The Biology and Main Causes of Changes in Numbers of the Rose Aphid, Macrosiphum Rosae (L.), On Cultivated Roses in South Australia.

Abstract

In South Australia, M. rosae is anholocyclic on Rosa, reproducing parthenogentically and viviparously all year round. It feeds mainly on the young leaves and developing flower-buds of hybrid tea roses. The fate of a colony of aphids on a single bud is a function of temperature, rainfall, predation, the time for which the bud remains favourable for the aphids, and the influence of crowding on alatiform production and on dispersal of apterae by walking or dropping off. The numbers of aphids on cultivated hybrid tea roses in a rose garden had three peaks in spring-summer which coincided with three flushes of growth of the rose. The first peak, in spring, was the highest; thereafter numbers of aphids were relatively low, mainly because of predation by three species of native predators, namely the hemerobiid Micromus tasmaniae, the syrphid Melangyna viridiceps and the ladybird Leis conformis. The study was a prelude to computer simulation of the population dynamics of the aphid which will be used to investigate the problem of the regulation of density in natural populations of aphids.