Populations can increase rapidly because they become reproductive 11 days after birth, and they give birth to live young. Corn leaf aphids and molted skins. Assessing the potential for aphid damage involves both the determination of how dense the aphid populations are on individual plants and how prevalent the infested plants are in the field. Most damage from the aphids occurs just before and during pollination, and scouting is critical. You cannot treat aphids while they are protected in the whorl, even though they cause losses.
Light infestations can develop into moderate or severe infestations within a week or two.
Repeated scouting is needed as tassels emerge and shortly thereafter. The decision to treat or not depends on considerable subjective assessment about the intensity of aphid infestations. Within the same field, you can have plants infested with different-sized populations of aphids. Use the information in Table 1 to help you plan treatment strategies. The data were generated from research first published in 1973 and have been refined in succeeding years.