Population monitoring studies of lucerne aphids and their predators in the Waikato

Abstract

Populations of Therioaphis trifolii form maculata, Acyrthosiphon kondoi and A. pisum and their predators were monitored on lucerne in New Zealand in 1983-84. A. kondoi reached peak populations in early spring, while the other 2 aphid species peaked in late summer or autumn. The predators Micromus tasmaniae and Melanostoma fasciatum probably contributed more towards the control of T. trifolii than did other natural enemies. The activity of spiders and Nabis capsiformis was not well enough synchronized to contribute effectively towards the control of T. trifolii. The other 2 aphid species probably have a beneficial role in the maintenance of natural enemies that transfer to and control T. trifolii as infestation builds up.