Wheat Streak Mosaic

Washington State University Bulletin

SP0004 -- 1993

Diseases of Washington Crops.

Otis C. Maloy and Debra Ann Inglis

 

Small Grains Home * Wheat Diseases * Barley Diseases

Cause

Hosts

Symptoms and Signs

Disease Cycle

Control

1997 PNW Pesticide

Recommendations

Other interesting Wheat Streak Mosaic sites

Wheat streak mosaic, or yellow mosaic, is an occasional problem in Washington, particularly when a "green bridge" occurs between the current crop and the newly seeded crop. When present, wheat streak mosaic can cause serious losses.

Cause
Wheat streak mosaic is caused by a virus which only the wheat leaf curl mite, Acerina tulipae, transmits. This very small (about 0.3 millimeter long) eriophyid mite thrives on the lush, young growth of grasses. Its detection is helpful in diagnosing the disease. The mite is cigar-shaped, has no wings, and can be seen only with the aid of a microscope. It produces a fine web, which carries it on air currents. All stages of nymphs and the adult mite transmit the virus. It is not passed through eggs.

Hosts
Hosts include wheat, oats, barley, rye, corn, and other grasses; although some common weed grasses, such as quack grass, are not known as hosts. Reported hosts for the virus and the vector are not identical, but there is much overlap.

Symptoms and Signs
Wheat streak mosaic symptoms develop in the spring; diseased plants are stunted, and leaves are mottled with light green-yellow streaks (Photo 17). Fewer tillers form than is normal, and the heads may be sterile. Sometimes leaves are tightly rolled because mites feed preferentially on the upper leaf surfaces, and cause leaves to curl inward along the long axis.

Disease Cycle
The virus and mite can survive only a short time, 1 or 2 days, without a living plant. Therefore, infectious mites move from crops, volunteer plants or grasses approaching late maturity or senescence to the succulent seedlings of a recently seeded host, where they feed and transmit the virus. This host continuum, sometimes referred to as a green bridge or as green-on-green, often occurs where both spring and winter wheat are grown, when summer crops are late maturing, or if wheat is planted for livestock forage. The mites may need only 15 minutes to acquire the virus and can remain infective for up to 9 days.

Control
Cultural. No resistant commercial wheats are available. Avoid green bridges by delaying seeding and destroying volunteer wheat and perennial grass hosts.

References
Bruehl, G.W., and H.H. Keifer. 1958. Observations on wheat streak mosaic in Washington, 1955-1957. Plant Dis. Rep. 42:32- 35.

Shahwan, I.M., and J.P. Hill. 1984. Identification and occurrence of wheat streak mosaic virus on winter wheat in Colorado and its effects on several wheat cultivars. Plant Disease 68:579581.

Other Interesting Wheat Streak Mosaic sites:
North Dakota State University Extension Service, Wheat Streak Mosaic -- description and pictures

University of Kentucky College of Agriculture, WHEAT STREAK MOSAIC VIRUS AND THE WHEAT CURL MITE -- detailed descriptions and links to pictures.