Forages: Aphanomyces Root Rot

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: Aphanomyces Root Rot
6. Related links...

Incidence

Aphanomyces root rot has increased over the past 10 years in Ontario, especially in heavy, wet soils.

Appearance

Aphanomyces root rot causes symptoms on both seedlings and older plants. Infected seedlings are stunted and have yellow leaflets and cotyledons. Roots and stems are grey and water-soaked in appearance. Severely infected seedlings turn light to dark brown. Older or established plants that are infected are stunted and yellow and have a reduced root system. These symptoms are often confused with nitrogen deficiency. Regrowth of infected plants is slow following harvest and winter.

Disease Cycle

The fungus survives in the soil on infected plants or debris. For infection to occur, the soil must be saturated. Disease development is favoured when moderate to high temperatures occur (16°C-30°C or 61°F-86°F) during humid or wet conditions. Fields that are compacted or drain poorly are especially prone to the disease. Infection occurs as the plant emerges, so new seedings are most at risk. Risk declines somewhat with the age of the stand.

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Management Strategies

Aphanomyces root rot is best managed through resistant varieties. Since saturated soils are needed for disease establishment, improving soil drainage and reducing compaction will reduce the disease.

Updates on Forages: Anthracnose (Alfalfa) Northern Anthracnose (Red Clover)

No updates available at this time.

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Related links...

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

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