Estimates of the Numbers of Heliothis Larvae Per Acre in Cotton and Their Relation to the Fruiting Cycle and Yield of the Host

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Abstract
Populations of Heliothis larvae composed of the bollworm, H . zea (Boddie), and the tobacco budworm, H . virescens (F.), were studied in small field plots undergoing treatment with various insecticides. The occurrence of larval populations broadly paralleled that of the flowering cycle of the host. Greatest numbers of the insects were present during the period when the plants had the greatest numbers of flowers. As the cotton approached maturity and bolls began to open and terminals and squares to abort, the larval population declined drastically. There appeared to be little relationship between the numbers of eggs deposited in the cotton fields and the subsequent numbers of larvae that survived. It was estimated from the results of this study that an average of 2000 to 2500 larvae (or approximately 1.5 to 2.0 per 10 ft of row) per acre are required to cause significant yield losses to cotton.