The common 'Tiger Lily' has the ability to host viruses without showing any symptoms whatsoever. It's always a good idea to plant them a good distance (100 feet) from your other commercial type lilies; especially your prized ones because they can catch certain viruses. And, when they do, they become distorted and weaker and eventually die. Once a single plant within a group gets a virus infection, it's just a matter of time until they all get it unless prompt action is taken to remove and destroy the infected plant material and bulb.
Ants that slave farm aphids and gardeners themselves are the major transporters of the viruses from plant to plant.
