The present status of Anaphes nitens (Hymenoptera: Mymaridae), an egg parasitoid of the Eucalyptus snout beetle Gonipterus scutellatus, in the Western Cape Province of South Africa

Abstract

The egg parasitoid Anaphes nitens (Girault) was successfully introduced into South Africa in 1926 to control the Eucalyptus snout beetle, Gonipterus scutellatus Gyllenhal. However, outbreaks of the beetle on the Highveld in the 1980s questioned the efficacy of the parasitoid as a biological control agent and a programme was instituted to determine its present status. This study represents the Western Cape programme where 20 host egg-capsules were collected at fortnightly intervals for five years from three localities and the percentage parasitism was recorded. The mean parasitism rate varied between Cape Town (76%), George (82%), and Grabouw (89%). The highest parasitism occurred in spring (October) at Cape Town (96%) and (September) Grabouw (92%); and in autumn (May) at George (78%), coinciding with that of maximum host egg production, which in turn was dependent on the availability of fresh foliage. More host eggs were present in Cape Town (42%) than at either George (30%) or Grabouw (28%). Parasitism occurred consistently throughout the year at George which experiences all year rainfall, but the winter rainfall Cape Town and Grabouw localities experienced distinct peaks in parasitism in spring. Biological control of G. scutellatus remains effective in the Western Cape, from where A. nitens could be procured for release in Highveld regions in spring.

Key Words: Gonipterus scutellatus, Anaphes nitens, Eucalyptus snout beetle, biological control

Southern African Forestry Journal No.203 2005: 49-54