jay W. Pscheidt, 2015.

Although wood decays generally lead to limb breakage and/or uprooted trees during wind or ice storms, this tree came down unexpectedly one calm spring morning.

Jay W. Pscheidt, 2020.

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Maple (Acer spp.) - Bleeding Canker

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Maple (Acer spp.) - Bacterial Leaf Spot and Dieback

Maple (Acer spp.) - Nectria Canker

Phomopsis sp. found in this sunken canker on this red 'Sunset' maple.

OSU Plant Clinic image, 2015.

Phomopsis sp. found in this canker at the node of Acer palmatum.

OSU Plant Clinic image, 2016.

The discoloration here is due to Cytospora sp. on this Acer japonica.

(Note that Verticillium was also found in this tree.)

OSU Plant Clinic image, 2013.

The surface of Cytospora cankers develop raised pycnidia and in humid weather, amber to orange, hair-like spore tendrils can be seen extruding from the pycnidia.

Phil Hamm, 1991.

Canker on Japanese maple due to Diplodia mutila.

OSU Plant Clinic Image, 2017.

Several tree squirrels will strip the bark from late spring to early summer using the tender cambial layer for food and/or shredded bark for lining of nests.

Jay W. Pscheidt, 2015.

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Oak (Quercus spp.) - 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.

Big leaf maple with Armillaria sp. mycelial fans.

OSU Plant Clinic image, 2010.

Solid mycelial plaque on on this big leaf maple.

OSU Plant Clinic image, 2012.

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Apple (Malus spp.) - Storage Problems

The tiny black dots on this stem are pycnidia within the canker on Manchurian crabapple.

Parama Sikdar, 2015.

Image related to Crabapple (Malus spp.)-Twig Dieback and Canker

Note dark sunken canker on one the crabapple branches on the right side of this image.

Parama Sikdar, 2015.

Mummified crabapple with pycnidia.

Parama Sikdar, 2015.

Unpruned Manchurian crabapple with mummified crabapple and pendant infected limbs.

Parama Sikdar, 2015.

Cause Five different viruses have been reported to infect cannas including bean yellow mosaic virus (BYMV), canna yellow mottle virus (CaYMV) , canna yellow streak virus (CaYSV), cucumber mosaic virus (CMV), and tomato aspermy virus (TAV). Cannas from the PNW positive for potyvirus (BYMV and/or CaYSV) and CaYMV have been diagnosed by the OSU Plant Clinic. CaYSV and CaYMV are common worldwide and affect plant health. Although specific vectors have not been determined, most of these are generally aphid-transmitted.

This 'Tropicana' canna with chlorotic leaf streaking hadCanna yellow mottle virus. Virus infection in stripped cultivars results in a messy pattern made of wide, irregular stripes and spots rather than the normal steady pattern of narrow stripes.

OSU Plant Clinic Collection, 2014.

This 'Bengal Tiger' canna with necrotic leaf stippling had a Badnavirus and possible other viruses.

OSU Plant Clinic Collection, 2007.

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Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Powdery Mildew

Cause The fungus, Erysiphe cruciferarum (syn. E. polygoni), can infect most crucifer crops and cruciferous weeds, but strains exist that have specificity and will infected only a subset of the crucifers. Older leaves are more susceptible to powdery mildew than younger leaves. Stressed plants will be more susceptible to disease.

Cause The fungus, Erysiphe cruciferarum (syn. E. polygoni), can infect most crucifer crops and cruciferous weeds, but strains exist that have specificity and will infected only a subset of the crucifers. Stressed plants will be more susceptible to disease. The fungus survives on infected hosts or as chasmothecia (formerly cleistothecia), sexually-produced survival structures on infected crop debris.