Behavior of the Ordinary Tobacco Mosaic Virus in the Soil'

It is fairly evident that control of the ordinary tobacco mosaic disease {tobacco virus 1) (4)^ may be accomplished with considerable success through the application of all of a number of precautionary measures that have been recommended for the purpose. These measures are directed chiefly against introduction of the virus into the field from various sources where it may be harbored for long periods, and also against further dissemination of the disease once it has gained entrance into the crop. The means by which the virus, once introduced, is spread in the field are comparatively well understood and may be prevented in considerable degree. The relative importance of the various sources of initial infection is, however, not so clear. The multiplicity of ways in which the virus may persist for prolonged periods apart from the living tobacco plant renders the problem a complex one, requiring intensive study in its various phases. One phase of the problem in particular need of greater consideration than has been accorded to it relates to the harboring of the virus in the field soil. The present paper deals with the results of laboratory and greenhouse studies on the persistence and inactivation of the ordinary tobacco mosaic virus in the soil under various conditions. These investigations have shown that the virus may survive in soils for periods of 1 year or more, but that it is subject to relatively rapid inactivation under certain natural conditions. This inactivation is not suflScient, however, to eliminate soil infestation as a factor in tobacco mosaic infection, the more practical aspects of which it is proposed to discuss in a later contribution from this laboratory.