The build-up of viruses and other kinds of pathogens in perennial plants eventually drains the plants of their strength, and gardeners must replace them. Insects and other arthropods are the most common way viruses move from place to place. Traveling the world, people carrying propagative plant parts and seeds also help transport viruses. Recent advances have made testing plant material for viruses faster and more accurate. Tissue culture can be used to eliminate viruses from infected plants, so virus-free plants can be produced.
Many companies offer seeds and propagative parts that are certified virus-free.
It is important to inspect new transplants or seedlings for signs of viral infection. Infected plants often stand out from healthy plants because they are stunted, yellowed, or show a mosaic pattern on the leaves. But some of these symptoms may reflect problems unrelated to viruses. Any suspicious plants should be removed to avoid infection of nearby plants. Weeds can carry many common viruses, which is another good reason to weed regularly or to mulch.