Termite (order Blattodea, infraorder Isoptera) baiting 20 years after commercial release

Zinc 1,1,2,2-Tetrafluoroethanesulfinate: A Synthetically Useful Oxidative and Photoredox Source of the 1,1,2,2-Tetrafluoroethyl Radical

1,1,2,2-Tetrafluoroethyl-containing molecules are of potential importance in drug discovery, but the efficient synthesis of such compounds is still relatively unexplored due to the lack of readily available reagents for the incorporation of the HCF2CF2 group. Herein, we introduce a new reagent, zinc 1,1,2,2-tetrafluoroethanesulfinate, which can be useful for the oxidative tetrafluoroethylation of arylboronic acids and heteroarenes as well as for a novel photoredox, three component hydro-tetrafluoroethylation of two alkenes of complementary reactivity.

Controllable Double Difluoromethylene Insertions into S-Cu Bonds: (Arylthio)tetrafluoroethylation of Aryl Iodides with TMSCF2Br

A new method of constructing "ArSCF2CF2Cu" from ArSCu and TMSCF2Br (TMS=trimethylsilyl) has been developed. The cross-coupling reactions of the obtained "ArSCF2CF2Cu" with diverse aryl iodides (Ar'I) provide an efficient access to Ar'CF2CF2SAr. Mechanistic studies demonstrate that the "ArSCF2CF2Cu" species were generated through controllable double difluoromethylene insertions into ArS-Cu bonds rather than the 1,2-addition of ArSCu to tetrafluoroethylene.

Feeding cessation after feeding on 20-hydroxyecdysone in the Formosan subterranean termite

BACKGROUND

To control subterranean termite pests, chitin synthesis inhibitor (CSI) baits have been widely applied. Despite CSI baits having low impacts on the environment, they require a lengthy time period to eliminate colonies. 20-hydroxyecdysone (20E) was proposed to speed up the baiting process as it showed faster mortality than CSI baits. However, the efficacy of 20E has previously not been tested at the colony level prior to applying in the field.

RESULTS

We compared the effect of 20E, 20E + noviflumuron, noviflumuron and untreated control using colonies of Coptotermes formosanus. Our result revealed that both 20E and 20E + noviflumuron did not accelerate colony elimination and termite activity remained relatively stable during the observation periods. To determine the limited effects of 20E, we further investigated feeding duration and consumption amount of 20E with different concentrations (control, 100 and 1000 ppm) for 10 days. Termites ceased feeding after 1 day in 100 and 1000 ppm treatment and 100% mortality was observed within 10 days in 1000 ppm 20E, while mortality in the 100 ppm 20E treated group was much lower than that in the 1000 ppm group. Furthermore, no termites molted in the control and termites died from hyperecdysonism in 1000 ppm 20E treatment, whereas about 20% of termites molted in 100 ppm 20E.

CONCLUSION

This study demonstrated that 20E may not be suitable as a sole active ingredient to accelerate elimination of a subterranean termite colony, while CSI baits and lower concentrations of 20E may reduce the lengthy time period in colony elimination. © 2023 Society of Chemical Industry.

Visible-Light-Induced Three-Component Tetrafluoroethyl-heteroarylation of Alkenes with 1,1,2,2-Tetrafluoroethanesulfonyl Chloride and Quinoxalin-2(1H)-ones

1,1,2,2-Tetrafluoroethyl-containing compounds are valuable structures due to their unique physicochemical properties, which have increasing potential application in drug discovery. However, synthetic methods for preparing such compounds are rare. Herein, we report the first use of 1,1,2,2-tetrafluoroethanesulfonyl chloride to introduce the HCF2 CF2 group into organic molecules via a three-component, radical tetrafluoroethyl-heteroarylation of alkenes with readily available quinoxalin-2(1H)-ones. This method provides a new and facile approach for late-stage functionalization of potential biologically active molecules.

