Plant Disease Management Handbook

See:

Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Chlorotic Leaf Spot (Light Leaf Spot)

By C. M. Ocamb

Cause Xanthomonas campestris pv. campestris, a bacterium that overwinters in plant refuse for up to 2 years and is carried internally and externally on seed. The bacterium infects other crucifer crops and weeds. It may be spread in the field by water (rain, irrigation), insects, equipment, and animals. Many outbreaks can be attributed to disease spread in the seedbed.

Black rot infections of Kale starting at hydathodes.

Melodie Putnam collection, 1997.

See:

Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - Black Leg

By C. M. Ocamb

Image related to Kale (Brassica oleracea var. acephala)-Black Leg (Phoma Stem Canker)

A kale leaf with a leaf spot incited by Phoma lingam. Note the tiny black dots which are pycnidia.

Cynthia M. Ocamb, Dec. 2014

Kale seed crop with leaf spots due to the black leg pathogen.

Photo by Cynthia M. Ocamb, 2016.

Fresh market kale with Phoma stem lesions.

Cynthia M. Ocamb, Jan. 2015

The lower stem of a kale seed crop with black leg symptoms.

Cynthia M. Ocamb, May 2014

Close-up of Brassica crop residue colonized by Phoma lingam and Leptosphaeria maculans.

Cynthia M. Ocamb, October, 2014

Cause A bacterium, Pseudomonas syringae pv. maculicola, causes this disease, also known as bacterial leaf spot on cauliflower, broccoli, and Brussels sprouts. Bacteria survive on infested seed and crop residues as well as in soil. Cool, wet weather, common west of the Cascade Range, favors disease development before harvest in the fall.

Cause The phytoplasma 'Candidatus Phytoplasma phoenicium' subgroup 16SrIX-E has been associated with this problem. A witches' broom of western juniper (J. occidentalis) has been observed frequently in central Oregon. Trees with this problem seem to occur in known pockets. Affected trees do not have signs of rust or mistletoe.

Image related to Juniper (Juniperus spp.)-Witches' Broom

Stunted and densely packed shoots form this Witches' broom.

Melodie Putnam, 2007.

Stunted broom growth on top with normal branch growth on the bottom.

Melodie Putnam, 2009.

See:

Juniper Cultivar Susceptibility

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.

See:

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.

See:

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.

See:

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.

See:

Juniper (Juniperus spp.) - Rust

Pear (Pyrus spp.) - Trellis Rust (European Pear 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.