Plant viruses are widespread in nature, where they operate in intimate association with their hosts and
often with vectors. Most research on plant viruses to the present has focused on agricultural systems
(agronomic and horticultural) and viruses that are pathogenic. Consequently, there is a dearth of fundamental
information about plant virus dynamics in natural ecosystems and how they might differ from or
be influenced by virus interactions in managed systems. Key questions include under what conditions the
influence of virus on host fitness is negative, neutral, or positive and the extent to which this relationship
is influenced by ecosystem properties.