Controllable Single and Double Difluoromethylene Insertions into C-Cu Bonds: Copper-Mediated Tetrafluoroethylation and Hexafluoropropylation of Aryl Iodides with TMSCF2H and TMSCF2Br

The selective difluoromethylene insertion into a C-Cu bond is a challenging task and is currently limited to either a single CF₂ insertion into CuCF₃ or double CF₂ insertions into CuC₆F₅ (or (Z)-CF₃CF = CFCu). Achieving both selective single and double CF₂ insertions into the same C-Cu bond is even more difficult. Herein, highly controllable single and double CF₂ insertions into CuCF₂H species with a TMSCF₂Br reagent have been described, affording two previously unknown fluoroalkylcopper species "Cu(CF₂)_nCF₂H" (n = 1 and 2) independently under different reaction conditions. This work represents the first example of both single and double CF₂ insertions into the same C-Cu bond in a highly selective manner. The synthetic value of the obtained "Cu(CF₂)_nCF₂H" (n = 1 and 2) species is demonstrated by their reactions with aryl iodides, halogenation agents, and cinnamyl chloride, which enables the direct transfer of HCF₂CF₂ and HCF₂CF₂CF₂ moieties into organic molecules. The key to controllable fluorocarbon chain elongation from C₁ to C₂ and from C₁ to C₃ is presumably attributed to the different reactivities of "Cu(CF₂)_nCF₂H" species (n = 0, 1, 2 and 3) and the loading of the TMSCF₂Br reagent.

Installation Season May Significantly Impact Time Required for Subterranean Termites to Find and Feed on In-Ground Baits

Simple Summary

Insecticide baits for use against subterranean termites have been shown to be highly effective, but the time required for termites to find and feed on baits may be a barrier to adoption in some areas. One explanation for this “time-to-attack” problem is that termite foraging near the soil surface may be limited during inhospitable periods. In California, characterized by a hot-summer Mediterranean climate, western subterranean termites have mostly been observed near the surface during the wet season, suggesting that baits installed in summer may sit uninvestigated for many months. To test this hypothesis, we established research plots in areas of known termite incidence, installing baits on four different dates over a one-year period and then recording termite activity every 60 days for two years. As expected, most foraging in these stations was observed in winter and spring. Time-to-attack for stations installed at the beginning of winter was significantly less than for stations installed at the beginning of summer (194 d vs. 296 d). These findings may help pest control operators in regions with pronounced dry periods to optimize their use of bait station systems by targeting specific installation seasons.

Abstract

Rhinotermitid termites, serious pests of wooden structures throughout the world, are commonly controlled with chitin synthesis inhibitor bait systems. Seasonal termite foraging patterns in some regions may prolong bait interception time, however, significantly decreasing colony elimination speed. We hypothesized that installing baits immediately prior to the season of highest foraging activity will minimize interception time when baiting for Reticulitermes spp. in California, a region characterized by a hot-summer Mediterranean climate. To test this theory, we installed three different bait systems on four dates corresponding to the major seasons (spring, summer, autumn, winter) at five field locations known to harbor the target species. We then recorded initial termite discovery events every 60 days for two years, considering effects of installation season, bait system, site, and distance from previously observed termite incidence on bait interception time. Observed foraging activity in bait stations was highest during late winter and spring. Baits installed during winter exhibited interception times more than 100 days shorter than those of baits installed during summer. From these findings, we conclude that colony elimination speed and perceived CSI bait utility may be increased in Mediterranean climate regions when baits are installed immediately prior to the wet season.

A Review of the Evolution of Termite Control: A Continuum of Alternatives to Termiticides in the United States with Emphasis on Efficacy Testing Requirements for Product Registration

The global economic impact of termites is estimated to be approximately USD 40 billion annually, and subterranean termites are responsible for about 80% of the total impact. Twenty-eight species of termites have been described as invasive, and these termites are spreading, partially due to global trade, making effective control methods essential. Termite control is complex, as is the biology and behavior of this social insect group. In the U.S., termite prevention and control (with claims of structural protection) is regulated by more than one industry (pest control and building construction), and at the federal and state levels. Termite prevention has historically relied on building construction practices that do not create conducive conditions for termite infestations, but as soil termiticides developed, heavy reliance on pesticides became the standard for termite control. The concern for human and environmental health has driven the development of termite control alternatives and regulation for products claiming structural protection. Product development has also provided unprecedented opportunities to study the biology and behavior of cryptobiotic termites. Technological advances have allowed for the re-examination of questions about termite behavior. Advances in communications via social media provide unrestricted access to information, creating a conundrum for consumers and science educators alike.

