Flight Activity of the Corn Leaf Aphid in Wisconsin as Determined by Yellow Pan Trap Collections1

Abstract

Yellow-pan traps were used to determine the flight activity of the corn leaf aphid, Rhopalosiphum maidis (Fitch), in Wisconsin. The seasonal activity consisted of irregular fluctuations in sizes of collections from the first appearance of the species in the traps until late July to early August, when numbers increased greatly. Collections then decreased until late September to early October, when activity increased once again. By late October or mid-November, R. maidis was no longer present in the traps. This activity pattern was distinct from the resultant total pattern of all other aphids in the collections, which showed greatest activity in late May to early June. Observations in the field at Madison, Wis., indicated that percentages of alatae on corn were highest approximately 2 week before the first large alatae collections in yellow pan traps. The aphid colonies on corn tended to be largest approximately 10 days preceding large alatae collections in the traps.