No. 4/April 17, 1998
We have received very few calls in the past week about wheat virus problems. Traveling through northern Arkansas and southern Missouri and into Illinois about 10 days ago, I did not observe what appeared to be serious virus problems in fields. Some areas of wheat fields in northern Arkansas had discolored areas that could have been soilborne mosaic virus (SBMV), but my Interstate windshield scouting techniques did not permit time to accurately assess the situation in detail.
If soilborne mosaic virus is present, warmer weather will cause the symptoms to disappear. This virus is active in cooler soils and especially in low-lying areas where soils stay wet. The vector of SBMV is a fungus that prefers wet and cool soils. Symptoms are most prevalent during cooler periods and usually disappear when warm weather returns. Symptoms include yellowing or other discoloration of the leaves, and possible stunting of the plants. If warmer weather does not cause a change in the plant's appearance, then some other virus is present and further lab testing may be desirable to determine its identity. If the new growth is green and healthy, then the problem is usually SBMV. However, no control measures are available for viruses, beyond selection of resistant varieties.
H. Walker Kirby (firstname.lastname@example.org. uiuc.edu), Extension Plant Pathology, (217)333-8414