Development of a pesticide exclusion technique for assessing the impact ofbiological control agents for Chrysanthemoides monilifera

Seven biological control agents have been released on the environmental wee d Chrysanthemoides monilifera in Australia and two are widely established o n infestations of C. monilifera subsp. rotundata in New South Wales. Five p esticides were screened for their impact on seed production of C. monilifer a and two on the survival of the agent Comostolopsis germana, a shoot tip-f eeding lepidopteran. The insecticides carbaryl, carbofuran, dimethoate , fl uvalinate and the fungicide benomyl had no significant effect on seed produ ction of C. monilifera when applied over a period of four months. Numbers o f C. germana larvae were readily suppressed after three months by applicati ons of fluvalinate or a mixture of carbaryl, carbofuran and dimethoate Shoo t growth was not affected by applications of carbaryl, dimethoate and benom yl. It is concluded that exclusion by pesticides of biological control agen ts is a valid method of measuring the impact of agents on C. monilifera.