Although termites serve the ecologically important function of converting dead trees into organic matter, they annually cause damage worth billions of dollars to human structures such as houses, power poles and bridges throughout the world. This led to the development of various chemical and physical measures that primarily aimed at preventing the termites from causing damage to wooden structures. While the adverse effects of the chemical methods on the environment and human health has made them widely unacceptable, physical methods are costly and difficult to implement. There is a specific need to develop an environment friendly, cost effective, easily applicable and durable alternative barrier that would effectively protect a wide range of wooden structures. This study aims at designing and developing an eco-friendly, robust and easy to apply barrier material to protect wooden structures. Ether polyurethane (EPU) was chosen as the base material considering its toughness, resilience, hydrolytic stability due to the presence of ether group and easy applicability on large, irregular surfaces. EPU was upgraded to a ‘termite effective’ material by the incorporation of a synthetic pyrethroid, Bifenthrin®. Bifenthrin® was chosen over other termiticides due to its less pervasive nature to the environment along with its repellent/ killer effect on termites. The EPU/ Bifenthrin® system incorporates the specific features of durability of the polymer and slow release of Bifenthrin®, making it more acceptable to the environment and public health. Termite damage resistance of EPU was analyzed by testing the polymer, along with various other polymers (HDPE, PP, PVC and Nylon), with Coptotermes acinaciformes and correlating the termite properties (mandibular force, hardness) with those of the polymeric materials (surface and tensile properties). EPU resisted termite damage, though its softer form incurred 5 times more material damage than the robust cast type. EPUs with high values of hardness incurred ~40% less damage than HDPE and were comparable with the damages on PP. The depth and width of termite damage on HDPE was 5 and 4 times, respectively, than that of PVC. This part of the study inferred that, although hardness of polymeric materials helps prevent termite damage, toughness and resilience too can make it difficult for termites to find a pathway through the material. XPS, FTIR, termite mortality bioassays in an applied setting and elusion tests of Bifenthrin® from EPU in water, acetone and soil were employed to understand the interaction of EPU with Bifenthrin®. Water and soil were chosen as test mediums due to their practical nature. These studies confirm that Bifenthrin® at concentrations as low as 0.5 wt% enriches the surface of EPU due to preferential migration of CF3 group to the surface of EPU. Furthermore, Bifenthrin® incorporated in EPU does not compromise its insecticidal activity and diffuses in a controlled manner at the rate of ~10–8 cm2 s–1 and ~10–7 cm2 s–1 when kept in water and soil media respectively. The durability of EPU/ Bifenthrin® system was analyzed by conducting degradation studies on EPU. The effect of Bifenthrin® on the ageing of EPU was also investigated. The studies involved ageing of the system in natural and accelerated conditions and validating the results by use of Arrhenius models. The sub-soil conditions do not degrade EPU beyond the oxidative levels as the activation energy required to cause changes in properties of EPU are unphysically small (0.02 kJ mol-1). It was found that EPU can sustain its physical integrity for 12 years at room temperature and Bifenthrin® may remain in a 5 mm thick barrier material for up to 10 years. The effect of Bifenthrin® on the tensile properties of EPU is negligible. Studies to analyze the performance of the barrier material, involved testing of timber coated with the EPU/ Bifenthrin® system under real-life conditions against termites in field trials located at two tropical locations in Northern Queensland. EPU/ Bifenthrin® system with nominal concentrations of Bifenthrin® incurred no damage when the concentration of Bifenthrin® was above 0.07 wt% in EPU. The degradation of Bifenthrin® under sub-soil conditions is unlikely. Given that favourable characteristics of EPU and Bifenthrin® the design and development an effective and long-lasting termite barrier material seems feasible.

