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Evaluation of Six Techniques for Control of the Western Drywood Termite (Isoptera: Kalotermitidae) in Structures

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Abstract

Chemical and nonchemical methods for control of western drywood termites, Incisitermes minor (Hagen), were evaluated under conditions that simulated infestations in structures. The efficacy of excessive heat or cold, electrocution, microwaves, and 2 fumigants was evaluated. Termite mortality in artificially infested boards was 100% at 3 d after treatment for both fumigant gases. Heating the whole-structure or spot-applications using microwaves resulted in 96 and 90% mortality, respectively, 3 d after treatment. Mortality levels 4 wk after treatment increased to 98% for heat and 92% for microwaves. Spot-applications of liquid nitrogen at 381.8 kg/m3 achieved 100% mortality 3 d after treatment. However, for 122.7 and 57.3 kg/m3, mortality levels 4 wk after treatment were 99 and 87%, respectively. Mortality by spot-applications of electricity was 44% 3 d after treatment in the 1st test. Four weeks after treatment drywood termite mortality increased to 81%. In a 2nd electrocution test, using spot application techniques infrequently used in structures, mortality levels increased to 93% at 3 d and 99% at 4 wk after treatment. The distribution of termite survivors within the test building and test boards varied for some treatment techniques. For naturally infested boards, both fumigants exceeded 99% mortality. Use of heat and microwaves resulted in 100 and 99% mortality levels, respectively, 4 wk after treatment. Applications of liquid nitrogen resulted in mortality ≥99.8% at 381.8 and 122.7 kg/m3; however, mortality for 57.3 kg/m3 was significantly lower (74%). Mortality levels from electrocution were 89 and 95% 4 wk after treatment, respectively, in the 2 tests. Damage to test boards and the test building did occur. Six test boards were scorched during microwave treatment, 80% of test boards were damaged during electrocution, and visible signs of damage to the test building were noted for whole-structure heating. This study provides information for evaluation of the relative efficacy of fumigation and nonchernical alternatives for the control of drywood termite infestations in structures.
... For an alternative to fumigation, infested wood can be heated to eliminate drywood termite infestations if the wood is brought to a sufficient temperature for a long enough time (Lewis and Forschler 2014, and references therein). However, heat treatments may be impeded by structural features (heat sinks) that make it difficult to achieve the target temperatures necessary to eliminate all termites within certain pieces of wood Haverty 1996, Lewis andForschler 2014). ...
... The impact of heat sinks in whole-structure heat treatments for western drywood termite control has been previously demonstrated in an experimental structure (Lewis and Haverty 1996). Several wooden boards artificially infested with drywood termites were installed in various locations of an experimental structure, and the structure was subsequently heated with several propane heaters. ...
... The air temperature inside of heat-treated structures often reaches a level that is much higher than the target temperature. For example, Lewis and Haverty (1996) reported that the maximum air temperature in the test building reached >87°C during a heat treatment trial to achieve a target temperature of 50°C in all locations where temperatures were monitored. ...
Article
Colonies of western drywood termites, Incisitermes minor (Hagen) (Blattodea: Kalotermitidae), are difficult to detect and treat due to their cryptic nature. The use of heated air to create lethal temperatures within infested wood serves as a nonchemical treatment option targeting whole structure or large portions of the structure. However, the presence of hard-to-heat areas and potential risk of damage for heat-sensitive items are recognized as important challenges. Here, we tested if a localized injection of volatile essential oil could be utilized to address the heat sink issue, potentially increasing the overall efficiency of heat treatments against drywood termites. Artificially infested wooden blocks were placed in several locations of the test building, and heat treatments were conducted. For the treatment group, a small amount of essential oil (methyl salicylate) was added in the blocks prior to the heat treatment. All blocks placed in uninsulated wall voids had 92-100% termite mortality by day 7. However, the presence of a large concrete wall in the subarea hindered heating of blocks therein, resulting 36-44% mortality by day 7 when there was no essential oil treatment. Incorporation of the essential oil substantially increased the control efficacy for the subarea, resulting in more than 90% mortality. This approach might also be helpful in reducing the risk of potential heat damage during heat treatment without compromising its control efficacy.
