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Biocontrol introduction

Target pest: Sirex noctilio (Hymenoptera: Siricidae), sirex wood wasp

Agent introduced: Rhyssa persuasoria persuasoria (Hymenoptera: Ichneumonidae)


1928-29, 1931, 1950, 1964

Import source:

Wales and England (1928-29, 1931, 1950); California, USA (1964)

Import notes:

Cameron et al. (1989) - larvae of R. p. persuasoria were collected from Wales and the south of England and sent to the Cawthron Institute in Nelson. Larvae were shipped under cool storage but some pupated and a number of these developed into adults during the voyage. From December 1928 to May 1929, 814 larvae, 40 pupae and 72 adults were received alive. Larvae and pupae were reared and adults emerged January - May 1929 and, from larvae which had carried over the winter, September 1929 - January 1930. In March, April and August 1931, 4,569 larvae, 1,166 pupae and one adult were received alive. Almost 15% of the 7,830 individuals dispatched from the UK died in transit, two-thirds of the emerging adults were male and many of the females emerged with damaged ovipositors, restricting the number of females that could be released. Some females from the 1931 consignments were used for laboratory rearing and by early-1937 four New Zealand generations had been reared, allowing some more small releases. In April 1950, an unexpected consignment of 472 R. p. persuasoria was received with a shipment of Ibalia leucospoides leucospoides [also introduced against S. noctilio]; as R. p. persuasoria was already established, these individuals were neither reared nor released. In 1964 two consignments of 'Rhyssa' spp., a total of 16 males and eight females, were received from California. These were later identified as a mixture of male R. persuasoria persuasoria, male and female R. alaskensis and, most numerous, male and female Pseudorhyssa maculicoxis. No oviposition was seen in the insectary and no progeny emerged.



Release details:

Cameron et al. (1989) - only 179 females were released from the imported material, and further small liberations were made from the reared material [see Cameron et al. (1989) entry in ‘Import notes’ section] at Rotorua (Bay of Plenty, North Island) and ‘in other districts’ such as Hanmer and Nelson in the South Island. However, the total number of females released between 1929 and 1936 was less than 200. Annually, from 1943 to 1950, the Cawthron Institute redistributed adults from forests where R. p. persuasoria was established, to a total of 16 South Island and five North Island locations. In 1950, there was some distribution of R. p. persuasoria, either as adults or larvae in logs infested with S. noctilio, by the Forest Research Institute into four exotic pine forests close to Rotorua (Bay of Plenty, North Island).


Cameron et al. (1989) - Rhyssa persuasoria persuasoria did not initially spread rapidly and only 11 records of establishment had been made by 1950. The first recoveries were made in the 1936-37 season from Moutere (Nelson) and Hanmer in the South Island. By 1950, establishment was known in the North Island at Riverhead (north of Auckland), Matahina and Rotorua (Bay of Plenty), Atiamuri (Waikato) and Taupo, and, in addition to the previous South Island records, at Balmoral, Darfield and Eyrewell (Canterbury), and Dumgree (near Blenheim). By 1959, R. p. persuasoria had spread to most exotic forests and by 1966 was established in all forests.

Impacts on target:

Cameron et al. (1989) - the presence of successfully introduced parasitoids [including R. p. persuasoria], together with the accidentally introduced nematode Deladenus siricidicola [subsequently reclassified as Beddingia siricidicola] and good forest management has been effective in keeping losses caused by S. noctilio at a low level. The combined effect of the introduced parasitoids may kill over 70% of S. noctilio larvae in a particular forest.

Cameron et al. (1993) - Rhyssa persuasoria persuasoria, in conjunction with Ibalia leucospoides leucospoides, Ibalia leucospoides ensiger and Megarhyssa nortoni nortoni [see the I. l. leucospoides, I. l. ensiger and M. n. nortoni introduction entries], is categorised as exerting “partial” control (defined as “additional control remains commonly necessary but…pest outbreaks occur less frequently”) over Sirex noctilio.


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