Within-plant distribution of the immatures ofHeliothis zea(Boddie) on cotton

A detailed study of the within-plant distribution of cotton bollworm (Heliothis zea (Boddie)), its eggs and larvae, was conducted in the field, and sampling schemes for them were developed. The average location of bollworm eggs was approximately one-third of the distance in nodes from the terminal, while older larvae were found lower on the plant than younger larvae. The sampling scheme for bollworm eggs relies on the finding that the mainstem leaves are the preferred oviposition site. Field observations indicate that early first instar larvae can be detected in squares by the presence of frass and the flaring of the bracts. These criteria are used in a suggested sampling scheme for first-through-third instar larvae.