There are more than 40 species of aphids in the Soybean field. The frequency of 18 species were aboue 0.1 percent. The Soybean aphid and peanaphid are vectors of SMV which peaked in the middle of July. Spinach aphid, has three peak stages include the end of june, middle of July and end of July. Diseaced plants appearred largely after 20th july. Plants infected primarily by SMV were the virus source transmitted by aphid.
Seedlings of seed-borne SMV and plants infected early by aphids carrying SMV decreased yield seriously and affected greatly percentage of seed-borne SMV.
Yield of aplant which appearred diseased after 9th July (R₂ period) were much higher than before. Percentage of seed-borne SMV of plants which appearred diseased before 16th July was hiyher clearly than Cater. The earlier disease developement, the more percentage of seed-borne SMV. It reached to the highest about 26 per cent at the end of June and early in July.