Forages: Bacterial Wilt

Excerpt from Agronomy Guide for Field Crops (Chapter 5)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Incidence
2. Appearance
3. Disease Cycle
4. Management Strategies
5. Updates on Forages: Bacterial Wilt
6. Related links...

Incidence

Bacterial wilt has historically been one of the most important forage diseases not only in Ontario but anywhere they are grown. The development of resistant varieties has made the disease less common.

Appearance

Symptoms become apparent as the stand gets older (3 or more years). Infected plants are stunted and have a yellow-green colour. In severe cases, the plant has spindly stems with small, distorted leaves. Infected plants that are stressed by water, heat or both will wilt or die and are scattered throughout the stand. Infection stresses the plant and increases its susceptibility to winterkill. Cutting the taproot in half (in cross-section) will show a light brown-to-yellow discolouration of the vascular tissue near outer edge.

Disease Cycle

This disease is caused by a soil bacteria that survives in diseased alfalfa roots and in plant debris for at least 10 years. Infection occurs through wounds to the roots and crown or through cut stems. The bacteria causes the plant to wilt since it grows in the water-conducting tissue (vascular system) of the plant, thereby blocking water and nutrient movement in the plant.

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Management Strategies

All recommended varieties are resistant to the disease. Since the bacteria can be spread through wounds, it is recommended to cut young, less-susceptible stands first and then move to older stands. Stands should be cut when the plants are dry. This will limit or reduce potential spread from infected to non-infected plants. The bacteria can be spread in seed and hay.

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Updates on Forages: Bacterial Wilt

No updates available at this time.

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Related links...

• Diseases
• Forages
• Field Crop Protection Guide - Publication 812

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