Biocontrol introduction
Target pest: Costelytra giveni (Coleoptera: Scarabaeidae), New Zealand grass grub
Agent introduced: Pseudelaphroptera brevipilosa (Hymenoptera: Thynnidae)
Imported:
1965-73
Import source:
Argentina
Import notes:
Cameron et al. (1989) - Pseudelaphroptera brevipilosa was reared from field-collected melolonthine Scarabaeidae [i.e. in the same subfamily as C. giveni] or white-fringed weevils (Graphognathus leucoloma) in Argentina and 76,178 females or pairs were shipped to New Zealand between 1965 and 1973.
Released:
1965
Release details:
Cameron et al. (1989) - a total of 36,735 mated female P. brevipilosa were released at nine sites in the northern South Island (in the Marlborough and Nelson regions) and at five sites in the northern North Island. Release details by year were as follows: 1965 - 205 released in Marlborough; 1966 - 12,130 in Taupo, Marlborough, Nelson; 1967 - 9,339 in Nelson; 1968 - 1,682 in Nelson; 1970 - 717 in Nelson; 1971 - 7,621 in Waikato, Bay of Plenty, Nelson; 1972 - 4,876 in Auckland, Bay of Plenty, Nelson; 1973 - 165 in Auckland, Bay of Plenty. As a result of thynnine cocoons being obtained from white-fringed weevil (Graphognathus leucoloma) larvae, P. brevipilosa releases from 1970 were partly directed against G. leucoloma [having been primarily imported against C. giveni].
Establishment:
Cameron et al. (1989) - forty-five P. brevipilosa males emerged from C. giveni caged in the field, and thynnine cocoons were also obtained from white-fringed weevil (Graphognathus leucoloma) larvae. No P. brevipilosa were reared from field-collected larvae of either host, but male thynnines were recalled by attracting them to tethered females 13 days after release in the Marlborough region. No further recoveries were reported and the evidence indicates an early failure to establish.
General comments:
Taxonomic note (8 April 2025) - a species of scarab beetle was described as Rhizotrogus zealandicus by White in 1846 from two specimens collected in the Wellington region. In 1952 Given described the genus Costelytra with the New Zealand grass grub as the type species, naming it C. zealandica, considering it conspecific with White’s Rhizotrogus zealandicus. However, Coca-Abia & Romero-Samper (2016) found differences between Given’s description of C. zealandica (i.e. New Zealand grass grub) and White’s specimens, and renamed the New Zealand grass grab Costelytra giveni, reserving the name C. zealandica (syn R. zealandicus) for the species described by White, considered by Coca-Abia & Romero-Samper (2016) likely to be a shrubland or forest species from the Wellington region. [All information from Coca-Abia & Romero-Samper (2016).]
References
Cameron PJ, Hill RL, Bain J, Thomas WP (1989). A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424p.
Coca-Abia MM, Romero-Samper J (2016). Establishment of the identity of Costelytra zealandica (White 1846) (Coleoptera: Scarabeidae: Melolonthinae) a species commonly known as the New Zealand grass grub. New Zealand Entomologist 39(2): 129-146 https://doi.org/10.1080/00779962.2016.1230254
