An improved technique for early detection and control of sirex wasp in radiata pine plantations.  F. G. Neumann, J. A. Harris, F. Y. Kassaby and G. Minko.  July 1982.  17 pp. (unpubl.)

SUMMARY

Basal stem injection of Dicamba^† herbicide (20% 3,6-dichloro-2 methoxybenzoic acid) into the outer sapwood was tested as a technique for predisposing conveniently placed groups of Pinus radiata D.Don (radiata pine) trees to attack by the European tree-killing woodwasp Sirex noctilio Fabricius (Hymenoptera : Siricidae). A total of 14 336 trees was studied over a two-year in 32 plots of 448 trees, with 16 plots in each of an initially 8-year-old and a 15-year-old, unthinned plantation. Forty adjacent trees in each plot received one of four treatments, which were: injection of Dicamba during spring and summer, injection of deionised water during spring, and untreated controls; each treatment was replicated four times. The population level of S. noctilio in each plot was estimated from symptoms of the pest in the remaining 408 untreated trees.

Sirex noctilio was attracted almost exclusively to the Dicamba-treated trees, and these provided suitable breeding habitats for the pest and its introduced natural enemies (both wasp parasitoids and nematode parasites). Spring-injected trees of 10-19.9 cm diameter at breast height over bark, and aged about 15 years when treated, were most susceptible to attack. Infested treated trees contained an average of 275 wasps irrespective of tree age. Dicamba-injections did not induce major attacks on any nearby untreated trees.

The practical importance of these findings is that S. noctilio can now be readily detected, its populations periodically monitored, and control improved in plantations, by attracting the pest, and its lethal wasp parasitoids, to strategically placed and widely distributed groups of Dicamba-treated ‘trap’ trees. After felling, these trees can be inoculated during autumn with large numbers of Deladenus siricidicola Bedding (Neotylenchidae), a nematode parasite that infects S. noctilio larvae and ultimately sterilises adult females within the wood. When these infected sterile females emerge, they are expected to cause rapid and widespread dispersal of the nematodes, and introduce them, during oviposition drilling activity, into new ‘trap’ trees, in which another generation of Sirex females is expected to be sterilised, does hastening the decline of the pest.

^†Registered Trade Name. Use of trade names is for the information and convenience of the reader. Such use does not constitute official endorsement or approval by the Forests Commission Victoria of any product to the exclusion of others that may be equally suitable.

Also published:

Neumann, F.G., Harris, J.A., Kassaby, F.Y. and Minko, G. (1983)  An improved technique for early detection and control of sirex wasp in radiata pine plantations.  Aust. For. 45 (2): 117-24.