I don't belive, but some virus can spread trough roots if they grow into eachother, or just simple contact. Some virus can spread with pollen, and some can be crystallize, and stay infectious for a long time. You can look for almost all of the plant infecting viruses here: http://www.agls.uidaho.edu/ebi/vdie/sppindex.htm If you click on a virus name you can see how it is transmitted, the hosts and non susceptible plants, and many other things as well. Regards, Janos Hungary, Z5a