Current plant varieties resist Biotype 1 aphids. But crop sciences and plant pathologist Glen Hartman and research specialist Curt Hill said Tuesday that Biotype 2, which showed up in 2006, and Biotype 3, found recently in Indiana, both appear to have developed resistance genes of their own.
Hartman says it is in the genetic background of the minuscule green insect to find a way to overcome plant resistance.
Hartman said aphids are thought to have entered the United States from China in 2000, adding it is difficult to determine exactly how they entered.
Aphids have spread to more than 20 states, and can significantly reduce soybean yields if not caught early.