Fecundity and Diurnal Oviposition Behaviour of Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae)

The fecundity and diurnal oviposition behaviour of Atherigona soccata was studied on CSH 5, a susceptible sorghum genotype, under greenhouse conditions. The fecundity of females deprived of 10-day-old sorghum seedlings was drastically reduced, and no fertile eggs were laid after 11 days of host deprivation. However, when the females were provided with host plants, egg production was prolonged, and fell considerably after the flies reached 22 days of age. There were three distinct peaks (6-7, 13-14 and 18-19 days of age) in egg-laying activity. Further studies with flies of three age groups (7, 13 and 19 days old) did not show significant differences in diurnal oviposition pattern with age. However, most eggs (60%) were laid between 08.00 and 12.00 h. It was evident from the present study that the prolonged egg-laying capacity of female A. soccata when provided with a susceptible host may partly account for the dramatic increase in damage as the crop season advances, since there would be a geometric increase in active females with every new generation of flies