Although termites serve the ecologically important function of converting dead trees into organic matter, they annually cause damage worth billions of dollars to human structures such as houses, power poles and bridges throughout the world. This led to the development of various chemical and physical measures that primarily aimed at preventing the termites from causing damage to wooden structures. While the adverse effects of the chemical methods on the environment and human health has made them widely unacceptable, physical methods are costly and difficult to implement. There is a specific need to develop an environment friendly, cost effective, easily applicable and durable alternative barrier that would effectively protect a wide range of wooden structures. This study aims at designing and developing an eco-friendly, robust and easy to apply barrier material to protect wooden structures. Ether polyurethane (EPU) was chosen as the base material considering its toughness, resilience, hydrolytic stability due to the presence of ether group and easy applicability on large, irregular surfaces. EPU was upgraded to a ‘termite effective’ material by the incorporation of a synthetic pyrethroid, Bifenthrin®. Bifenthrin® was chosen over other termiticides due to its less pervasive nature to the environment along with its repellent/ killer effect on termites. The EPU/ Bifenthrin® system incorporates the specific features of durability of the polymer and slow release of Bifenthrin®, making it more acceptable to the environment and public health. Termite damage resistance of EPU was analyzed by testing the polymer, along with various other polymers (HDPE, PP, PVC and Nylon), with Coptotermes acinaciformes and correlating the termite properties (mandibular force, hardness) with those of the polymeric materials (surface and tensile properties). EPU resisted termite damage, though its softer form incurred 5 times more material damage than the robust cast type. EPUs with high values of hardness incurred ~40% less damage than HDPE and were comparable with the damages on PP. The depth and width of termite damage on HDPE was 5 and 4 times, respectively, than that of PVC. This part of the study inferred that, although hardness of polymeric materials helps prevent termite damage, toughness and resilience too can make it difficult for termites to find a pathway through the material. XPS, FTIR, termite mortality bioassays in an applied setting and elusion tests of Bifenthrin® from EPU in water, acetone and soil were employed to understand the interaction of EPU with Bifenthrin®. Water and soil were chosen as test mediums due to their practical nature. These studies confirm that Bifenthrin® at concentrations as low as 0.5 wt% enriches the surface of EPU due to preferential migration of CF3 group to the surface of EPU. Furthermore, Bifenthrin® incorporated in EPU does not compromise its insecticidal activity and diffuses in a controlled manner at the rate of ~10–8 cm2 s–1 and ~10–7 cm2 s–1 when kept in water and soil media respectively. The durability of EPU/ Bifenthrin® system was analyzed by conducting degradation studies on EPU. The effect of Bifenthrin® on the ageing of EPU was also investigated. The studies involved ageing of the system in natural and accelerated conditions and validating the results by use of Arrhenius models. The sub-soil conditions do not degrade EPU beyond the oxidative levels as the activation energy required to cause changes in properties of EPU are unphysically small (0.02 kJ mol-1). It was found that EPU can sustain its physical integrity for 12 years at room temperature and Bifenthrin® may remain in a 5 mm thick barrier material for up to 10 years. The effect of Bifenthrin® on the tensile properties of EPU is negligible. Studies to analyze the performance of the barrier material, involved testing of timber coated with the EPU/ Bifenthrin® system under real-life conditions against termites in field trials located at two tropical locations in Northern Queensland. EPU/ Bifenthrin® system with nominal concentrations of Bifenthrin® incurred no damage when the concentration of Bifenthrin® was above 0.07 wt% in EPU. The degradation of Bifenthrin® under sub-soil conditions is unlikely. Given that favourable characteristics of EPU and Bifenthrin® the design and development an effective and long-lasting termite barrier material seems feasible.

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Long-term declines in salmonid populations observed in California Central Valley have prompted efforts to enhance the understanding of how environmental stressors impact sensitive species. Bifenthrin, a current-use insecticide, has been consistently detected throughout the Sacramento-San Joaquin River Delta (Delta) and has been linked to detrimental effects in salmon. Traditionally, aqueous concentration is used in toxicological studies to evaluate the effects of pesticides on aquatic organisms, which assumes that concentration of the toxicant in water is a valid surrogate for dose. The critical body residue approach was established as an improved technique for assessing toxicity of hydrophobic contaminants, but there is a lack of data to support the application of this method in assessing risk of contaminant exposure in the environment. The current study creates a response spectrum model (RSM) demonstrating the relationship between internal residue and effects observed in Chinook Salmon from laboratory-based exposures. To develop the RSM, a series of behavioral and physiological endpoints were measured using bifenthrin-dosed Chinook Salmon to use with previously generated mortality data for incorporation in the model. The most sensitive endpoints were locomotion and shoaling behavior, followed by anxiety, growth, swim performance, upper thermal sensitivity, olfactory response, and lethality. The RSM endpoints were compared to bifenthrin residues in field-collected juvenile Chinook Salmon collected in 2019-2020 as part of our earlier studies. We found bifenthrin tissue residues were at similar levels to the most sensitive endpoints featured in the RSM, suggesting that bifenthrin exposure in the field is likely to cause behavioral effects to salmon as they out-migrate through the Delta. The developed RSM is a tool that could be used by water quality managers to evaluate the extent to which bifenthrin exposure may impact behavior and performance in juvenile salmon, providing a field-based verification of its effects on outmigration.

