Biocontrol introduction
Target pest: Sirex noctilio (Hymenoptera: Siricidae), sirex wood wasp
Agent introduced: Beddingia siricidicola (Rhabditida: Beddingiidae) = Deladenus siricidicola
Import source:
Nuttall (1980) - Beddingia siricidicola was self-introduced to North Island of New Zealand. It was first discovered in New Zealand in 1962 [and designated as Deladenus sp. - see taxonomic note (27 February 2023) in 'General comments' section] and later found to be present in Europe, from where it must have come in sirex-infested timber. There are several strains of the nematode in Europe, two of which are established in New Zealand [see Zondag (1975) entry in 'Import notes' section].
Import notes:
Zondag (1969) - not deliberately imported into New Zealand. Infection of Sirex noctilio by this nematode was first discovered in adult females emerging from Pinus patula logs from Rotehu State Forest (Bay of Plenty, North Island) in 1962. The nematode was determined to be in the genus Deladenus. The taxonomic status of the nematode remains a problem; it is also possible that in New Zealand more than one species is involved. [It was later determined to be a single species and described as D. siricidicola, and subsequently Beddingia siricidicola - see taxonomic note (27 February 2023) in ‘General comments’ section.]
Zondag (1975) - at present two strains of B. siricidicola are known in New Zealand: a strain that sterilises its S. noctilio host, which is established in all pine forests in the North Island, and a non-sterilising strain. The presence of the non-sterilising strain was recognised in 1971 and it has been found only in a few Northland forests and one forest in the Coromandel. In these forests the sterilising strain is also present.
Released:
Self-introduced in the North Island (first detected 1962), 1967 (South Island)
Release details:
Zondag (1975) - Beddingia siricidicola is self-introduced in the North Island, where it is present in all pine forests. Since it could not be found in any South Island forests, it was decided in 1967 to introduce the sterilising strain [see Zondag (1975) in ‘Import notes’ section] there. It was released into: four forests in Nelson in 1967, 1970 and 1973; one forest in Westland in 1974; six forests in Canterbury 1967-69 and 1971-73; eight forests in Southland 1967-69 and 1971-73.
Zondag (1979) - South Island introductions, subsequent to those from 1967 to 1974 [see Zondag (1975) entry above] are being continued.
Establishment:
Zondag (1969) - Beddingia siricidicola [then Delandenus sp.] was first detected in New Zealand in 1962 in Bay of Plenty, North lsland. Surveys subsequent to 1963 have shown it is also present in most North Island pine forests. It had not been found in the South Island by 1967, when deliberate introductions were made.
Zondag (1975) - the outcome of the South Island releases were as follows. Nelson: after the 1967 releases in Rai-Whangamoa State Forest, B. siricidicola was recovered in small numbers from Motueka State Forest and Pigeon Valley in 1970, a natural spread of about 50 km. In subsequent years, natural spread resulted in establishment in other forests in the northern part of the region. In Golden Downs State Forest infection of over 90% was recorded in S. noctilio in the 1973-74 season; the nematode had been released there in 1973, but had already been recovered from a few S. noctilio in the 1971-72 and 1972-73 seasons. Infection rates of over 75% have also been recorded in other parts of Nelson. The nematode can be regarded as successfully established in the northern Nelson region. Westland: no recoveries. Canterbury: recovered from two of the six release forests, Ashley and Omihi State Forests. In Ashley, spread occurred throughout the forest but infection rates were low and checks have not been carried out since 1973. In Omihi, only small numbers of infected S. noctilio were found in the four years following the 1967 release, and none in subsequent years. Southland: recovered from five of the eight release forests. In a number of these, recovery took several years and infection rates are still low.
Zondag (1979) - the disappointing known establishments in Canterbury and Southland, compared to the highly successful establishment in Nelson [see Zondag (1975) entry above], are believed to be due to very low levels of S. noctilio activity in most of the Canterbury and Southland forests.
