Plant Disease Management Handbook

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Boxwood (Buxus spp.) - Boxwood Blight

Cause Fusarium oxysporum f. sp. perniciosum has been diagnosed a few times in Oregon by the OSU Plant Clinic. Soilborne fungus that is difficult to control. The cultivars Tryon and Charlotte are reported to be resistant.

Symptoms Leaf wilting and defoliation along with internal black streaks in the wood and eventually tree death.

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Maple (Acer spp.) - Nectria Canker

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Maple (Acer spp.) - Leaf Scorch

Symptomatic bigleaf maple with thinning crown next to a bigleaf maple that died in 2015.

Amy Ramsey, 2015.

Chlorotic tipped and small leaves of bigleaf maple next to healthy, large green bigleaf maples leaves.

Amy Ramsey, 2014.

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Camellia - Sooty Mold (Black Mold)

Note: Aphids are a common problem. Sooty mold fungi colonize the insect's excrement.

This leaf is covered with black powdery sooty mold growing on honeydew.

OSU Extension Plant Pathology slide Collection.

Cause Drought, heat stress, and excess sunlight may cause leaf scorch. In general, there is not enough water reaching the leaf margin to keep up with transpiration. An interruption of the vascular system, as with cankers, can also produce these symptoms. Salt damage may occur on plants growing near sidewalks due to winter use of de-icing products or from over-fertilization.

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Golden Chain (Laburnum spp.) - Fusarium Canker

A canker on this branch due to Phoma sp. but bark blisters were sterile.

OSU Plant Clinic image, 2006.

Section of a Linden branch

This canker was due to Fusarium lateridium and Phoma sp. on this Tilia cordata 'Greenspire'.

OSU Plant Clinic image, 2007.

Shoot dieback of pyramidal linden due to Pseudomonas syringae.

Larry Moore, 1986.

Cause The fungus, Athelia rolfsii (syn. Sclerotium rolfsii). This fungus has a very wide host range and has recently appeared in vegetable crops in western Oregon.

The plant in the middle has wilted and died due to southern blight. Located in Benton County Oregon.

Jay W. Pscheidt, 2016.

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Greenhouse Plants, Ornamental - Pythium Seed Rot, Damping-off, and Root Rot

This Hydrangea paniculata 'Great Star' had root, crown and stem rot due to Pythium sp. and Phytophthora sp.

OSU Plant Clinic image, 2011.

This 'Endless Summer' Hydrangea had root rot and dieback due to Pythium sp. and Phytophthora sp.

OSU Plant Clinic image, 2011.

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Tomato (Solanum lycopersicum) - Blossom-end Rot