... The use of pressure-treated wood (treated with chromated copper arsenate, often abbreviated as CCA) is known to deter colonization by termites (Scheffrahn et al. 1998;Scheffrahn and Su 1990). However, the In the event of inaccessible or widespread infestation of a structure, the primary method of control is fumigation (Scheffrahn and Su 1990), which involves "tenting" the structure with gas-tight tarpaulins and releasing sulfuryl fluoride (Scheffrahn and Su 1990), followed by aeration to 1 ppm or less (Lewis and Haverty 1996;Scheffrahn et al. 1997). Thermal treatments are also used, but due to technical and economic constraints, are normally not implemented for whole-house treatments, and instead are classified as compartmental treatments. ...
... Thermal treatments are also used, but due to technical and economic constraints, are normally not implemented for whole-house treatments, and instead are classified as compartmental treatments. Heat is administered using propane or electric heaters (Lewis and Haverty 1996) and is typically used on single rooms within a structure, like a single bedroom, or on single apartments in multi-family complexes. ...
... Often paired with drill-andtreat control are the spray or foam applications of borate solutions or other insecticides to susceptible raw wood surfaces, as possible preventative measures. Additional, less commonly used methods of localized treatment include the use of microwave energy to kill termites through heat in smaller areas of wood, electrocution via a handheld high-energy, low-current "gun" and the complete removal of infested wood in isolated wood structures, such as a door (Lewis and Haverty 1996). ...
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Contents: Introduction - Distribution - Description and Identification - Life History - Damage - Pest Status - Management - Selected References. This article is also published on the UF/IFAS Featured Creatures website at http://entnemdept.ufl.edu/creatures/urban/termites/heterotermes.htm.
... Microwaves are also effective for producing heat energy in a short time and are thus applied to low-water content products such as rice or cereals [3][4][5][6] . Many reports support the use of microwaves in controlling pests including termites [7][8][9][10][11][12][13][14] . Although microwaves allow efficient and rapid heating deep inside treated materials, the high-energy consumption required for optimal results is a major drawback 15,16 . ...
... Microwave heating has been traditionally used in the spot control of dry wood termites as they are classified as a single-piece infester of timbers 17 . However, this treatment method has had mixed results and some damage to test boards was noted 10 . ...
... Energy consumption for heat treatments has the potential to be considerably reduced when using microwaves 4 . During the last decade, several studies have supported the efficiency of microwave heating of wood [18][19][20][21][22][23][24][25] and wood-invading insects 7,10,11,26 . However, some other studies reported reduced or no lethal impact on pests 24,27,28 . ...
Article
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Demands for chemical-free treatments for controlling insect pests are increasing worldwide. One such treatment is microwave heating; however, two critical issues arise when using microwaves as a heat source: intensive labor and excessive energy-consumption. Optimization is thus required to reduce energy consumption while effectively killing insects. Currently, the lethal effect of microwaves on insects is considered to be due to the temperature of the irradiated materials. This study examines how the conditions of irradiation, such as resonance or traveling mode, changed the conversion of electromagnetic energy into heat when 2.45 GHz microwaves penetrated the body of the termite, C. formosanus. Our results indicated that it is possible to heat and kill termites with microwaves under resonance condition. Termites were however found to be very tolerant to microwave irradiation as the permittivity of the insect was low compared with other reported insects and plants. Electron spin resonance revealed that termites contained several paramagnetic substances in their bodies, such as Fe³⁺, Cu²⁺, Mn²⁺, and organic radicals. Interestingly, irradiation with traveling microwaves hardly produced heat, but increased the organic radicals in termite bodies indicating non-thermal effects of microwaves.
