A synopsis of the Sirex problem in radiata pine plantations in south-eastern Australia.  F. G. Neumann and G. Minko.  August 1980.  34 pp. (unpubl.)

SUMMARY

In south- eastern Australia, the European wood wasp Sirex noctilio, with its pathogenic fungal symbiont Amylostereum areolatum, is a serious tree-killing agent and a threat to approximately 425 500 ha of exotic Pinus radiata plantations. Some unthinned stands of intermediate age and valuable shelterbelts on farmland have been severely damaged in Tasmania and Victoria, whereas healthy and vigorous plantations have remained undamaged, suggesting that S. noctilio is essentially a secondary pest.

One-year life cycles are predominant, but three-month cycles and two or three-year cycles are also known. Peak emergence of adults and of attack on pine occur during mid-summer, when soil moisture levels, growth rates and tolerance of pine to pests and diseases are low.

In Tasmanian plantations, introduced ichneumonid and stephanid parasitoids, and the parasitic nematode Deladenus siricidicola, have been effective control agents, though some outbreaks have collapsed even without natural enemies. In some parts of Victoria, where droughts are frequent and summer temperatures are high, ecological balance between host and parasite populations may occur only after an unacceptably high level of tree mortality in stands of intermediate age that have remained unthinned due to unfavourable markets and unavailability of funds for sanitation felling. For such stands, a control strategy is being devised that will combine the effects of established biological control agents and minimum, selective non-commercial thinning, with the strategic placement of groups of trap trees, which have been predisposed to S. noctilio attack by injection with herbicide during spring.

Also published:

Neumann, F.G. and Minko, G. (1981)  The Sirex woodwasp in Australian radiata pine plantations.  Aust. For. 44 (1): 46-63.