Area-population control of fungus-growing termite, Odontotermes formosanus, using hexaflumuron durable baits

BACKGROUND

Fungus-growing termites (Termitidae: Macrotermitinae) are common forest and agriculture pests. To evaluate the efficacy of termite baiting in suppressing field population of fungus-growing termites, a durable termite bait with hexaflumuron was evenly installed in a one-hectare forest area dominated by a fungus-growing termite, Odontotermes formosanus (Shiraki). Monthly monitoring of termite foraging activity on baits and wood stakes was conducted for 4 years to quantify efficacy of baits. To examine whether the hexaflumuron led to colony death, pesticides in fungus gardens of active and deceased nests were quantified using a LC-QTOF/MS.

RESULTS

After baiting, 50% and 90% of baits were fed upon 10 and 24 months, respectively. After 2 years of baiting, the monthly number of wood stakes occupied by termites was reduced from 34.7 ± 1.8 to 17.6 ± 2.5 (-49.1%), and the number of wood stakes consumed was reduced from 17.7 ± 0.8 to 13.3 ± 1.2 (-25.7%). Hexaflumuron was detected in deceased colonies, including five of six fungus gardens and the fungal tissue of Xyleria grown on fungus gardens, with a concentration of 0.31-20.11 mg kg^-1 dry weight.

CONCLUSION

This study demonstrated that durable hexaflumuron baits consumed by fungus-growing termites were further incorporated into fungus gardens, resulted in colony elimination and negative area-population effects, supporting that durable hexaflumuron baits are effective in suppressing field populations of fungus-growing termites. © 2021 Society of Chemical Industry.

Queen Egg Laying and Egg Hatching Abilities are Hindered in Subterranean Termite Colonies When Exposed to a Chitin Synthesis Inhibitor Bait Formulation

Subterranean termite control methods using chitin synthesis inhibitors (CSIs) aim at eliminating colonies that feed upon a bait formulation. Several benzoylurea active ingredient formulations are currently commercially available as alternative termite management strategies to liquid termiticides. Individual workers need to molt on a regular basis and CSIs interfere with such molting process, allowing sufficient time for the acquisition of a colony-wide lethal dose prior to widespread mortality. As workers progressively die, the colony eventually collapses, leaving only soldiers and primary reproductives that starve to death. One common observation is that young workers often die early owing to their relatively short molting cycle. However, the absence of brood in dying colonies raises questions about the potential fate of eggs laid by the queen. This study aims to determine if CSI baits also terminate the ability of a colony to produce a new cohort of workers by disabling the ongoing brood development. Incipient termite colonies were used to test the impact of noviflumuron on the queen's ability to lay eggs and on the eggs' ability to hatch. Our results showed that queens in colonies exposed to CSI not only initially laid less eggs than the control queens, but eggs also did not develop and were progressively cannibalized, eventually leading to colony establishment failure. This result implies that queens of mature colonies exposed to CSI would lose the ability to lay viable eggs as the colony collapses, leading to an absence of worker replacement, aiding in colony elimination.

Subterranean Termite (Coptotermes gestroi (Blattodea: Rhinotermitidae)) Colony Elimination Through Exposure to a Novaluron CSI Bait Formulation in Laboratory

The development of baits for subterranean termite control over the past 25 yr has provided cost-effective alternatives to liquid termiticide treatments. Current bait products use one of the few available benzoylurea chitin synthesis inhibitors (CSIs) labeled for subterranean termites. These insecticides are used because of their nonrepellency, their slow-acting mode of action, and their dose-independent lethal time. Although many studies have provided ample evidence of the efficacy of CSI baits for subterranean termite colony elimination, most have focused on hexaflumuron and noviflumuron. However, bait products using alternative CSIs have not received the same level of scrutiny, limiting the amount of evidence proving their efficacy. One such compound is novaluron, the active ingredient currently used in the Trelona ATBS-Advance Termite Baiting System bait product. The current study independently tested the efficacy of this commercially available bait formulation against whole colonies of Coptotermes gestroi (Wamann) (~63,910 workers) in the laboratory, using an extended experimental setup to simulate a 15-m foraging distance from the central part of the nest to the bait, while having access to alternative food sources. Treated colonies progressively ceased to feed on wood items within 45 d after being provided access to the novaluron bait formulation, with a subsequent progressive collapse of the population, leading to colony elimination by 91 d. This study therefore confirms the efficacy of novaluron baits against subterranean termites, and currently remains one of the few CSIs that can be applied for the successful control of Coptotermes infestations.

