Alfalfa mosaic virus symptoms can include bright yellowing along leaf veins, broad rings, and mosaic patterns. This virus is transmitted by several aphid species. Some varieties of tobacco are more susceptible than others. (Photo: Kenneth Seebold, UK)

Alfalfa mosaic virus symptoms on a burley leaf tip. (Photo: Kenneth Seebold, UK)

Symptoms of alfalfa mosaic virus often first show up in tobacco field border rows; this is referred to as an "edge effect" and is related to the aphid vector dispersal pattern. (Photo: William Nesmith, UK)