Aspects of Management of Subterranean Termites in Queensland

i ABSTRACT I investigated aspects of the management of subterranean termites in the field by evaluating the protective values of preservative treated softwoods and evaluating the potential of softwoods conditioned by decay fungi or heat to produce termite monitoring and aggregating devices. As part of the investigation, it was necessary to: · develop assay techniques suitable for research into the natural resistance of timbers, the efficacy of wood preservatives and termite biology and foraging behaviour; and quantify variation in termite responses to untreated softwoods in various situations in the field using these techniques. Field bioassays were conducted with two Australian Coptotermes species to determine protection of pine sapwood afforded by borate compounds (Chapter 2). Coptotermes lacteus (Froggatt) was examined in winter and C. acinaciformis (Froggatt) in winter, spring and summer at two localities in Queensland. Hoop-(Araucaria cunninghamii Ait ex D. Don) and slash-pine (Pinus elliottii Engelm.)-sapwood blocks were placed in plastic containers and attached to termite mounds or infested trees. Termite response was determined by mass losses over five weeks and modelled. Coptotermes lacteus was relatively benign in winter and for 1.0 and 2.5% mass losses of hoop-pine sapwood, borate retentions of 0.20 and 0.06% mass/mass (m/m) boric acid equivalent (BAE), respectively, were derived. With C. acinaciformis, for 1.0 and 5.0% mass losses of hoop-pine sapwood, borate retentions ranged from 0.49 and 0.25% BAE, respectively, in winter to 0.76 and 0.47% BAE, respectively, in late summer. For 1.0 and 5.0% mass losses of slash-pine sapwood in summer, borate retentions of 0.58 and 0.14% BAE, respectively, were derived for C. acinaciformis. These results support conclusions from earlier laboratory studies conducted elsewhere. Prevention of damage by field populations of termites was not achieved. Marked intercolony variation in response to borate compounds was demonstrated, highlighting the usefulness of this rapid technique. The need for long-term field exposure trials to calibrate the lunch-box technique and to facilitate technology transfer to industry, is indicated. For comparison, termite response to white cypress (Callitris glaucophylla Thompson and Johnson), a naturally termite resistant timber, is also reported. A field bioassay was conducted to evaluate responses of C. acinaciformis to untreated southern-yellow-pine (Pinus spp.), hoop-pine and slash-pine blocks (Chapter 3). Sapwood blocks were placed in plastic containers and attached to trees infested with the termites during summer. Containers with a test block of each of the timber species were prepared. These and other containers were exposed to termites for 10 weeks. Termite feeding response (voracity) was assessed for all blocks by determining the mass of wood consumed. Termite voracity differed among trees. Variation in termite responses to individual hoop-pine feeder-blocks within a container was appreciable and consistent between containers. Variation in termite responses to the test blocks was appreciable, with hoop pine being significantly more susceptible to termite attack than either slash pine or southern yellow pine. Southern yellow pine is a generic name for five species of pine which are difficult to separate reliably. Therefore, caution should be exercised when using southern yellow pine to ensure that samples are at least from the same species of pine and preferably from the same length of timber. The sensitivity of both the bioassay and the statistical tests was demonstrated. Of particular interest was the similar level of termite response to the test timbers in the two sections of the experiment. The usefulness of feeder-blocks to initiate reliable attack rather than to promote sustained attack, is worth further attention. Sapwood stakes of Australian-grown hoop pine, slash pine, radiata pine and North American-grown southern yellow pine were exposed to subterranean termite attack in an in-ground bioassay (Chapter 4). Stakes in bait containers and bare stakes were attacked by C. acinaciformis and Schedorhinotermes intermedius (Brauer). Susceptibility of these timbers was evaluated with regard to potential for termite monitoring and aggregation. Variation between timbers and difference between termite species are described. The relevance of these data to suppressing foraging populations of subterranean termites, in Australia, using insect growth regulators, is discussed. Four field bioassays were conducted using two species of Australian subterranean termites, C acinaciformis and C. lacteus (Chapter 5). Hoop-pine blocks decayed using 14 fungi for four weeks and for 10 weeks were subsequently conditioned using dry heating, freezing or moist heating, and then exposed to termites. Blocks decayed by Gloeophyllum abietinum [Persoon: Fries] Murrill, Trametes lilacino-gilva (Berkeley) Wright & Deschamps, Schizophyllum commune Fries and Rigidoporus undatus (Persoon) Donk and subsequently oven dried, were attacked the most. Oven drying generally enhanced termite feeding responses in these two field bioassays. In a third bioassay, blocks of five softwood timber species conditioned with two high temperature regimes were exposed to C. acinaciformis. Slash pine was attacked the least. Mean mass losses for hoop pine, Caribbean pine (Pinus caribaea Morelet), radiata pine and the interspecific F1 hybrid between Caribbean and slash pine were not significantly different. For C. lacteus, slash and hoop-pine blocks were attacked the least while radiata pine was attacked the most. Additional heating at 105°C increased the susceptibility of most timber species. Relationships between heating duration and the consumption of hoop-pine-sapwood blocks were determined using results from a fourth bioassay. Heating the timber increased feeding responses for both termite species. The selective and rapid response of the termites highlights the usefulness of this field technique for multiple-choice bioassays. The cyclodiene termiticides were withdrawn from use, in Australia, as from 30 June 1995. Implications for the management of subterranean termites in Queensland are discussed. Community perceptions of the use of chemical pesticides and cost do not favour the widespread use of preservative treated timber in buildings. An integrated pest management approach to termite control is the likely direction for the future in Australia. A range of building techniques, regular inspections, and attention to factors that predispose existing buildings to termite attack can reduce the risk of damage from termites, but do not eliminate that risk. There will be an increased need for reliable preventative and remedial treatments involving bait technology. Much more work is needed on termite biology, foraging behaviour and bait toxicants before a baiting system can be confidently commercialised in Australia. Directions for research in Queensland are discussed.