Plant Disease Management Handbook

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Holly (Ilex spp.) - Sooty Mold

Black fungal sooty mold growth all across this leaf.

Clebson Goncalves, 2025.

Insects on the underside of this leaf are responsible for the honeydew leading to sooty mold.

Clebson Goncalves, 2025.

Anything honeydew drips on gets covered with sooty mold including leaves, stems, branches, and nuts.

Clebson Goncalves, 2025.

Stem of 'Lewis' hazelnut with back sooty mold.

OSU Plant Clinic image, 2011.

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Geranium (Pelargonium spp.) - Botrytis Blight

Rhododendron - Cutting Rots

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Gladiolus - Fusarium Yellows and Corm Rots

Split corm of Freesia

Corm rot of this 'Red Beauty' freesia yielded both Fusarium sp. and Pythium.

OSU Plant Clinic image, 2013.

Cause The fungus Neonectria neomacrospora can cause a canker and dieback on true fir. Host species in the PNW where the pathogen has been detected include native species, such as Abies procera (noble fir), A. grandis (grand fir), A. amabilis (Pacific silver fir), A. lasiocarpa (subalpine fir), A.

By H. Fukada and L. J. du Toit

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Freesia - Corm Rot

Note Both Rhizoctonia and Fusarium have been found on corm rot samples by the OSU Plant Clinic.

Crocosmia bulb cut half longitudinally

Root and basal plate rot on these 'Limpopo' crocosmia which yielded both Rhizoctonia and Fusarium (as well as bulb mites).

OSU Plant Clinic Image, 2016.

Root and corm rot of this 'George Davidson' crocosmia yielded Fusarium.

OSU Plant Clinic image, 2015.

Cause The fungus, Fusarium oxysporum f. sp. corianderii, causes wilt and root rot of cilantro and has been reported in California, India, and South America. This strain of Fusarium can survive many years in soil in the absence of a cilantro crop.

Cause Alfalfa mosaic virus (AMV), which is transmitted by aphids and can be seedborne. This virus has a broad host range (attributed to multiple species of aphid vectors) and infects at least 430 species of 51 dicot plant families including alfalfa (some varieties are asymptomatic), beans, clover, pea, potato, and tomato. Cilantro plantings were found infected with AMV in western Oregon during 2017. Subsequent testing of samples of seed planted in affected cilantro fields showed AMV to be present in seed samples.

Cause Several organisms can cause lower stem and root rots on these holiday cacti including Fusarium oxysporum, Pythium spp., and Phytophthora sp. The OSU Plant Clinic has found Fusarium.

Stems on the right side of this holiday cactus have collapsed indicating lower stem and root rot. Also, note the flower buds on the left side of the plant that have developed late October to early November in response to the shorter day length.

Jay W. Pscheidt, 2022.

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Tree Wound Paints

Cut limb of this cherry branch shows the fruiting bodies of Trametes versicolor indicating wood decay.

Jay W. Pscheidt, 2015.

Wood decay can been considered when fungal fruiting bodies are observed on trunks and limbs.

Jay W. Pscheidt, 2008.