Wheat Streak Mosaic Virus in Phillips County

Several samples of Wheat Streak Mosaic Virus (WSMV) have been found in Phillips County. The virus has been found mostly in winter wheat and some barley. The virus is spread by the wheat curl might. The might survives on green material over the winter such as hail damaged fields and unkept summer follow.

Symptoms of WSMV include yellowing of the leaf in a streak or stripe pattern. Severely affected plants appear yellow and become confused with nutrient deficiency. Symptoms may appear on the edge of the field first. However entire filed have been infected in the county this year. Infected plants can appear stunted but do not use water efficiently. Growth usually stops and few heads are formed. If infection occurs after tillering but before early jointing, grain can be formed.

The disease is carried by the wheat curl might. The mite over winter in the crown of a plant as eggs, nymphs, and adults. When the infected plants start to grow in the spring, the eggs get the virus from the plants. Mites only live on green tissue. Eliminating the green bridge stops the disease. Wind disperses the mites when they climb into the canopy. Mites can travel up to two 2 miles but ¼ mile is more probable. Do not plant winter wheat before October 1 or adjacent to or downwind to late maturing spring crops. Do not plant spring wheat or barley down wind of infected winter wheat.

WSMV was first noticed in Montana in 1954 on winter wheat. Since then there have been several major outbreaks of the disease in 1964, 1981, and 1994. Losses can be as high as 100%. Call the Extension Office if you have suspicion of the disease or want a field inspected.