Influence of natural enemies on theSirexwood wasp in herbicide-treated trap trees of radiata pine in north-eastern Victoria

Abstract

From 1979 to 1982 in north-eastern Victoria, interactions between the European tree-killing wood wasp Sirex noctilio, the parasitic nematode Deladenus siricidicola, and the parasitoids lbalia leucospoides and Megarhyssa nortoni nortoni were studied within the sapwood of Pinus radiata trap trees treated with 200Jo dicamba herbicide. The level of biological control over time in such trees was assessed.Populations of the nematode did not affect the activity or survival of the parasitoids, nor restrict the fungal food supply to immature S. noctilio. Of the three biological control agents, the nematode was the most effective, inducing almost lOOOJo sterility in adultS. noctilio females (and a similar infection level among males), whereas parasitoids altogether caused only a maximum of 340Jo mortality of immature S. noctilio, in the second generation of trap trees. Among the four species of parasitoid released since 1976 near Myrtleford (Rhyssa persuasoria and R. hoferi were also liberated), only/. leucospoides showed any promise as an agent capable of contributing to Sirex control.Thus, biological control of S. noctilio in north-eastern Victoria mainly depends on the suppression of the pest's reproductive capacity by the parasitic nematode D. siricidicola. In highly susceptible unthinned plantations of intermediate age, this can best be achieved by maintaining for a minimum of two years a system of strategically placed trap trees injected with herbicide, along with populations of D. siricidicola and /. leucospoides.

Release of parasitoids forSirex noctiliocontrol by transporting infested logs

“…Options for increasing the sirex density, and thus the parasitoid density, include installing a trap tree system (Neumann eta/. 1982, Neumann andMorey 1984) and placing unmated female sirex with glued wings on these trees (Coutts 1965, Dolezal 1967). Furthermore, a 'field insectary' could be developed to produce a specific group of parasitoids (e.g., R. hoferi, R. persuasoria, and S. cinctipes).…”

“…The nematode Deladenus siricidicola Bedding, which sterilizes female sirex, is the key biological control agent in Australia (Bedding andAkhurst 1974, Neumann andMorey 1984). Nematodes can reach > 900Jo infection in a sirex population within four years after introduction and lead to a collapse of a sirex outbreak (Taylor 1981, Neumann andMorey 1984).…”

“…Nematodes can reach > 900Jo infection in a sirex population within four years after introduction and lead to a collapse of a sirex outbreak (Taylor 1981, Neumann andMorey 1984).…”

Trapping Techniques for Siricids and their Parasitoids (Hymenoptera: Siricidae and Ibaliidae) in the Southeastern United States

“…is diglycolamine salt; 480 g/liter; Vanquish, Syngenta Crop Protection, Inc., Greensboro, NC) in a distilled water solution into a 6-to 7-cmdeep and 10-mm-diameter predrilled hole every 10 cm around the treeÕs circumference. Holes were Ϸ15 cm above ground level and drilled at a downward 45Њ angle (Neumann et al 1982, Neumann andMorey 1984). The number of drilled holes ranged from Þve to eight per tree and the absolute amount of the a.i.…”

The Ecology, Behavior, and Biological Control Potential of Hymenopteran Parasitoids of Woodwasps (Hymenoptera: Siricidae) in North America

“…After mating, the females drill a hole 70 mm deep in wood to lay eggs on siricids (Tribe and Cillié 2004). The developing larvae are ectoparasitic, and they feed on late instar and pupal stages of S. noctilio, and presumably do the same on their native hosts (Neumann and Morey 1984). Megarhyssa spp.…”