Minn. Much of the research is supported in part by the Minnesota Wheat Checkoff, administered by the Minnesota Wheat Research and Promotion Council. Infestations can be sporadic. There's no telling where you are going to get them. One field may be colonized, while the field next door may be clean. Some later-planted fields may still be vulnerable to aphids, but scout and treat fields only if warranted.
Aphid treatment is optimal when wheat is in the flag leaf stage.
Parasitic insects, rain, and a fungal disease that kills aphids will help reduce aphid populations as the growing season progresses. There are several species of aphids, including greenbug, English grain aphid, and bird cherry-oat aphids, which transmit barley yellow dwarf virus in small grains. This disease is causing some stunting and yellowing of wheat and barley this year. However, stem and leaf rust has been the most predominant disease in small grains thus far this growing season. Stem rust samples received this year at the U.S. Agriculture Department's Cereal Disease Lab in St. Paul, Minn., are twice as great as in recent years.