Viruses and virus-like agents have recurring impact on quality fruit production throughout the life of an orchard. They are graft-transmissible and are readily disseminated through the use of infected budwood. Since many of these agents do not have arthropod or nematode vectors, the most effective control strategy is to develop orchards with clean, virus-tested planting stock. The implementation of quarantine and certification programmes on a global scale is essential to safeguard apple production and minimize the risk of spreading disease by removing virus-infected plants from the supply chain. Procedures for virus testing and elimination are constantly being revised to incorporate the best and most appropriate technologies.