Loss in Corn Yield Associated with the Abundance of the Corn Leaf Aphid, Rhopalosiphum maidis, in Indiana1

Abstract

The corn leaf aphid is a common pest of corn in Indiana, causing occasional damage in a few widely scattered fields. In 1959, conditions favored the development of this insect and serious losses occurred in many corn fields in the northern two-thirds of the State. The area of heaviest infestation was a band three counties wide in the north central part of the State, from Warren and Fountain counties on the west to the Ohio line, and a single row of counties north and west along the Michigan line to Lake Michigan. The area of greatest losses followed a similar pattern. Losses in yield as high as 40% occurred in many fields. The data obtained under these conditions of widespread and heavy infestations supported previous observations that severe infestations result in barren plants. In addition, such infestations also increased the production of nubbins. In one field, data indicated that light infestations can also reduce the yields as much as 10% through decreased size and weight of ears. There was also evidence that commercial hybrid corn varies in degree of infestation and tolerance to loss by this insect. Data from the 12 areas of Indiana used for the Fall Corn Insect Survey indicated a high degree of correlation between loss of yield and per cent of plants infested. It was possible to estimate the amount of loss in individual fields from this relationship when the percentage of plants infested was known. The relationship of reduction in yield and infestation by the corn leaf aphid will probably vary from year to year as the interaction of control factors change, but it indicated the possibility of establishing a relationship of infestation and loss through the proper evaluation of environmental factors.