Argentine stem weevil (Listronotus bonariensis) survival in the central North Island

Abstract

Argentine stem weevil (Listronotus bonariensis (Kuschel)) populations in the central North Island were similar to Waikato populations and consisted of 2 complete generations per year, with negligible flight activity. There was a small spring and a larger summer generation. Populations had a higher overwintering survival, similar to that recorded in Canterbury. Overwintering survival was similar on several different ryegrass cultivars and over a wide range of host plant Acremonium endophyte infections. At the population densities often encountered on recently sown pastures in the Volcanic plateau, population survival (egg to adult) was not influenced by the proportion of ryegrass plants infected with Acremonium endophyte. The presence of endophyte deters adult weevils from ovipositing on infected ryegrasses but the presence of alternative hosts allows the population to develop. Population survival (egg to adult) was not associated with the ryegrass cultivar but was related to the initial egg density.

Keywords:

• Coleoptera
• Curculionidae
• Listronotus bonariensis
• population biology
• survival
• Acremonium endophyte
• Volcanic plateau