Foraging behavior and bait station preference in scavenging termite, Odontotermes obesus (Blattodea: Termitidae)

Termites are a significant pest of buildings, agriculture, and trees, and are mainly controlled by baiting. However, baiting systems are available for only lower termites (Rhinotermitidae) not for higher termites (Termitidae). Termite foraging behavior associated with baiting systems varies among species and families, and plays a significant role in baiting success. Here, foraging behavior of Odontotermes obesus (Blattodea: Termitidae: Macrotermitinae), a fungus-growing higher termite, was investigated relative to three bait-station sizes (small, medium, and large) containing different quantities of food. Significantly more workers recruited to large stations (470/station) compared to medium (246/station) and small (124/station) stations. Abundance of O. obesus in large and medium stations significantly positively correlated with relative humidity whereas negative but non-significant correlations were observed with temperature in large and medium stations. Total and continuous contacts with the stations increased with time and were greater in large stations. Station abandonment due to disturbance was significantly less in large stations (3%) followed by medium (9%) and small stations (20%). Our results suggest that large stations (≈8 litres volume) work best for population management of O. obesus and other related fungus-growing higher termites.

Termite Assemblage and Damage on Tree Trunks in Fast-Growing Teak Plantations of Different Age: A Case Study in West Java, Indonesia

We conducted surveys of termite assemblages and tree trunks damaged by termites in teakwood (Tectona grandis L.f.) plantations. The surveys were conducted in five-, six-, and nine-year-old plantations. We used a standardized belt-transect to collect termites and build tree inventories. Data of collected termites at the genus and functional-group levels and termites' diversity between plantations were compared with their attack rate. The results showed that four genera of soil recycler termites belonging to groups IIf and III were present across the plantations. Distribution analysis suggested that termite communities might develop from a stochastic distribution to a nonrandom co-occurrence distribution over time. Diversity analysis showed an increased nestedness-resultant diversity contribution to the total dissimilarity over time. Observed attacks on tree trunks were superficial and limited to the outer bark, with group IIf as the main contributor. Furthermore, the level of damage done by termites to tree trunks was positively correlated with increases in the group IIf occupancy area and overgrown understory vegetation. Plantation management by maintaining an adequate understory might suppress termite attacks on fast-growing teakwood, although in the case of our study, termite attacks are inevitable when termites from group IIf were already present.

Concentration-Dependent Feeding Deterrence to 20-Hydroxyecdysone for Three Subterranean Termite Species (Blattodea: Rhinotermitidae)

Simple Summary

Subterranean termite colonies can be eliminated using baiting systems. However, for a given bait to be effective, the active ingredient must be lethal at concentrations that are also palatable to termites. The insect molting hormone, 20-hydroxyecdysone (20E), has potential for use in termite baits, but its palatability to termites has not been examined. The purpose of this study was to determine what concentrations of 20E, if any, cause termite workers to feed less readily. To test this, paper disks were treated with various concentrations of 20E. Groups of 1000 termites of three different species; the Formosan, the Asian and the Eastern subterranean termite; were placed in arenas. The termites had the option of following a path to feed on either a paper disk containing the 20E, or an untreated disk, and the amount of paper consumed was then compared. The results showed that the Asian subterranean termite had the least tolerance for the 20E, the Formosan subterranean termite had a reduced tolerance, and the presence of the 20E had no impact on the Eastern subterranean termite.