The current application of low persistence pesticides is unreliable for protecting wooden structures from termite attack. These applications may also pose an environmental and public health risk. Consequently, there is a need for the development of alternative systems to protect wooden structures from termites. Investigated here is the interaction between Australian termites, Coptotermes acinaciformis Froggatt, and to a lesser extent, Mastotermes darwiniensis Froggatt and Schedorhinotermes seclusus Hill, and a barrier system for protection of wooden structures. The aim was to develop an improved barrier for the protection of wooden structures that maximizes protection and minimizes environmental and health risks. Specifically, the performance of a barrier to protect wood against termite attack that incorporates a synthetic pyrethroid into polyurethane formulations is investigated. This research was conducted in parallel with other project contributors focusing on material science aspects of the research goals. A fundamental problem in assessing the value of termite barrier strategies lies in developing and interpreting laboratory assays that can deliver reasonable predictions of performance in the field. This is particularly the case with respect to the behaviour of termites over much longer periods in the field than can be undertaken in the laboratory. The approach to laboratory trials presented here is to define individual termite capabilities and, in combination with behavioural studies, to develop an understanding of factors which affect termite performance. The key experimental approach involved various laboratory based assays to evaluate termite foraging behaviour and performance against a range of barrier materials, progressing to field trials with the best performing material. Various species of termites; M. darwiniensis (Mastotermitidae), Cryptotermes primus (Hill) (Kalotermitidae), C. acinaciformis , Coptotermes frenchi Hill and S. seclusus (Rhinotermitidae), Microcerotermes serratus (Froggatt), Microcerotermes turneri (Froggatt) and Nasutitermes walkeri (Hill) (Termitidae) and Porotermes adamsoni (Froggatt) (Termopsidae); were investigated to determine the force that they can develop at their mandible tips. Larger termites can generate higher pressures on their mandible tips than smaller termites. By quantifying the mandible strength of a termite it was possible to contrast the capabilities of various economic termite species. Damage caused by an individual termite biting on synthetic materials was measured using electron microscope generated three dimensional models of indentations caused to the material. This was successful in quantifying the immediate capabilities of individual termites of different species. Most species were found to inflict a similar amount of damage to high density polyethylene. However M. darwiniensis caused much more damage than other species examined. Micro hardness testing was utilized to determine the relative hardness of pest termite mandibles. Termites were found to have mandibles much harder than any tested synthetic material. It was therefore found to be unrealistic to aim to develop barrier technology based on “harder than termite mandible material”. Trials using groups of termites in the laboratory demonstrated large differences in the performance of termites against various synthetic materials. There was a tendency for harder materials to suffer less damage. Mechanical properties of the barrier alone were found to be insufficient to stop termite damage. The resistance of polyurethane formulations incorporating insecticides to termite attack in the laboratory demonstrated a potential suitability for termite barrier technology. In behaviour trials, persistence of termite attack at the barrier face was found to be due not only to deterrent chemicals, but also to physical characteristics. Softer materials are not only easier for termites to remove but termites attack softer materials with greater tenacity, more termites spend more time attacking softer materials. Laboratory toxicity trials confirmed the bioavailability of Bifenthrin when incorporated within the barrier material and enabled the establishment of expected concentrations for effective protection. Termites were found to require direct contact with the barrier for mortality to occur. Trials designed to quantify repellence of the Bifenthrin in the barrier found that termites did not escape mortality by avoiding contact with the barrier material. As such pure Bifenthrin is shown to protect the barrier material directly by causing mortality rather than by repelling live termites away from the barrier. Field trials were conducted in northern Queensland where colonies of economic termites could be directly targeted. Wooden blocks were coated in polyurethane containing a range of Bifenthrin concentrations and trialed over an eight month period. Combination of the pyrethroid Bifenthrin in a polyurethane barrier at concentrations as low as 0.07% proved successful in preventing damage by the economically important termites M. darwiniensis and C. acinaciformis under high pressure field conditions. Only very small amounts of Bifenthrin migrated into adjacent soil, concentrations reached were in the order of 100 µg/kg of soil. For comparison the MLR for Bifenthrin in bananas for human consumption is 100 µg/kg. Bifenthrin in a polyurethane barrier could be used for the protection of houses and other wooden structures in the same manner as existing barrier film technology in order to minimise environmental and health risks associated with direct pesticide application techniques.