... For an additional whole-structure treatment option, heating infested wood (heat treatment) can provide effective control of drywood termites if a lethal temperature is maintained inside the wood for a sufficient amount of time (Lewis and Forschler 2014, and references therein). However, if some sections of wood are shielded from the heat by structural features that act as insulators or heat sinks, it may be difficult to achieve the target temperatures to ensure elimination of the termite colonies Haverty 1996, Lewis andForschler 2014). For example, Lewis and Haverty (1996) reported that some western drywood termites survived a heat treatment wherein the interior of the wood reached 50°C for 1 h and the air temperature of the test building reached >87°C. ...
... However, if some sections of wood are shielded from the heat by structural features that act as insulators or heat sinks, it may be difficult to achieve the target temperatures to ensure elimination of the termite colonies Haverty 1996, Lewis andForschler 2014). For example, Lewis and Haverty (1996) reported that some western drywood termites survived a heat treatment wherein the interior of the wood reached 50°C for 1 h and the air temperature of the test building reached >87°C. All of the surviving termites were found in the artificially infested pieces of wood that were placed against concrete foundations in the subarea of the test building. ...
Article
Use of heated air to create lethal temperatures within infested wood serves as a nonchemical treatment option against western drywood termites, Incisitermes minor (Hagen). When treating a whole or large portion of the structure, however, the presence of hard-to-heat areas (structural heat sinks) and potential risk of damaging heat-sensitive items are recognized as important challenges. To address these challenges, we tested if the incorporation of a volatile essential oil would increase the overall efficacy of heat treatments against the drywood termites. To choose an essential oil for use, we tested the volatile action of several candidate compounds against individual termites using a fumigant toxicity assay. As a proof-of-concept experiment, field-collected termites were housed in small wooden arenas and subsequently subjected to 2-h heat treatment at various air temperatures within a gas chromatography oven. A simulated heat sink and essential oil treatment was also included in the experimental design. Analyses of lethal temperatures (LTemp50 and LTemp99 values), probabilities of mortality, and survivorship data over time suggested that 1) the presence of a heat sink significantly increased the minimum air temperature needed for complete kill of the termites and 2) the volatile essential oil added at the site of a heat sink effectively counteracted the impact of the heat sink. The use of volatile essential oils makes it possible to effectively kill drywood termites even in areas which might not reach lethal temperatures (~50°C), potentially improving the overall efficacy of heat treatments while reducing the risk of heat damage.
... While these treatments are highly effective when properly delivered, they do not prevent reinfestation. They are also costly, difficult to handle, and in the case of methyl bromide, under considerable regulatory pressure because of the reported effects on the ozone layer (Lewis et al. 2014;Ristaino and Thomas 1997). The development of alternative WIDT treatments would help reduce costs and potential environmental impacts while enhancing safety. ...
Article
West Indian drywood termites (Cryptotermes brevis, Blattodea: Kalotermitidae) are an important invasive termite in many countries including Australia where they are spreading across two eastern states. Fumigation is often used to eliminate infestations, but it is costly, has negative environmental effects and does not prevent reinfestation. Heat treatment has been suggested as an alternative. Many insect pest mitigation strategies recommend 30 min exposure at 56 °C, but this may be difficult to achieve in structural applications. The potential for heating at lower temperatures was explored to determine the effect on termite survival and gut fauna. Exposure to 40 °C up to an hour did not kill the termites; however, 1-h exposure at 45 °C was lethal. Exposure for little as 3 min at 50 °C or 2 min at 55 °C was lethal. Protozoa levels were lower in termites that survived shorter exposures, but there appeared to be some recovery over time. The results suggest that short term exposures to 50 or 55 °C could be used to eliminate infestations, creating an opportunity for localized spot heating as a mitigation measure.
... One of the challenges in performing an efficacious heat treatment is the presence of structural heat sinks or difficult-to-heat areas [24,25]. These areas may be found in concrete, tile, or insulating materials contacting the target wood members. ...