Impacts on target:
Zondag (1969) - Beddingia siricidicola [then Delandenus sp.] is considered to be a very useful biocontrol agent, since infection results in complete sterilisation of adult S. noctilio of both sexes, and a high percentage of infected emerging adults (up to 95%) has been encountered in several areas. Parasitism by the nematode has sometimes been found to be higher than that of the combined efforts of the biocontrol parasitoids Ibalia leucospoides and Rhyssa persuasoria persuasoria. However, both parasitoids can develop in an on nematode-infected S. noctilio larvae, making it difficult to apportion S. noctilio mortality between nematode and insect parasites. During the past 10 years the population of S. noctilio in forests in both islands has persisted at low to moderate levels, with occasional local heavy mortality to trees. One of the factors considered responsible for the low population level is the establishment of biocontrol agents, the most important of which appears to be Beddingia siricidicola.
Zondag (1975) - the non-sterilising strain of B. siricidicola [see Zondag (1975) in ‘Import notes’ section] is known from two regions in the northern North Island. Investigations into this strain will be continued, as it is likely it will spread to other localities in the future and could cause a setback to the biocontrol of S. noctilio.
Zondag (1979) - Beddingia siricidicola is regarded as the most important controlling agent of S. noctilio in the North Island.
General comments:
Taxonomic note (27 February 2023) - nematode parasitism of Sirex noctilio was discovered in New Zealand in 1962; the species found was determined to be in the genus Deladenus (Zondag 1969). Subsequently, the nematodes from New Zealand and various siricid wasp hosts from many European countries were described as two new species, Deladenus wilsoni and D. siricidicola by Bedding (1968). The species in New Zealand, which is also present in Europe, is D. siricidicola (Bedding 1972). Blinova and Korenchenko (1986, in Bedding 2009) assigned those species previously included in the genus Deladenus having both free-living and parasitic life cycles associated with extreme adult female dimorphism (which included D. siricidicola) to a new genus, Beddingia. Poinar et al. (2002) established a new family, Beddingiidae, with Beddingia as its only genus.
References
Bedding RA (1968). Deladenus wilsoni n. sp. and D. siricidicola n. sp. (Neotylenchidae), entomophagous-mycetophagous nematodes parasitic in siricid woodwasps. Nematologica 14(4): 515-525
Bedding RA (1972). Biology of Deladenus siricidicola (Neotylenchidae) an entomophagous-mycetophagous nematode parasitic in siricid woodwasps. Nematologica 18(4): 482-493
Bedding RA (2009). Controlling the pine-killing woodwasp, Sirex noctilio, with nematodes. In: Hajek AE, Glare TR, O’Callaghan M (eds) Use of microbes for control and eradication of invasive arthropods. Progress in Biological Control, vol 6. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-8560-4_12
Nuttall MJ (1980). Deladenus siricidicola Bedding (Nematoda: Neotylenchidae). Nematode parasite of sirex. New Zealand Forest Service, Forest and Timber Insects in New Zealand No. 48: 8pp.
Poinar Jr GO, Jackson TA, Bell NL, Wahid MB (2002). Elaeolenchus arthenonema n. g., n. sp. (Nematoda: Sphaerularioidea: Anandranematidae n. fam.) parasitic in the palm-pollinating weevil Elaeidobius kamerunicus Faust, with a phylogenetic synopsis of the Sphaerularioidea Lubbock, 1861. Systematic Parasitology 52: 219-225 https://doi.org/10.1023/A:1015741820235
Zondag R (1969). A nematode infection of Sirex noctilio (F.) in New Zealand. New Zealand Journal of Science, 12(4): 732-747 https://www.fabinet.up.ac.za/publication/pdfs/2805-zondag1969nzjsci.pdf
Zondag R (1975). Controlling Sirex with a nematode. Proceedings of the New Zealand Weed and Pest Control Conference 28: 196-199 https://journal.nzpps.org/index.php/pnzwpcc/article/view/9154/8986
Zondag R (1979). Control of Sirex noctilio F. with Deladenus siricidicola Bedding. Part II: Introductions and establishments in the South Island 1968-75. New Zealand Journal of Forest Science 9(1): 68-76 https://www.scionresearch.com/__data/assets/pdf_file/0009/59175/NZJFS911979ZONDAG68_76.pdf
