Blackleg

HOSTS

  • Brassicas

DESCRIPTION

Blackleg, or stem canker, in brassica crops is caused by the fungus Phoma lingum.

BIOLOGY

Phoma lingum can be spread through the use of infected seeds, and crop debris. Additionally, contact with contaminated water, tools, or wind-dispersed spores can introduce the pathogen to new hosts.  

The fungus can invade a plant through the stomata or pre-existing wounds. Once inside the host plant, P. lingum will survive on the contents of the plant’s cells while colonizing the foliar, stem, and crown tissues. Lesions containing the fungi’s fruiting bodies can appear on the leaves and crown. The leaf spots will be light brown and circular, while the lesions on the crown will be dark-colored and sunken. Growth of the stem lesions can cause the stem to be girdled or broken.

SYMPTOMS

  • Discolored lesions on plant stem 
  • Tan, oval-shaped leaf spots on foliage 
  • Black streaks in vascular tissue of the stem

GENERAL MANAGEMENT

  • Use certified disease-free seeds 
  • Remove infected plants and plant debris 
  • Rotate with unsusceptible crops 

 

Precautionary Statement: Utah State University and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document. All pesticides are labeled with ingredients, instructions, and risks, and not all are registered for edible crops. “Restricted use” pesticides may only be applied by a licensed applicator. The pesticide applicator is legally responsible for proper use. USU makes no endorsement of the products listed in this publication.