Barley Yellow Dwarf Virus Starting to Show

The number of calls concerning barley yellow dwarf and other viruses have been increasing as the wheat crop develops. The following table compares the most common viruses which affect wheat in the province.

Table 1. This table shows the difference between the most common viruses which affect wheat in Ontario

	Barley Yellow Dwarf	Wheat Streak Mosaic	Soil-Borne Mosaic	Spindle Streak Mosaic
When to expect first symptoms	6 to 8 weeks after growth begins in spring - yellow to reddish flag leaves	4 to 6 weeks after growth begins in spring	Early spring. 1 to 2 weeks after growth begins in spring. Cold spring can extend symptoms longer.	Early spring. 1 to 2 weeks after spring growth begins. Cold spring can extend symptoms longer.
Typical pattern in field	Random circular areas	Most noticeable along edges of fields or near volunteer wheat . Diminishs as you go into the field.	Often circular or oval areas, especially in wet areas or cool soils	More widespread in field than soil-borne mosaic.
Leaf symptoms	Leaf tips bright yellow on upper leaves, or reddish flag leaves -- most distinct	Bright yellow leaves with streaking patterns toward tips. Most prominent on upper leaves. Curling of upper leaves.	Pale yellow leaves with mosaic patterns	Yellow-green mottling dashes and streaks parallel with veins
Stunting	Some-but hard to identify; fewer tillers	Severe stunting from fall infections	Some stunting but also some recovery after warm weather	Mild stunting and fewer tillers
Other symptoms	Poor roots; susceptible to winter injury	Poor roots; wilting; prostrate tillers	Poor roots; winter injury	Poor roots; winter injury
Vectors	Several aphid species	Wheat curl mite Aceria tulipae	Fungus --Polymyxa graminis	Fungus --Polymyxa graminis
Conditions favoring infection	Long warm fall	Long warm fall. Early volunteer wheat from hail or other factors at harvest	Wet soil in fall. Cool temperatures in spring.	Wet soil in fall. Cool temperatures in spring.
Control	Resistant or tolerant varieties	Destroy volunteer wheat. Delay planting to "fly free date."	Soft red winter wheat varieties usually more tolerant than hard red winter wheat varieties	Resistant cultivars. Late planting.

Modified from University of Missouri.