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Bacterial wilt
Clavibacter michiganensis subsp. insidiosus
  • bacterial wilt
  • bacterial blight
  • root rot

Plant hosts
  • Major hosts: Lotus corniculatus (bird's-foot trefoil), Medicago falcata (yellow alfalfa), Medicago sativa (lucerne), Trifolium (clovers)

Infected plants are usually scattered throughout a stand and are easily detected by their yellow-green color and stunted growth. Mild symptoms consist of leaf mottling with slight cupping or upward curling of the leaflets and some reduction in plant height. Severely infected plants are stunted and yellow-green, with many spindly stems and small, distorted leaflets. Diseased plants are most evident in the regrowth after clipping.  Cross sections of the taproot show a yellowish-brown discoloration of the outer vascular tissue.  As the disease progresses, the entire vascular tissue discolors. When the bark is peeled away the vascular tissue is yellowish brown, in contrast to the white of healthy plants. Pockets of infection sometimes appear on the inner surface of the bark.
Symptoms of bacterial wilt
Image provided by J.D. Janse, Plant Protection Service, Netherlands

In nature, bacterial wilt can spread by wind dispersal of soil or contaminated drainage water.  The bacterium is easily spread from field to field by contaminated farm machinery.  International spread of the pathogen can occur through the shipping of infected seed or hay.

Geographic distribution
Bacterial wilt is found in Africa, Asia, Australia, Canada, Chile, Europe, Japan, Mexico, the Near East, New Zealand, and the United States.

Applicable regulations
There are no regulations for bacterial wilt.
Return to plant pathogen list.