Preprint
With heat treatments to control drywood termites (Blattodea: Kalotermitidae), the presence of heat sinks causes heat to be distributed unevenly throughout the treatment areas. Drywood termites may move to galleries in heat sink areas to avoid exposure to lethal temperatures. Our studies were conducted in Crytotermes brevis-infested condominiums in Honolulu, Hawaii to reflect real-world condominium scenarios; either a standard heat treatment performed by a heat remediation company or an improved heat treatment was used. For improved treatments, heated air was directed into the toe-kick voids of C. brevis infested cabinets to reduce heat sink effects and increase the heat penetration into these difficult-to-heat areas. Eight thermistor sensors placed inside toe-kick voids, treatment zone, embedded inside cabinets’ sidewalls, and in a wooden cube recorded target temperatures of above 46 °C or 50 °C for 120 minutes. A pretreatment and follow-up inspections were performed at 6 months posttreatment to monitor termite inactivity using visual observations and by recording the numbers of spiked peaks on a microwave technology termite detection device (Termatrac). In improved treatment condominiums, significantly higher numbers of spiked peaks were recorded at pretreatment as compared to 6 months posttreatment. Efficacious heat treatment protocols using the improved methods are proposed.
... One of the challenges in performing an efficacious heat treatment is the presence of structural heat sinks or difficult-to-heat areas [24,25]. These areas may be found in concrete, tile, or insulating materials contacting the target wood members. ...
Article
Full-text available
With heat treatments to control drywood termites (Blattodea: Kalotermitidae), the presence of heat sinks causes heat to be distributed unevenly throughout the treatment areas. Drywood termites may move to galleries in heat sink areas to avoid exposure to lethal temperatures. Our studies were conducted in Crytotermes brevis-infested condominiums in Honolulu, Hawaii to reflect real-world condominium scenarios; either a standard heat treatment performed by a heat remediation company, or an improved heat treatment was used. For improved treatments, heated air was directed into the toe-kick voids of C. brevis infested cabinets to reduce heat sink effects and increase heat penetration into these difficult-to-heat areas. Eight thermistor sensors placed inside the toe-kick voids, treatment zone, embedded inside cabinets’ sidewalls, and in a wooden cube recorded target temperatures of above 46 ◦C or 50 ◦C for 120 min. Pre-treatment and follow-up inspections were performed at 6 months posttreatment to monitor termite inactivity using visual observations and by recording the numbers of spiked peaks on a microwave technology termite detection device (Termatrac). In improved treatment condominiums, significantly higher numbers of spiked peaks were recorded at pre-treatment as compared to 6 months posttreatment. Efficacious heat treatment protocols using the improved methods are proposed.
... One of the challenges in performing an efficacious heat treatment is the presence of structural heat sinks or difficult-to-heat areas [23,24]. These areas may be found in concrete, tile, or insulating materials contacting the target wood members. ...
Preprint
With heat treatments to control drywood termites (Blattodea: Kalotermitidae), the presence of heat sinks, which have insulating properties, causes heat to be distributed unevenly throughout the treatment areas. Drywood termites may move to galleries in heat sink areas to avoid exposure to lethal temperatures. To mitigate heat sink effect, studies were conducted in Crytotermes brevis-infested homes in Honolulu, Hawaii to reflect real-world scenarios; either a standard heat treatment performed by a heat remediation company or improved heat treatment methods were used. For improved treatments, heated air was directed into the toe-kick voids of cabinets to reduce heat sink effects. Eight thermistor sensors were placed inside toe-kick voids, in the treatment zone, embedded inside cabinets or the sidewall, or in a wooden cube to monitor internal and ambient temperatures to ensure sufficiently high heat reached all areas. Target temperatures above 46 °C or 50 °C were recorded in all areas for 120 minutes. A pretreatment inspection was conducted, and follow-up inspections were performed at 6 months posttreatment to confirm termite inactivity using visual observations and a Termatrac device. In improved treatment homes, no termite activity was found after treatment. Efficacious heat treatment protocols for structures using the improved method are proposed.
