Activity of adult Heliothis armigera (Hb.) (Lepidoptera, Noctuidae) with reference to the flowering of sorghum and maize in Botswana

Abstract

Night-time observations on adults of Heliothis armigera (Hb.), and data from light-trap and hand net catches in irrigated and dryland crops, showed that both sexes flew and fed and females oviposited between 20.00 and 23.00 h. From then until 02.00 h both sexes were inactive, but. from 02.00 to 04.00 h the males flew above the crop in a ‘purposeful’ manner, while the females were stationary and releasing pheromone. During this period of high male and low female activity, copulation in cages, assembly of males to females in cages and copulating pairs on crop plants were all observed. Inseminated female H. armigera were collected in crops which were at a stage suitable for oviposition, while traps away from crops or near mature crops collected mainly virgin females. It is suggested that susceptible crops attract H. armigera adults and that, once within the crop, inseminated females are ‘trapped’ by suitable physiological cues from the plants. Identification of such cues could assist in the breeding of crop varieties resistant to H. armigera attack.