Biocontrol introduction
Target pest: Dasineura pyri (Diptera: Cecidomyiidae), pear leafcurling midge
Agent introduced: Platygaster demades (Hymenoptera: Platygastridae)
Imported:
1925-26
Import source:
France (1925-26), England (1926)
Import notes:
Cameron et al. (1989) - in 1925 three consignments were sent from France (the second collected near Paris; the localities were unspecified for the other consignments) of material potentially containing D. pyri parasitoids. The first shipment was of Contarinia pyrivora (pear midge)-infested pear fruit; no parasitoids emerged. The second shipment consisted of D. pyri-infested leaves from which the parasitoids Platygaster demades (identified at the time as Platygaster sp.), Torymus chloromerus and Isostemma boscii had been reared. Forty-one female and 21 male P. demades emerged; some were released in the field and others into an insectary at Henderson, Auckland containing D. pyri. The third shipment was a small amount of pear material infested by ‘midges’. Five female and three male P. demades emerged and were released into the Henderson insectary. In 1926, five consignments of parasitised D. pyri were sent to New Zealand; one from England, three from France and one originating from both countries. Dasineura pyri emerged in greater (but unspecified) numbers from these importations than from the 1925 importations. It was reported that the 1926 material was used to ensure establishment of D. pyri so presumably much of it was released from late-1926 to early-1927.
Released:
1925
Release details:
Cameron et al. (1989) - fifteen female and six male P. demades from the second 1925 importation [see Cameron et al. (1989) entry in ‘Import notes’ section] were released into an orchard in Henderson, Auckland in the North Island. Releases from the 1926 importations were not documented, but it was reported this material was used to achieve establishment on a sufficiently large scale, so presumably much of it was released from late-1926 to early-1927. In spring 1926, three female and one male P. demades were released in an orchard in Stoke, Nelson in the South Island. In December 1927, midge-infested foliage was distributed to various growers.
Establishment:
Cameron et al. (1989) - in the autumn of 1927, P. demades was recovered in Henderson, Auckland orchards where they had been released earlier in the season, presumably as adults from the 1926 importations. It successfully overwintered in 1927 and in spring 1927 a decided increase in the parasitoids in the field was noted. Fifteen months after the spring 1926 release at Stoke, Nelson, the species was found to be present there, and was considered well established at Henderson and Stoke by the end of 1927. In the year following the December 1927 distribution of midge-infested foliage to various growers, the orchards which had received the material were surveyed. Recoveries were made in several orchards in Auckland but nowhere else, and levels of parasitism were low. It was recovered in Dasineura mali (apple leafcurling midge) in Palmerston North (Manawatu region, North Island) in 1954. Platygaster demades has now been established in New Zealand for half a century and has been reported from all apple- and pear-growing regions.
Impacts on target:
Cameron et al. (1989) - in the 1933-34 season up to 33% parasitism of D. pryi by P. demades was found at Nelson, and up to 83% at Henderson, Auckland, and it was considered the parasitoid was exercising a very useful degree of control over the pest. However, D. pyri populations continued to reach damaging levels in all areas, and evidence suggests that a lack of synchronisation between the life cycle of this parasitoid and this host precludes the possibility of highly effective control in New Zealand.
Cameron et al. (1993) - Platygaster demades is categorised as exerting “partial” control (defined as “additional control remains commonly necessary but…pest outbreaks occur less frequently”) over D. pyri.
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.
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
