Movement of Aphis craccivora (Koch) and Melanaphis sacchari (Zehntner) between Plants Provides Further Evidence on Prevalence of Apterous Dispersal among Aphids

Abstract

A greenhouse study was conducted in the Botswana College of Agricultures’ greenhouse to determine the possible movement of two aphid species Aphis craccivora) (Koch), and Melanaphis sacchari (Zehntner), on cowpea and sorghum respectively. The aphid colonies of each species used were obtained from a greenhouse culture reared from progeny of single virginoparous apterous females. The plants were arranged such that one plant (the source plant) was put in the centre surrounded by four other plants (catch plants) so that the edges of the pots touched but without contact between the plants. In both experiments, each of the four groups of plants was kept on permanently moist irrigation matting in the greenhouse. The results showed that dispersal from initially colonized source plants occurred when plants appeared to be growing normally and when crowding was unlikely to be the cause. In both experiments this dispersal occurred when the population on the source plant exceeded about 10 adults and their offspring per plant. The implications of this behaviour are discussed, and it is argued that apterous dispersal may be common in aphids, allowing maximum utilization of the environment than would be likely by alate dispersal alone.