Geoff I was not talking about the disinfectant type virucides, I am talking about systemics that will infiltrate the cell and inactivate the virus. Plants have a very very effective mechanism called ''Gene Silencing'' when the plant 'learns' through certain chemical signals that there is viral infection it is able to modifly the viral DNA or RNA in such a way that it is not replicated which is termed as ''Gene Silencing'' thus the Virus cannot replicate and cannot infect new cells. This mechanism is even more effective than the one used by animals (antibodies). Just the plants have to recognize these signals. Plants have this mechanism naturally. You will be amazed to find that wild orchids and species are rarely infected with Viruses. It is because natural selection keeps weeding out plants that do not have such effective mechanisms. But by hybridization and selection for certain aesthetic characteristics man has selected and developed plants that lack or are insufficient in some ways in these mechanisms. But if you can make the plant recognise that it has been infected most plant will be able to silence the viral genes. There is a lot of research regarding what these signals are. Various signals like heat shocks, cold treatments, certain chemicals and even certain plant and viral RNAs are the triggers that can induce this reaction.