Investigations on the Cotton Bollworm, Heliothis armigera, Hübn. (obsoleta, Fabr.)

Abstract

Methods for the quantitative survey of the incidence of Heliothis armigera have been in continuous operation in the Barberton area of the Eastern Transvaal from 1929 to the present; since 1933 the Survey was operated similarly in Swaziland and Northern Natal.It was accepted early that the bollworm situation in cotton, which primarily it was desired to ameliorate, depends largely upon the influences exerted by other food-crops of the insect grown prior to and in association with cotton, and the investigations were instituted with a view to acquiring the fullest information on the incidence, habits and reactions of H. armigera with respect to the chain of cultivated and natural food-plant situations existing under differing climatic conditions in the course of the year.The present paper is the first of a series communicating the results of investigations which proceed in various directions from information supplied by the Cotton Pest Survey centred upon Barberton. The paper deals with the annual course of bollworm incidence as indicated, in the first instance, by egg counts taken twice-weekly, year by year, in examples of all food-plant situations according to methods of sampling and calculation devised here.