Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Update on Argentine stem weevil biological control.

Abstract

Between 1988 and 1990, three visits were made to South America to search for and collect the braconid Microctonus hyperodae, a parasitoid of the Argentine stem weevil (Listronotus bonariensis), a severe pest of pastures, particularly short rotation ryegrass (the curculionid Lolium multiflorum), in New Zealand. As a result, 100 000 parasitised curculionids were released at experimental sites in the northern North Island, northern South Island, and Otago/Southland. Since this initial release, detailed research was conducted into the spread and build-up of the parasitoid. In most places, especially in the north, the parasitoid had become established and built up to high levels of parasitism (80%) with unexpected rapidity, although its rate of spread was modest at around 3 km p.a. Preliminary results from both Canterbury and the northern North Island indicate that the pest potential of the curculionid populations has already been affected in the release areas. Irrespective of its singular impact, which may be variable in space and time, it is apparent that M. hyperodae will hereafter play a major role in the management of the pest.