Target pest: Eriosoma lanigerum (Hemiptera: Aphididae), woolly apple aphid
Agent introduced: Aphelinus mali (Hymenoptera: Aphelinidae)
USA (Washington State, Connecticut and Arkansas)
Cameron et al. (1989) - Aphelinus mali was introduced into New Zealand from three locations in the USA (Washington State, Connecticut and Arkansas) in early-1921. Care was taken to eliminate secondary parasitoids of A. mali.
Cameron et al. (1989) - initial releases failed with the exception of three males and two females; it was from these individuals the subsequent release and distribution programme was developed. The initial release programme concentrated on the Nelson, South Island district and 3,000 were released there in the 1921-22 season. In 1922-23, 30,000 were released throughout the country. In 1923-24, 90,000 were released.
Camerson et al. (1989) - by October 1922 E. lanigerum was established in the Nelson (South Island) and Hawke's Bay (North Island) regions, and was widespread throughout New Zealand by 1925.
Impacts on target:
Cameron et al. (1989) - had almost eliminated E. lanigerum from orchards by 1925. Reports between 1938 and 1942 indicated some resurgence of E. lanigerum had occurred in many districts; this was attributed to variable activity of predaceous insects, disruption from the application of insecticides and the removal of parasitoid-infested prunings from orchards. Now, outbreaks of E. lanigerum occasionally occur in orchards where pesticide use disrupts biocontrol, but in the absence of pesticides this aphid is rarely a serious pest of apples in New Zealand and is adequately controlled by A. mali.
Cameron et al. (1993) - Aphelinus mali is categorised as exerting â€śsubstantialâ€ť control (defined as â€śother control measures are only occasionally requiredâ€ť) over E. lanigerum.
Rogers et al. (2015) - in New Zealand E. lanigerum management currently relies entirely on biological control, predominantly by A. mali. This provides effective control in the absence of disruptive insecticides. A severe and damaging outbreak of E. lanigerum in Hawkes Bay in 2007-08 was primarily caused by application of the insecticide spinetoram, but other insecticides can contribute to the instability of this biocontrol system. Since 2008 apple growers have reduced their use of disruptive pesticides, especially spinetoram, thiacloprid and carbaryl. Although E. lanigerum populations took several seasons to stabilise, there has not been a widespread outbreak since this period.
Impacts on non-targets:
Bulman et al. (2021) - to identify parasitoids of native New Zealand aphids, native aphids were collected throughout the South Island between 2006 and 2018. Parasitism was rare; in total only observed from eight native aphid species at 16 locations. All cases of parasitism were by phylogenetically related native Aphidiinae [a subfamily of family Braconidae that use aphids as hosts], and it seems reasonable to conclude that this is the predominant parasitoid threat that these aphids experience. The total number of parasitoids located was low due to the rarity of the aphid hosts themselves, so the possibility of infrequent interactions between biocontrol agents and endemic aphids cannot be eliminated. However, over the 14-year collection period of this study, no examples of native aphid parasitism by introduced parasitoids was found.
Bulman S, Drayton GM, Cameron PJ, Teulon DAJ, Walker GP (2021). Endemic New Zealand aphids (Hemiptera: Aphididae) parasitised by native Aphidiinae (Hymenoptera: Braconidae), not biological control parasitoids. Austral Entomology 60(4): 713-721 https://doi.org/10.1111/aen.12564
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.
Cameron PJ, Hill RL, Bain J, Thomas WP (1993). Analysis of importations for biological control of insect pests and weeds in New Zealand. Biocontrol Science and Technology 3(4): 387-404
Rogers DJ, Lo PL and Walker JTS (2015). Vulnerability of pest management in New Zealand apples: pesticide toxicity to Aphelinus mali (Hymenoptera: Encyrtidae) New Zealand Plant Protection 68: 299-305
Tillyard RJ (1923). History of the introduction of beneficial insects into New Zealand. Proceedings of the Pan-Pacific Science Congress, Australia, 383-390.