Chlorotic dwarf (CD), the most important disease in the sweet potato-produc
ing regions of Argentina, is caused by the synergistic combination of two a
phid-transmitted potyviruses with a whitefly-transmitted crinivirus. Sweet
potato feathery mottle virus, sweet potato mild speckling virus, and a crin
ivirus (serologically related to sweet potato chlorotic stunt virus) were a
ssociated with CD. The synergistic combination of these three viruses repro
duced the disease.