Plant Disease Management Handbook

Cause Xanthomonas campestris pv. campestris is 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. When spread by water, bacteria enter water pores (hydathodes) at leaf margins or occasionally through insect or other mechanical injuries.

By C. M. Ocamb

The storage root of a radish plant showing the small, dark, brownish-black discolored areas of vascular elements which indicate that a wilt disease is present.

Photo by Cynthia M. Ocamb, 2020.

A young radish plant showing foliar discoloration (yellowing of the leaves) and wilting due to a wilt disease.

Photo by Cynthia M. Ocamb, 2012.

Leaves of a radish plant with a wilt disease showing yellowing on one half of a leaf.

Photo by Cynthia M. Ocamb, 2011.

See:

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

Seed head of radish with a characteristic staghead.

Photo by C. M. Ocamb, 2006.

Image related to Radish (Raphanus sativus)-White Rust

A radish seed head more severely impacted with White rust.

Photo by Cynthia M. Ocamb, Oregon State University, 2011.

Closer view of pustules of Albugo. Note the Downy mildew sporulation in the upper left portion of this image. White rust and Downy mildew often occur together in Brassica seed fields.

Photo by Cynthia M. Ocamb, Oregon State University, 2012.

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Seed Crop, Crucifers (Brassica, Eruca, and Raphanus spp.) - White Leaf Spot and Gray Stem

By C. M. Ocamb

See:

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

By C. M. Ocamb

Image related to Radish (Raphanus sativus)-Downy Mildew

A daikon leaf with downy mildew.

Cynthia M. Ocamb, 2014.

A stem of a radish seed plant showing dark lesions due to downy mildew.

Photo by Cynthia M. Ocamb, 2020.

Note the white sporulation within the necrotic lesions on these radish seed pods.

Photo by Paul Koepsell, 1983.

Close-up of the downy mildew spores produced on daikon stems.

Photo by Cynthia M. Ocamb, Oregon State University, 2012.

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

By C. M. Ocamb

Cause Aphanomyces raphani, a fungus-like organism. The disease has been so severe in northwestern Oregon fields that the crop has been plowed under. The variety White Icicle is very susceptible. The fungus attacks primarily radish but also can infect many other crucifers.

Image related to Radish (Raphanus sativus)-Black Root

Note the necrotic areas on the roots.

Photo part of OSU Extension Plant Pathology Slide

Lesions are at first discolored, brown to bluish black then progresses to a blackened, constricted area.

Melodie Putnam, 1999.

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

By C. M. Ocamb

Image related to Radish (Raphanus sativus)-Black Leg

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

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 roots and are thought to actively infect the host.

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Aster - Yellows

Cause A phytoplasma that is transmitted by the sugar beet leafhopper, Circulifer tenellus. Daikon appears more susceptible than round red varieties. Seed yield losses of 30% to 40% are common and are estimated to range up to 95%.