Biocontrol introduction
Target pest: Mayetiola destructor (Diptera: Cecidomyiidae), hessian fly
Agent introduced: Pediobius epigonus (Hymenoptera: Eulophidae)
Imported:
1894, 1894-95?
Import source:
England
Import notes:
Cameron et al. (1989) - some thousand M. destructor pupae with parasitoids were shipped from England in December 1893 and arrived in New Zealand on 10 February 1894. A further shipment, planned for 1894-95, may never have been sent. It is not certain what parasitoid species were imported; English sources considered that Platygaster hiemalis and Pediobius epigonus were the species present in 1894 shipment; however, results from shipments sent at the same time to USA suggest that it is likely the shipment to New Zealand contained other species, including at least some of those reared from M. destructor in New Zealand in 1987, which were (in addition to P. hiemalis) Pediobius acantha, Aprostocetus zosimus and Eupelmus messene.
Released:
1894
Release details:
Cameron et al. (1989) - in February 1894 parasitoids [the species were not recorded, but would have included Platygaster hiemalis and Pediobius epigonus, and probably other species - see Cameron et al. (1989) entry in ‘Import notes’ section above] were released near Masterton and perhaps Marton in the [southern] North Island, and Milburn and probably Milton in the [southern] South Island.
Establishment:
Cameron et al. (1989) - Pediobius epigonus is established in the South Island from the 1894 releases [see Cameron et al. (1989) entry in ‘Release details’ section above] but has not been recorded from the North Island. Subsequent to these releases unidentified parasitoids of M. destructor were detected in the South Island from Balfour (Southland), Timaru (South Canterbury) and Lincoln (Canterbury). Pediobius epigonus was reared from M. destructor pupae from Methven (Mid Canterbury) in 1944.
Impacts on target:
Cameron et al. (1989) - most New Zealand records of M. destructor parasitism do not distinguish between species of parasitoids and the evaluation of the parasitoid complex has been inadequate to allow assessment of their impact on pest populations. In 1892-93 at various sites, 0-25% of fly pupae were parasitised. In about 1919, parasitoids dominated over M. destructor collected from Balfour (Otago, South Island), but at Lincoln (Canterbury, South Island) only 2-5% of pupae produced parasitoids. In the 1930s, a slight increase in parasitism was found as the season progressed, but during December and January it was not much more than 1%. Heavily parasitised M. destructor pupae were collected at Methven (Mid Canterbury) in January 1944. In 1987, 50% of M. destructor pupae from barley near Geraldine (South Canterbury) were parasitised (Platygaster hiemalis 38%, Pediobius acantha 6%, Aprostrocetus zosimus 6%), while 40% of pupae from wheat at Lincoln were parasitised (all by Eupelmus messene). Whatever benefits accrued from the parasitoid introduction would have been greatest until the 1940s when modern cultural controls became more effective. Overall, the introduction programme probably more than covered its costs. Introduced parasitoid species supplement control in situations, districts or on varieties that are more prone to attack.
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.
