Biocontrol introduction
Target pest: Caliroa cerasi (Hymenoptera: Tenthredinidae), cherryslug, pear slug
Agent introduced: Lathrolestes luteolator (Hymenoptera: Ichneumonidae)
Imported:
1923, 1929, 1972, 1973, 1974
Import source:
England (1923, 1929), France (1929, 1972, 1973, 1974), Austria (1972), Germany (1972, 1973)
Import notes:
Cameron et al. (1989) - in 1923, 850 C. cerasi cocoons in February, and 400 in September, were imported into New Zealand from England (and presumably collected in southern England). From January to April 1924, 26 female and two male L. luteolator emerged, and in November and December a further 29 females and six males emerged after diapause. Attempts to parasitise C. cerasi in the laboratory were unsuccessful with the January - April emerging wasps (and emerging parasitoids were eventually directly released in the field) and yielded 21 males but no females from the November - December emerging wasps (which were also released in the field after parasitising C. cerasi in the laboratory). In 1929, 6,524 C. cerasi cocoons from France and England were sent to New Zealand; some were cool-stored (the fate of these is not recorded), the remainder reared. By 22 February 1930, three female and three male L. luteolator had emerged; the females at least were released. In November 1972, 2,070 C. cerasi cocoons from Austria, France and Germany were sent to New Zealand; L. luteolator emerged from these cocoons and were reared on field-collected C. cerasi larvae, but the colony failed because many of the host larvae were killed by the protozoan Blastocrithidia caliroae. In October 1973, 4,750 C. cerasi cocoons from France and Germany arrived in New Zealand. Most were cool-stored until spring 1974, at which time 16 male and 14 female L. luteolator emerged. Another shipment of cocoons (6,300, from France) arrived in October 1974, and cool-stored until spring 1975, at which time 68 L. luteolator emerged and were released.
Released:
1924
Release details:
Cameron et al. (1989) - twenty-one L. luteolator plus an unknown number of parasitised hosts were released in 1924 at Nelson in the South Island. In 1929, three female (of which at least two were unmated) and possibly three male adults were also released at Nelson. In 1975, 47 females and 21 males were released in Auckland and 10 females and seven males at Thames; both sites in the North Island.
Establishment:
Cameron et al. (1989) - Lathrolestes luteolator was first recorded in Nelson in 1963, was commonly seen at one Nelson site in 1970 and in 1972 over 50% parasitism of C. cerasi larvae was recorded at Blenheim, 100 km from the original release site. It has not been recorded elsewhere; other than these records, nothing is known about the distribution of L. luteolator in New Zealand. Given that it appears this species established in Nelson after the release of less than 30 adults and an unknown number of parasitised host larvae, it is possible it could be established from the relatively small numbers released in Auckland and Thames in 1975; however, no attempt has been made to evaluate these releases.
Impacts on target:
Cameron et al. (1989) - in central Europe L. luteolator is a bivoltine species sometimes attacking a high proportion of larvae in both generations of C. cerasi. However, in Nelson, it only attacks the spring generation of C. cerasi (for unknown reasons - potential explanations are daylength differences or that the strain established in Nelson in the 1920s was intrinsically univoltine) and so is of less value as a biocontrol agent. However, it was found parasitising 90% of C. cerasi larvae collected in Nelson in December 1973; it may therefore be an effective early season parasitoid. By February the level had reduced to 5% as the L. luteolator population declined. Overall, L. luteolator appears to be ineffective because it only attacks the less damaging of the two pest generations.
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.
