A new virus disease, soybean dwarf, was first noticed on the Tsurunoko variety of soybean in southern areas of Hokkaido in about 1952. Since then it has been widely observed throughout Hokkaido, causing a considerable loss in soybean yields. Soybean plants infected with the virus show dwarfing (stunting), and downward curling, rugosity, and/or interveinal yellowing of the leaves.
The virus was transmitted by grafting and by the aphid Aulacorthum solani (Kaltenbach), but not by juice inoculation or through seeds. Three species of aphids, Aphis glycines Matsumura, Aphis craccivora Koch and Myzus persicae (Sulzer), and two species of leafhoppers, Scleroracus flavopictus Ishihara, and Psammotettix striatus (Linné) failed to transmit the virus. The virus was retained in the vector A. solani for 20 days after leaving the source plants.
It was found that red clovers and white clovers in the neighborhood of affected soybean fields were symptomless carriers of the virus.