Target pest: Gonipterus platensis (Coleoptera: Curculionidae), gum tree weevil
Agent introduced: Anaphes nitens (Hymenoptera: Mymaridae) = Anaphoidea nitens, Patasson nitens
Cameron et al. (1989) - a consignment of G. platensis [then considered to be G. scutellatus - see Mapondera et al. (2012) entry in the 'General comments' section] egg cases was received from Australia in October 1927. The 190 A. nitens which emerged in October and November were used to infest G. platensis eggs in an insectary, from which many adult parasitoids emerged. Most were released; the remainder kept to maintain the laboratory colony. However, this colony failed and in the 1929-30 season three further consignments of parasitised G. platensis eggs were imported from Australia (one consignment, however, was believed to parasitised by chalcid wasps only, although there is no record of any emerging), from which three generations of A. nitens were reared for releases.
Cameron et al. (1989) - 1927-28 releases from the 1927 importation were made at Henderson (Auckland), Mangaiti (Bay of Plenty), Orini (Waikato), 'Waitapu' (believed to be Waiotapu, Waikato), Waipukurau (Hawke's Bay), Bulls, Marton and Wellington in the North Island and Blenheim, Motueka and Darfield (Mid Canterbury) in the South Island. From the 1929-30 importations 486 adults were released in Nelson and parasitised egg cases were sent to Takaka (Nelson), Ashburton and Darfield in the South Island and Waipukurau in the North Island in the 1929-30 season. In the 1930-31 season it was redistributed (material reared from a small number of egg capsules obtained from Auckland) to Taranaki, Hawke's Bay and Auckland Provinces in the North Island and Nelson in the South Island. It is possible further releases were made in the South Island in the 1930-31 season, but this is unclear from the records. In the 1935-36 season releases were made at Hanmer Springs (Mid Canterbury) and Nelson.
Cameron et al. (1989) - in January 1930 it was known to have established in Auckland and Cambridge (Waikato) from the 1927-28 releases. In 1936 it was reported to be established in all the important districts of the North Island and in the Nelson Province and possibly in more southern areas of the South Island. (The difficulty of establishing it in the south was thought related to the single generation life cycle of the host in cooler districts.) Now occurs throughout New Zealand.
Impacts on target:
Cameron et al. (1989) - so rapid was the impact of A. nitens that only two years after its release there was a noticeable absence of G. platensis in Auckland and a marked improvement of the condition of its host trees there. By 1936 it was reported that weevil numbers were diminishing rapidly wherever the parasitoid had established. The rate of parasitism was high, e.g. it was reported in 1938 that 70-80% of weevil eggs in Auckland were found to be parasitised. A general low incidence of G. platensis attack has continued to the present. Considered an excellent example of biological control; A. nitens rapidly reduced host numbers and maintains them at a low level.
Mapondera et al. (2012) - the gum tree weevil, generally referred to as Gonipterus scutellatus Gyllenhal, 1833 is a significant pest of Eucalyptus species in Africa, America, Europe, New Zealand and Western Australia. [It is recorded in Cameron et al. (1989) as G. scutellatus.] Recent taxonomic study has indicated G. scutellatus to comprise a complex of cryptic species, obscuring the identity of the various pest populations of the weevil in the world. The pest species in New Zealand, America and western Europe was found to be G. platensis.
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.
Mapondera TS, Burgess T, Matsuki M, Oberprieler RG (2012). Identification and molecular phylogenetics of the cryptic species of the Gonipterus scutellatus complex (Coleoptera: Curculionidae: Gonipterini). Australian Journal of Entomology 51: 175-188