... In this respect, Burdette et al. (1975) reported that microwave technology using for wood products to control borers infestations, while Lewis and Haverty (1996); Lewis et al. (2000); Peters andCreffield (2002) andEvans (2002) showed that microwave irradiation used to control for dry wood termite. Also, Fleming et al. , 2005 andKisternaya andKozlov, 2007 showed that the irradiation of microwave has been successfully used for many years for attacked wood treatment by wood borers. ...
Article
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Dry wood termite, Cryptotermes brevis Walker (Isoptrea: Kalotermitidae) is a serious pest attack the different kinds of hard and soft wood of wooden structures, standing trees, flooring, furniture, wooden works within buildings in different images and shapes , etc. Three different methods to control C. brevis termite within two kinds of wood (pine and beech) were used in this work; these are microwave radiation, high temperature and cooling degrees. The effects of these methods on the percentages of mortality are correlated with exposure times of infested wood (pine and beech) to each method. The least exposure time which gave 100% mortality differed according to used method. In microwave method, the shortest exposure time which gave 100% mortality recorded 20 sec. with power level 100 wattages for termite within pine wood while, required 80 wattages with beech wood, the longest exposure time which appeared100% mortality was 50 sec. for pine wood at 50wattages, while it was 60sec. at the power level 10 wattages for beech wood. In cooling method, the percentage of mortality recorded 100% at-27°C with 18Min.exposure time for pine wood and 20Min. for beech wood, while at-21°C the exposure time was 30 and 32Min. for pine and beech wood, respectively, whereas at-18°C the exposure time was 36 and 40Min. for pine and beech wood, respectively. In heating method, the shortest exposure time (for 100% mortality) recorded 28 Min. at 75°C for both pine and beech wood, while at 70°C the time was 34 Min. for both pine and beech wood, whereas the exposure times at 65 °C recorded 34 and 35Min.for pine and beech wood respectively. The longest exposure time reached 35Min at 60°C for two kind wood. The lethal time values (LT50 and LT95) were determined for the different treatments in different methods of control. The lost moisture content from infested wood exposure to both microwave irradiation and different temperature degrees was significant correlated with exposure time and showed changes in mortality percentages. Therefore, the combined effect of each temperature and lost moisture content play an important role beside exposure times and wood kind in effect on mortality of termite within infested wood. .
Article
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Exposure of pecan-weevil-infested in-shell pecans of 6. 1% kernel moisture to 43-MHz dielectric heating treatments for 25 s killed all of the larvae in the pecans. Similar treatment of larvae in pecan kernel pieces of 2. 6% moisture provided complete control with shorter exposures and lower temperatures in the pecans. Microwave heating treatments at 2450 MHz were somewhat less effective in controlling pecan weevil larvae in broken pieces of pecan kernels and shells than were 40-MHz treatments of the same materials.
Article
The influence of physiological stage and age was examined in pupae of 1–4-8 days-old and adults of 2–9 days-old of Ceratitis capitata. Flies were irradiated with microwaves at 9 GHz in a rectangular waveguide applicator with a power density of 8.6 W/cm² and exposure times ranging from 7.5 s to 2.25 min. Data could be represented by parallel probit-log dose lines of common slope b= 6.127 ± 0.283. Significant differences among all lines were obtained at the 0.05 level. The susceptibility to microwave exposure was higher in adult flies than in pupae. The sequence of tolerance was 4 > 8 > 1 (pupae) > 2 > 9 (adults). The TL50 extreme values in minutes were 0.155 to 9 days-old adults and 1.089 to 4 days-old pupae. Pupae sensibility to microwaves was related to weight loss during the treatment. The high weight loss was recorded on 1 day-old pupae which were the most susceptible to radiation in the pupal stage. Reciprocity law was also studied on adults of 2–9 days-old irradiated at 9 GHz and power densities of 4.3 and 8.6 W/cm². In C. capitata we found that high power densities and short exposure times were the most effectives.