Cereals: Soil-Borne Wheat Mosaic Virus (SBWMV) Wheat Spindle Streak Mosaic Virus (WSSMV)

Excerpt from Agronomy Guide for Field Crops (Chapter 6)

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Table of Contents

1. Incidence
2. Appearance
3. Disease Cycle
4. Management Strategies
5. Updates on Cereals: Soil-Borne Wheat Mosaic Virus (SBWMV)
   Wheat Spindle Streak Mosaic Virus (WSSMV)
6. Related links...

Incidence

These two viruses are often easily confused with each other since the symptoms, life cycle and field pattern are similar. In certain cases, both viruses may be present in the same field.

Appearance

Typical symptoms of SBWMV on wheat leaves is a mosaic of green islands or blotches on a yellow background. Typical leaf symptoms of wheat spindle streak are yellow-to-light green streaks that are parallel to the leaf veins. The streaks are often tapered, which gives the lesions a spindle shape, hence the name. This is in contrast to soil-borne mosaic virus lesions, which are blotches. WSSMV can also cause stunting and reduced tillering in infected plants.

Disease Cycle

It is not uncommon to find that many plants are infected with both viruses since they share a common vector. The common link is a soil-borne fungus called Polymyxa graminis. The fungus produces zoospores (swimming spores) that invade root hairs and epidermal cells of young plants during periods of high soil moisture or in low, wet areas of the field. The virus is carried into the plant by the zoospores. The fungus can remain in the soil for at least 8 years. It is not as important to determine which of the two viruses is present as it is to determine that the symptoms are not due to other causes (fungal, bacterial, etc.). The first report of spindle streak mosaic in North America occurred in 1957, right here in Ontario. Fields at risk are those that have had several crops of winter wheat in the past 8-10 years. Yield losses range from less than 5% to 40%, but generally losses are low. Symptoms usually appear early in the spring when growth resumes. The optimum temperature for symptom development is 5°C-15°C (41°F-49°F).

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Management Strategies

Since the fungal vector for both viruses can survive for many years in the soil, crop rotation as a management option has had limited success. Fields that have had liberal amounts of poultry and livestock manures appear to reduce wheat spindle streak mosaic virus build-up.

Updates on Cereals: Soil-Borne Wheat Mosaic Virus (SBWMV) & Wheat Spindle Streak Mosaic Virus (WSSMV)

No updates available at this time.

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Related links...

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

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