I nsect-t ransm itted viruses threaten agriculture

The vast movement of people and agricultural products between dis- tant geographical regions has cre- ated unprecedented opportunities for introducing plant viruses and the insects that carry them (vec- tors) to new areas. Outbreaks of new viruses may be favored in these agroecosystems by crop susceptibility, the presence of par- ticular weeds and certain agricul- tural practices. In some cases, conditions in these ecosystems may be ideal for the emergence of sltered plant viruses and new virus/vector relationships. This may result in the appearance of insect-transmitted plant viruses in