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Discoloration of the xylem typifies Verticillium wilt.

Cole Crops

Verticillium Wilt

Pathogen: Verticillium dahliae

(Reviewed 6/07, updated 6/07)

In this Guideline:


SYMPTOMS AND SIGNS

The older, lower leaves of plants turn yellow and wilt. These leaves eventually turn brown and drop off the stem, usually when plants approach maturity. The water-conducting tissues (xylem) of the stems and roots become black. Overall growth of the plant may be stunted.

COMMENTS ON THE DISEASE

Verticillium wilt is usually a minor problem on cole crops. However, a more serious Verticillium problem occurs on cauliflower in coastal areas. Verticillium wilt symptoms are more prevalent on late summer and early autumn crops; cool soil temperatures favor infection and disease symptom development. The pathogen forms resistant structures (microsclerotia) that enable it to survive in soil for a decade or longer.

MANAGEMENT

Known infested fields should be planted to cauliflower only in winter or early spring. Some cauliflower cultivars may be more tolerant to Verticillium wilt than others. Avoid introducing the pathogen into clean fields. Planting broccoli, a nonhost of V. dahliae, may help reduce pathogen levels through a process called biofumigation: decaying broccoli residue, when disced into the soil, either gives off natural chemicals that can kill V. dahliae or alters the soil microflora so that V. dahliae survival is reduced.

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cole Crops
UC ANR Publication 3442
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
K. V. Subbarao, Plant Pathology,UC Davis, Salinas

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