The Russian wheat aphid is different from these aphids, having a spindle shaped body, uniform lime green color, absence of prominent cornicles and a double or forked tail. The greenbug and Russian wheat aphid are considered to be the most injurious, because during feeding these aphids inject a toxic saliva into the plants, causing discoloration and tissue destruction. Feeding will also cause inward rolling of leaves and often a purplish discoloration. Greenbugs cause a yellowish or tan discoloration of leaf tissue. The English grain aphid begins population buildups on the leaves of small grains and later in the season moves to the heads of grain.
Plants can tolerate larger populations of English grain aphids than of greenbugs.
Corn leaf aphid populations can build up very rapidly on corn, especially on tassles. Infestations on corn are seldom economically important, except possibly in extremely late seeded crops or crops growing under drought stress. The corn leaf aphid can also be found on barley, where it can inflict economic loss. The bird cherry-oat aphid, like other grain aphids, spends almost its entire feeding period on various grains and grasses. In recent years this aphid has been quite prevalent in North Dakota small grain, but most years it is of minor economic significance.