Plant Disease Management Handbook

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Greenhouse Plants, Ornamental - Powdery Mildew

White superficial powdery colonies have developed on leaves and stems of this purple ninebark.

Jay W. Pscheidt, 2018.

Image related to Ninebark (Physocarpus spp.)-Powdery Mildew

Colony of powdery mildew (Podosphaera aphanis var. physocarpi) on ninebark.

OSU Plant Clinic Collection, 2011.

Colonies of powdery mildew on ninebark can be extensive and cover much of the leaf surface.

OSU Plant Clinic Collection, 2011.

Powdery mildew covered shoot is likely bud infection from last year.

OSU Plant Clinic Collection, 2011.

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Peach (Prunus persica)

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Greenhouse Plants, Ornamental - Gray Mold

Healthy on the left and Botrytis blight on the right.

Jay W. Pscheidt, 2019.

Sporulation of Botrytis on spent flowers.

Jay W. Pscheidt, 2019.

Water soaked and necrotic spots on petals before collapse due to Botrytis blight.

Jay W. Pscheidt, 2019.

Senescent leaves can also be attacked and become a source of spores.

Jay W. Pscheidt, 2019.

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Daffodil (Narcissus spp.)

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Heavenly Bamboo (Nandina domestica)

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Tanoak (Notholithocarpus densiflorus) - Sudden Oak Death

Image related to Myrtlewood (Umbellularia californica)-Sudden Oak Death

The symptom produced on this baylaurel, or myrtlewood, is just chlorotic leaf tips.

Photo by Everett Hansen

Cause The fungus Colletotrichum gloeosporioides has been found a few times by the OSU Plant Clinic. Young juvenile tissue is susceptible to infection while older mature leaves are resistant. A problem during unusually high rainfall years.

Symptoms Brown necrotic leaf blight as well as black leaf blights and twig dieback of new shoots.

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Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - White Leaf Spot and Gray Stem

By C. M. Ocamb

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Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Sclerotinia Stem Rot

By C. M. Ocamb

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

By C. M. Ocamb