Brassicaceae (cruciferous) weeds

Diseases


(Click on photo to enlarge)

General Disease Management in Cruciferous Weeds

  • Crucifer Disease Guide (pdf) – A Practical Guide for Seedsmen, Growers and Agricultural Advisors. Published by Seminis Vegetable Seeds, Inc.’s Plant Health Department and Seed Health Departments.

Diseases

Black Leg

Disease: Black leg
PathogensPhoma lingam (sexual stage = Leptosphaeria maculans)
Host crops: Most members of the Brassicaceae (Cruciferae) = cabbage family, including broccoli, Brussels sprouts, cabbage, canola, cauliflower, various Chinese brassica vegetables, collard, kale, mizuna, mustard, oilseed rape, oilseed turnip rape, rutabaga, turnip, etc.), Sinapis (white and yellow mustard), and Raphanus (daikon and radish). Several wild species exist that may be infected by P. lingam including Descurainia (tansymustard), Sisymbrium (hedge mustard), and Thlaspi (penny-cress). This is a quarantine disease in six counties in northwestern WA and all counties east of the Cascade Mountains because of the risk of this pathogen to the brassica vegetable seed industry.

hypocotyl infection with pycnidia
Black leg symptoms on a cabbage seedling grown from an infested seed lot. Note the small, black fruiting bodies (pycnidia) on the hypocotyl of the seedling.
Photo Source: Lindsey du Toit, Washington State University
Black leg infection of a cabbage seedling
Black leg infection of the cotyledon of a cabbage seedling grown from an infested seed lot. Note the small, black fruiting bodies (pycnidia) on the cotyledon.
Photo Source: Lindsey du Toit, Washington State University
growout trial – cotyledon symptoms on a brassicaceae plant
Pycnidia of Phoma lingam on the base of the stem of a Brassica rapa plant, showing pink cirrhi oozing out of each pycnidium, containing thousands of conidia. The conidia are readily splash-dispersed.
Photo Source: Lindsey du Toit, Washington State University
Black leg symptoms at stem of an infected plant
Black leg lesion at the base of the stem of an infected plant from a Brassica rapa seed crop. Note the small, black pycnidia embedded in the lesion.
Photo Source: Cynthia Ocamb, Oregon State University
Phoma leaf spot – Cindy Ocamb
Phoma leaf spot lesion with tiny, black pycnidia present in the necrotic, circular lesion, surrounded by a narrow, chlorotic (yellow) halo.
Photo Source: Lindsey du Toit, Washington State University
Phoma lingam seed assay
Black pycnidia of the black leg fungus, Phoma lingam, on an infected cauliflower seed. Note the amethyst-colored cirrhi (gelatinous matrix) oozing from the pycnidia, which indicates the strain of the pathogen is virulent (able to cause Phoma leaf spot or black leg of brassicas).
Photo Source: Lindsey du Toit, Washington State University

On-Line Resources:

Addressing Blackleg in the Willamette Valley: Oregon Department of Agriculture permanent ruling released on black leg of brassicaceae in January 2015 – see the Brassica Production Districts document, and the OSDA Permanent Ruling document titled ‘Crucifer blackleg disease requirements moved into one regulation; removes same requirements from rapeseed production districts,’ below.

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Black rot

Disease: Black rot
PathogensXanthomonas campestris pv. campestris
Host crops: Most members of the Brassicaceae (Cruciferae) = cabbage family, including broccoli, Brussels sprouts, cabbage, canola, cauliflower, various Chinese brassica vegetables, collard, kale, mizuna, mustard, oilseed rape, oilseed turnip rape, rutabaga, turnip, etc.), Sinapis (white and yellow mustard), and Raphanus (daikon and radish). Most wild species can be infected by this pathogen. This is a quarantine disease in parts of six counties in northwestern Washington because of the risk of this pathogen to the brassica vegetable seed industry.

symptoms of Cabbage black rot-1
Cabbage black rot symptoms of marginal chlorosis and v-shaped lesions extending into the leaf.
Photo Source: Mike Derie, Washington State University

symptoms of Cabbage black rot-5
Severe blackening of the veins of a cabbage leaf infected with Xanthomonas campestris pv. campestris.
Photo Source: Lindsey du Toit, Washington State University
symptoms of Cabbage black rot-2
Cabbage stem showing blackening of the vascular tissue caused by the black rot pathogen, Xanthomonas campestris pv. campestris.
Photo Source: Mike Derie, Washington State University
symptoms of Cabbage black rot-6
Wilting of a cabbage leaf infected with Xanthomonas campestris pv. campestris.
Photo Source: Lindsey du Toit, Washington State University
symptoms of Cabbage black rot-3
Dieback and wilting of cabbage plants following a severe outbreak of black rot.
Photo Source: Mike Derie, Washington State University

symptoms of Cabbage black rot-7
Symptoms of leaf spot caused by Xanthomonas campestris pv. armoraciae (left) and X. campestris pv. raphani (right), two bacterial pathogens closely related to the black rot pathogen, X. campestris pv. campestris.
Photo Source: Lindsey du Toit, Washington State University
symptoms of Cabbage black rot-4
Blackening of the veins of a cabbage leaf following inoculation with the black rot pathogen, Xanthomonas campestris pv. campestris.
Photo Source: Lindsey du Toit, Washington State University

Online Resources:

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Club root of brassica vegetables

Disease: Club root of brassica vegetables
PathogenPlasmodiophora brassicae
Host cropsBroccolicabbagecauliflower, brassicaceae (cruciferous) weeds, and radish.

below-ground symptoms of clubroot on roots
Below-ground symptoms of clubroot.
Photo Source: Lindsey du Toit

On-Line Resources:

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White rust

Disease: White rust
PathogenAlbugo candida

White rust on Brassicaceae (cruciferous) weed
Photo Source: D.A. Inglis

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please contact: Lindsey du Toit at dutoit@wsu.edu or at 360-848-6140.

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