Estimating the Abundance of Corn Ear worm Eggs1

Abstract

The moths of the corn ear worm, Heliothis zea (Boddie), prefer to oviposit on fresh corn silk. A method is being sought, for use by field men, by which potentially heavily infested plantings can be located early enough for the successful application of insecticides. Two seasons' studies of the adaptation of black light traps to this use were unsuccessful. Wide variations existed between counts of eggs on corn silks made in the field and numbers actually present. A method was devised for removing eggs from silk for rapid counting under a low-power microscope. Silks were clipped from ears, brought to the laboratory and washed in clear gasoline in a 500 ml. flask. They were removed with a bristle- tipped stirring rod, the gasoline was floated and decanted off with 70% ethyl alcohol and the eggs, in the alcohol, were poured out into a watch glass.