n African Entomology - The spread of Sirex noctilio Fabricius (Hymenoptera : Siricidae) in South African pine plantations and the introduction and establishment of its biological control agents
|Article Title||The spread of Sirex noctilio Fabricius (Hymenoptera : Siricidae) in South African pine plantations and the introduction and establishment of its biological control agents|
|© Publisher:||Entomological Society of South Africa (ESSA)|
|Author||G.D. Tribe and J.J. Cillie|
|Publication Date||Mar 2004|
|Pages||9 - 17|
|Keyword(s)||Biological control, Deladenus siricidicola, Ibalia leucospoides, Megarhyssa nortoni, Pine plantations, Sirex noctilio and South Africa|
Within eight years of its discovery in the Cape Peninsula in 1994, the Eurasian woodwasp, Sirex noctilio, has spread up to 380 km along both the western and southern coasts of South Africa. A biological control programme was begun within the first year with the importation of the Kamona strain of the parasitic nematode, Deladenus siricidicola, which had originally been imported into Australia from Hungary. In 1995 and 1996 a total of 70 million nematodes were imported and inoculated into 296 S. noctilio-infested trees in a 90km arc around Cape Town. The parasitism rate increased from 22.6% in 1996, to 54% in 1997, and 96.1% in 1998. The early larval parasitoid, Ibalia leucospoides, was imported into South Africa in 1998 from Uruguay, where it had arrived with its S. noctilio host. A total of 456 parasitoids was released in plantations from Cape Town to Riversdale from 1998-2001. By 2002 it was confirmed to be established at Stellenbosch. Megarhyssa nortoni, a late larval parasitoid originally from North America, was imported from Australia into South Africa in 1998 and 38 mated females were released on the Gifberg overlooking Vanrhynsdorp a year later. No recoveries from this site have been made and it is unknown whether it has become established. Since 1994, the numbers of the European cerambycid, Arhopalus syriacus, had increased because they were able to breed in the lower trunk of trees killed by S. noctilio. Their numbers have since declined with those of S. noctilio following the introduction of the natural enemies. At no stage did the loss of trees exceed 3.2% of a Pinus compartment and effective biological control was achieved during this period within the southwestern Cape.
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