Plant Disease Management Handbook

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Note the dead branch due to Phomopsis.

Photo by Jay W. Pscheidt, 1992.

Diaporthe-affected foliage develops small, black, fruiting bodies (pycnidia) and spore horns (cirri) can be seen under moist conditions.

Melodie Putnam, 1994.

Image related to Juniper (Juniperus spp.)-Twig Blight

Phomopsis causes dieback of the current year's growth only. Older tissue will not be affected.

Melodie Putnam, 2008.

Black fruiting bodies of the Phomopsis fungus may sometimes be found on the affected foliage. Microscopic examination of the fruiting bodies is necessary to distinguish them from those produced by non-pathogenic fungi which may be colonizing dead tissues.

Melodie Putnam, 2008.

Twig blight due to Kabatina.

OSU Plant Clinic collection, 2012.

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Cypress (Cupressus spp.) - Canker

Note This disease has been found just a handful of times on samples sent into the OSU Plant Clinic.

Image related to Juniper (Juniperus spp.)-Seiridium Canker

Juniper leaf blight due to Seiridium cardinale.

OSU Plant Clinic Image, 2013.

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Crabapple (Malus spp.) - Rust

Juniper (Juniperus spp.) - Pear Trellis Rust

Cedar apple rust is rare in the PNW and more likely due to other species of rust.

OSU Extension Plant Pathology Slide Set, circa 1950's.

Gymnosporangium nelsonii (and G. bethelii) may produce woody, round, to elongate, galls on juniper branches and small stems.

Melodie Putnam, 1996.

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Juniper Cultivar Susceptibility

Image related to Juniper (Juniperus spp.)-Phytophthora Root Rot

This 'Blue Chip' juniper has Phytophthora root rot resulting in branch dieback above ground and in the center of the plant.

OSU Plant Clinic Image, 2014.

Branches and roots dying from Phytophthora.

Melodie Putnam, 2010.

Note the off-coloration of plants on the top and left as compaired to green color of the healthy plant to the right. Infected plants fail to green up in the spring after winter dormancy.

Photo by Jay W. Pscheidt, 1990.

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Juniper (Juniperus spp.) - Rust

Notice the gelatinized telia of this rust fungus.

Photo courtesy of David Ormrod.

Image related to Juniper (Juniperus spp.)-Pear Trellis Rust

An unusually large rust gall of unknown type.

Photo by Melodie Putnam, 1996.

Cause Phoradendron juniperinum and P. densum. A parasitic seed plant, mistletoe depends on its host for much of its water and mineral nutrients. Fruit can be toxic to humans and livestock, but birds eat and disperse them to new trees. P. juniperinum belongs to the same genus as the mistletoe that affects oak but will not grow on oak or other conifers.

Image related to Juniper (Juniperus spp.)-Mistletoe (a True Mistletoe)

Several mistletoe bunches can be seen in this tree.

Photo by Amy Jo Waldo, 2002.

Mistletoe branches seem to radiate out in a sphere.

Photo by Amy Jo Waldo, 2002.

Mistletoe branches are similar to but different from the Juniper branches.

Photo by Amy Jo Waldo, 2002.

Seeds or fruits are round and have a pinkish color.

Photo by Amy Jo Waldo, 2002.

Cause 'Tam' (Juniper sabina 'Tamariscifola') and 'Pfitzer's' (Juniper chinensis 'Pfitzeriana') juniper often are deficient in magnesium, and other cultivars may be as well. Competition with calcium-rich growing medium or acid conditions can also produce magnesium deficiency when it is not limiting.