Biocontrol introduction
Target pest: Metopolophium dirhodum (Hemiptera: Aphididae), rose-grain aphid
Agent introduced: Aphidius rhopalosiphi (Hymenoptera: Braconidae)
Imported:
1985
Import source:
England and France
Import notes:
Cameron et al. (1989) - Aphidius rhopalosiphi was sourced from southern England and western France. Shipments of 250 and 1,000 M. dirhodum mummies were imported into quarantine at Lincoln, Canterbury, in April and June 1985, respectively. The parasitoid was reared through three generations in the laboratory in order to exclude hyperparasitoids and disease from the stock.
Released:
1985
Release details:
Cameron et al. (1989) - parasitised mummies were released between June 1985 and January 1987 at 20 sites in the South Island - Southland (8,000), Mid Canterbury (163,000), North Canterbury (7,000), Marlborough (3,000) - and at one site in the North Island - Manawatu (5,000).
Establishment:
Cameron et al. (1989) - in surveys during November and December 1986 A. rhopalosiphi was found at nearly half of all sites in all areas except Marlborough and Manawatu. In 1987, numerous A. rhopalosiphi were recovered in Southland, Otago, Canterbury, Marlborough and Manawatu.
Farrell & Stufkens (1990) - Aphidius rhopalosiphi spread rapidly, and by late-1988 was found throughout cereal-growing areas of the South Island and southern North Island.
Impacts on target:
Cameron et al. (1989) - Aphidius rhopalosiphi population density and rate of parasitism of M. dirhodum was evaluated in Canterbury in October-December 1986, showing populations and parasitism comparable to southern England and western France. This parasitoid appears to be a useful addition to the range of biotic regulatory agents acting against M. dirhodum.
Grundy (1990) - it is estimated that the annual benefits of the biocontrol of M. dirhodum by A. rhopalosiphi are between $300,000 and $5 million. Anecdotal evidence from Canterbury cropping farmers indicates that aphids are much less a problem since the introduction of A. rhopalosiphi.
Farrell & Stufkens (1990) - a study of the impact of A. rhopalosiphi on M. dirhodum in Canterbury barley crops during 1988 and 1989 showed a greater impact in spring barley, where nearly 100% parasitism was recorded at peak aphid numbers, than in winter barley, where approximately 50% parasitism was recorded at the same stage. The decline of peak aphid population levels since introduction of the parasitoid was much greater in spring barley, from about 100 aphids per tiller in 1984 to less than five aphids per tiller in the four seasons 1986-1989, and was reflected in the ten- to twenty-fold drop in suction trap catches of M. dirhodum, contrasting with the increase of A. rhopalosiphi catches, between 1984 (prior to its release) and 1987-1989. A 60-100% parasitism of M. dirhodum by A. rhopalosiphi on spring-sown barley and wheat in the North Island has also been recorded.
Cameron et al. (1993) - Aphidius rhopalosiphi is categorised as exerting “substantial” control (defined as “other control measures are only occasionally required”) over M. dirhodum.
Impacts on non-targets:
Farrell & Stufkens (1990) - in addition to M. dirhodum, hosts of A. rhopalosiphi in New Zealand were found to comprise Sitobion fragariae, Rhopalosiphum padi,, Rhopalosiphum maidis and Myzus persicae (all introduced pests).
Teulon et al. (2008) - it appears that the impact on non-target aphid species of aphid parasitoids introduced as biocontrol agents was not examined until the introduction of A. rhopalosiphi in 1985 when this parasitoid species was only tested on other introduced aphid species. [The host species tested and results are not given.] DNA sequencing of parasitoids attacking New Zealand native aphids, from collections made since 1998, mostly in the South Island, found a range of braconid and aphelinid species. While some species have yet to be fully characterised and may be New Zealand native parasitoids new to science and other species need to be verified using morphological characters, one Aphidius sp. attacking Aphis healyi is a putative introduced species.
Bulman et al. (2021) - to identify Aphidiinae parasitoids [the subfamily of family Braconidae to which Aphidius belongs] of native New Zealand aphids, native aphids were collected throughout the South Island between 2006 and 2018. Aphidiinae parasitism was rare; in total, parasitism was observed from eight native aphid species at 16 locations. All cases of parasitism were by phylogenetically related native Aphidiinae, 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 Aphidiinae was found.
References
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
Farrell JA, Stufkens MW (1990). The impact of Aphidius rhopalosiphi (Hymenoptera: Aphidiidae) on populations of the rose grain aphid (Metopolophium dirhodum) (Hemiptera: Aphididae) on cereals in Canterbury, New Zealand. Bulletin of Entomological Research 80: 377-38
Grundy TP (1990). A cost-benefit analysis of biological control of rose-grain aphid in New Zealand. Proceedings of the 43rd New Zealand Weed and Pest Control Conference, 163-165 https://journal.nzpps.org/index.php/pnzwpcc/issue/view/vol43
Teulon DAJ, Drayton GM, Scott IAW (2008). Exotic introductions of primary parasitoids of aphids in New Zealand: the good and the bad. In: Proceedings of the Third International Symposium on Biological Control of Arthropods (eds PG Mason, DR Gillespie & C Vincent), pp. 421–430. USDA, Forest Service, Morgantown, WV. https://www.cabi.org/ISC/FullTextPDF/2009/20093074320.pdf
