Plant Diseases
Wheat Diseases in Arkansas
Soilborne Viruses
Wheat soilborne mosaic and wheat spindle streak mosaic viruses are
transmitted to wheat by the soilborne fungus, Polymyxa graminis. Symptoms appear
in late February or March as stunted yellow plants. Upon close examination,
leaves usually show a yellow-green mosaic pattern. In some fields disease will
be limited to wet areas. However, under Arkansas conditions, the entire field
may be affected.
Both viruses survive in association with their fungus vector. Infection
usually occurs in the fall during periods of high soil moisture. The most severe
symptoms occur when seedlings are infected shortly after emergence. The viruses
multiply in plants during cool weather. Optimum temperature is about 60 F Virus
multiplication stops at temperatures above 70 F. Usually infected plants will
green up by the end of March as temperatures increase. However, infected plants
usually have fewer tillers, are shorter and yield less than healthy plants.
Resistant varieties are the only means of control. Fortunately, there are
several adapted, high-yielding resistant varieties available to Arkansas
growers. See Fact Sheet 2074, Arkansas Wheat Performance Tests and Variety
Selection, for variety ratings for soilborne viruses.
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