Plant Disease Management Handbook

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

By C. M. Ocamb

Image related to Broccoli (Brassica oleracea)-Downy Mildew (Staghead)

Heavily infected leaf.

Photo by Paul Koepsell, 1982.

Cause The fungi or fungus-like microorganisms, Pythium spp., Fusarium spp. and Rhizoctonia solani, attack young seedlings of many vegetables including members of the genus Brassica. These soilborne microbes can persist indefinitely in soil or plant debris. If seedlings are affected before emergence, it appears as poor germination.

Broccoli plants at various stages of Rhizoctonia infection of the lower plant portions.

Photo by the OSU Plant Clinic, 2023.

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

By C. M. Ocamb

Image related to Broccoli (Brassica oleracea)-Clubroot

Note the clubbing of the broccoli roots.

Photo by Cynthia M. Ocamb, 1998.

Transplant infected even before being set out in the field.

Photo by Melodie Putnam, 1997.

Healthy plants in the center and plants with club root on the right.

Melodie Putnam, 1997.

Healthy plant on the right and club root on the left.

Melodie Putnam, 1997.

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

By C. M. Ocamb

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

By C. M. Ocamb

Image related to Broccoli (Brassica oleracea)-Black Leg (Phoma Stem Canker)

Close-up of a leaf spot caused by Phoma lingam on a Brassica leaf. Note the tiny black dots which are the pycnidia.

Cynthia M. Ocamb, May 2014

Purple sprouting broccoli with a stem lesion due to black leg.

Cynthia M. Ocamb, Jan. 2015

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

Cynthia M. Ocamb, October, 2014

Cause The soft-rot bacterium, Pectobacterium carotovorum subsp. carotovorum (syn. Erwinia carotovora var. carotovora), enters through natural openings or wounds caused by insects and equipment. Pseudomonas spp. have been isolated from diseased heads and are thought to actively infect the host.

Image related to Broccoli (Brassica oleracea)-Bacterial Soft Rot Erwinia

Note the decay at the center of the head.

Photo by Kathy Merrifield.

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Broccoli (Brassica oleracea) - Bacterial Soft Rot Erwinia

Cause The bacterium, Pseudomonas syringae, is causing a new disease on broccoli. Though it hasn't been found in the Pacific Northwest, it has been described in California production.

Symptoms Large, angular lesions develop on leaves. At first, lesions are gray-green but then turn tan. Overhead irrigation is associated with numerous spots on each leaf.

Cultural control

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Fir, True (Abies spp.) - Rusts