The Asian tiger mosquito, Aedes albopictus (Skuse), is a worldwide nuisance pest that is capable of vectoring several viruses of public health concern. This invasive mosquito has recently expanded its habitable range through its utilization of artificial breeding sites, often due to the activity of humans. These factors, combined with additional expansion due to global changes in climate, have led to invigorated efforts to mitigate the impact of Ae. albopictus. Because it is a diurnal species, standard mosquito control efforts utilizing spray trucks or planes to administer insecticides offer little control, as these methods are directed towards crepuscular species. Barrier spray applications, however, have been shown to achieve a significant reduction in local mosquito pressure while requiring less insecticide application. The design behind barrier sprays is to apply insecticide treatments only around areas of interest, instead of trying to eradicate the local population of mosquitoes. These studies were conducted to evaluate the efficacy of different pyrethroid barrier treatments against Ae. albopictus mosquitoes, and to examine the impact of the most effective treatment on local mosquito populations when applied to suburban residences. Three pyrethroids were examined in these studies: Demand® CS (lambda-cyhalothrin), Talstar® Professional (bifenthrin), and Suspend® Polyzone® (deltamethrin). The following factors affecting pyrethroid barrier treatments showed significant impacts on the knockdown and mortality rates of Ae. albopictus mosquitoes: the plant species, the label rate at which treatments were applied, the active ingredient used in the treatment applications, the time of exposure to the treated foliage, the presence/absence of a blood meal in the mosquito, and the time after treatment. Demand CS treatments showed the highest proportions of knockdown and mortality in adult female Ae. albopictus mosquitoes and did so for the longest amount of time, regardless of the length of the exposure time. Because the Demand CS formulation of lambda-cyhalothrin was shown to be the most effective treatment in the previous studies, it was applied as a barrier treatment to suburban residences in Roanoke, Virginia, in a field trial. Applications of Demand CS as a barrier spray were shown to significantly reduce mosquito catch numbers inside the treated barrier throughout the 8 week study, as compared to the control properties. The findings of these studies indicate that many factors, pertaining to both the insecticides used and to the environment in which they are applied, play a role in influencing the efficacy of a pyrethroid barrier treatment for the control of Aedes mosquitoes. Thus, it is important to gather relevant information before the application of a barrier spray treatment to design the most appropriate program for the situation. / Doctor of Philosophy / Mosquitoes in Virginia are capable of transmitting many different diseases to humans and livestock. Many different treatment options are available to protect humans from these populations of mosquitoes. Some of these options can be performed for a whole community, such as area-wide fogging or treatments from truck-mounted sprayers, while others are applied to properties individually, like mosquito misting systems or barrier sprays. Applying long-lasting insecticides to the edge of an area can help to protect the inside of the area from mosquitoes, and this is called barrier spraying. Barrier sprays, in particular, have become a popular choice for homeowners, and they are successful at limiting human exposure to local mosquito populations. The experiments conducted here looked at three different insecticides used in these treatments and compared them for their ability to inhibit and kill Asian tiger mosquito. Other factors that potentially influenced effectiveness were examined, such as the plant type, the length of time since the treatment was applied, and whether or not the mosquito had taken a blood meal. These experiments examined three commonly used pyrethroid insecticides to determine their efficacy against the local Asian tiger mosquito. Suspend Polyzone lasted a long time but did not produce sufficient mortality, Talstar Professional killed large numbers of mosquitoes, but for a short period, and Demand CS lasted a long time and showed a high mortality rate. These studies showed that the three different insecticides lasted on the plants for different amounts of time, but also that the insecticides needed different amounts of contact time to kill mosquitoes. This information is essential because understanding how a treatment loses effectiveness over time can help with deciding when retreatment is needed. It was also found that the different insecticides were affected by the plants that they were sprayed onto, meaning that certain insecticides did better when sprayed on specific plants. Results from these studies revealed that Asian tiger mosquitoes that had just fed on human blood were more likely to die from insecticide treatments. Thus, even if a mosquito should bite an infected person, barrier spray treatments of their property will lower the chances that the mosquito can spread the disease to other people.

The purpose of this research was to quantify properties of strandboard panels manufactured with various preservatives at loading levels effective against native termites. Panels were manufactured using nine different formulations. The method of preservative addition was also examined for some preservative formulations, increasing the total number of preservative treatments to twelve. Panels were manufactured with one target retention for each preservative treatment. An effective preservative loading relative to termites was established by previous studies or referencing current standards. Mechanical testing performed included static bending and internal bond. Physical testing included water absorption, thickness swell, and linear expansion. Few treatments met the Canadian standards for strandboard, but several preservatives performed well. Copper naphthenate, bifenthrin, and copper betaine each deserve further investigation to optimize manufacturing variables to meet required mechanical and physical properties.