Aphids appear on grains in the spring and live in small colonies at the base of the inflorescence or inside the sheath of the covering leaf. When the crops ripen and aphid numbers increase, the colonies are found on the green parts of the plant, the plant inflorescence, or as low down as the first node of the stem. In June, colonies consist of adult parthenogenetic wingless females, immatures and winged colonizing females. Migration of winged adults usually takes place during the morning. Peak populations are present when the grain is nearly mature, with numbers decreasing rapidly after harvest.
Colonies subsist on the crop residue or on native grasses for the remainder of the season.
In old-world areas, sexual forms appear the first part of October and are present until the first frosts, with the resulting overwintering eggs hatching the next spring. The first detection in the new world was in central Mexico in 1980. RWA moved north to the state of Coahuila by 1983, and was found for the first time in the U.S. near Muleshoe, TX, March 17, 1986. The aphid spread to AZ, ID, MT, SD, OR, UT, and WA in 1987, CA in 1988, and NV in 1989. That year, a suction trap captured 2 specimens at Williston, ND, but was not actually found in the field until later.