Contact, Seed and Soil Transmitted Plant Viruses

Plant viruses that spread without an insect vector: by contact and handling, through infected cuttings, tubers or other propagation material and seed, or through soil-dwelling nematodes. A virus belongs here when its cited article describes spread by mechanical contact, contaminated hands, tools and machinery, infected planting material or seed, or by nematodes in the soil, rather than by aphids, thrips, leafhoppers or other insects. Several of these viruses are very stable and can survive on tools, in plant debris and on seed, so a single infected plant or a handful of dirty tools can seed an outbreak in a nursery or field. Management relies on virus-free planting material, clean seed, hygiene for hands, tools and equipment, removal of infected plants, rotation or fallow where soil nematodes carry the virus, and resistant varieties where they exist. This heading gathers them so a visitor can compare their hosts and routes of spread.