Climate matching in the colonisation of biological control agents against Chrysanthemoides monilifera and Marrubium vulgare / Craig R. Clarke.

Abstract

Releases of classical biological control agents targeting weeds often fail to establish in the field. This thesis tested the importance of climate matching, predation, release technique, laboratory adaptation and inbreeding using two model systems; the bitou tip moth Comostolopsis germana, for the control of the weed Chrysanthemoides monilifera; and the plume moth Wheeleria spilodactylus for the control of horehound Marrubium vulgare. The hypothesis tested was that the moths failed to establish because they were poorly adapted to South Australia's Mediterranean climate. The bitou tip moth failed to establish primarily due to ant predation, but was also found to be poorly adapted to host plants suffering from moisture stress. A collection of imported French moths reared in the laboratory since 1992 were found to be suffering from inbreeding depression. Both Spanish and French moths imported in 1996 and 1997 performed well in the field, in contrast to predictions on climate matching on the basis of temperature and rainfall.