It may be rare, but, yes, we do have soil borne mosaic virus infecting wheat in western Kansas this year.
It’s certainly not the end of the world because mostly the infection is confined to fairly small spots, generally in lower areas of the field. Wheat in these spots in often thinner, stunted, and, of course, quite yellow.
Erick DeWolf, K-State Extension plant pathologist, says infected wheat will often have a yield reduction of 10 to 30%. “I think we can expect the wheat to remain stunted and thin in these areas. Affected plants may also have reduced head size.”
DeWolf says the K-State diagnostic lab has received a number of samples with symptoms consistent with soil borne mosaic. “This includes TAM 111 and TAM 112.
“The good news is that most of the infections we are seeing now likely took place in the fall. Unlike wheat streak mosaic, the soil borne virus should not continue to spread to currently healthy wheat. And as temperatures warm up, the symptoms will become less obvious.”
K-State Extension wheat specialist Jim Shroyer says the virus is vectored by a soil fungus triggered by wet soils in the fall. “Thus, if you have a wet fall and if you have the fungus, you’ll get the disease. And once you have the fungus, you’ll always have it.
“Of course, the further east you go in Kansas, the greater the likelihood of having soil borne mosaic simply because it’s wetter back there. It is rare to see it in western Kansas, but certainly not impossible.”
Interestingly, Shroyer says the soil fungus can be transported from one area of the field to another by tillage, for instance, much in the same way that bindweed spreads. If a piece of bindweed rootstock that is one eighth of an inch in diameter and 2 inches long is dragged to a new location, it has everything it takes to produce a new plant.