Abstract

Effective active ingredients in toxicant bait formulations must be non-deterrent to insect feeding behavior at lethal concentrations. This study evaluated feeding deterrence for Coptotermes formosanus Shiraki, C. gestroi (Wasmann), and Reticulitermes flavipes (Kollar) when provided access to cellulose impregnated with various concentrations of the insect molting hormone, 20-hydroxyecdysone (20E). Termites were exposed to 20E concentrations of 200, 500, 1000 and 2000 ppm and to noviflumuron at 5000 ppm in a 24 h choice-test, and the mass of substrate consumption from treated and untreated media pads was compared for each treatment. 20E feeding deterrence was detected at 500, 1000 and 2000 ppm for C. gestroi, and at 2000 ppm for C. formosanus. No significant differences in consumption of treated and untreated substrate was detected at any concentration for R. flavipes. Potential methods for reducing deterrence are discussed.

Area-Wide Elimination of Subterranean Termite Colonies Using a Novaluron Bait

We investigated the use of termite baiting, a proven system of targeted colony elimination, in an overall area-wide control strategy against subterranean termites. At two field sites, we used microsatellite markers to estimate the total number of Reticulitermes colonies, their spatial partitioning, and breeding structure. Termite pressure was recorded for two years before and after the introduction of Trelona® (active ingredient novaluron) to a large area of one of the sites. Roughly 70% of the colonies in the treatment site that were present at the time of baiting were not found in the site within two months after the introduction of novaluron. Feeding activity of the remaining colonies subsequently ceased over time and new invading colonies were unable to establish within this site. Our study provides novel field data on the efficacy of novaluron in colony elimination of Reticulitermes flavipes, as well as evidence that an area-wide baiting program is feasible to maintain a termite-free area within its native range.

Effects of clay materials and moisture levels on habitat preference and survivorship of Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae)

Formosan subterranean termites, Coptotermes formosanus Shiraki, usually transport clay materials into tree hollows and bait stations. Our previous research showed that C. formosanus preferred to aggregate in the locations containing field-collected clay samples, but it was not clear whether this preference was influenced by clay types and/or moisture. In the present study, we conducted multiple-choice tests under low-moisture (25% moisture) or moderate-moisture (50% moisture) conditions to evaluate the aggregation and wood-feeding preferences of C. formosanus responding to hollow wooden cylinders (simulation of tree hollows) or baiting containers (simulation of bait stations) filled with different clay materials (bentonite , kaolin, chlorite, illite, or attapulgite), soil, or unfilled. Under low-moisture conditions, the majority of termites were found in the wooden cylinders or baiting containers filled with bentonite. Under moderate-moisture conditions, however, termites preferred to aggregate in wooden cylinders filled with chlorite or attapulgite; the percentages of termites that stayed in baiting containers filled with chlorite, attapulgite or soil were similar, which were significantly higher than those that filled with kaolin, illite, or unfilled. We then conducted no-choice tests to study the effect of clay materials on termites. Under low-moisture conditions, clay filled in the baiting containers significantly increased survivorship and body water percentage (an indicator of termite vigor) of termites, whereas no similar effect was detected under moderate-moisture conditions. This study demonstrated that both clay type and moisture affect termites' preference.

Ovarian Transcriptomic Analyses in the Urban Human Health Pest, the Western Black Widow Spider

Due to their abundance and ability to invade diverse environments, many arthropods have become pests of economic and health concern, especially in urban areas. Transcriptomic analyses of arthropod ovaries have provided insight into life history variation and fecundity, yet there are few studies in spiders despite their diversity within arthropods. Here, we generated a de novo ovarian transcriptome from 10 individuals of the western black widow spider (Latrodectus hesperus), a human health pest of high abundance in urban areas, to conduct comparative ovarian transcriptomic analyses. Biological processes enriched for metabolism—specifically purine, and thiamine metabolic pathways linked to oocyte development—were significantly abundant in L. hesperus. Functional and pathway annotations revealed overlap among diverse arachnid ovarian transcriptomes for highly-conserved genes and those linked to fecundity, such as oocyte maturation in vitellogenin and vitelline membrane outer layer proteins, hormones, and hormone receptors required for ovary development, and regulation of fertility-related genes. Comparative studies across arachnids are greatly needed to understand the evolutionary similarities of the spider ovary, and here, the identification of ovarian proteins in L. hesperus provides potential for understanding how increased fecundity is linked to the success of this urban pest.

Progress and prospects of arthropod chitin pathways and structures as targets for pest management

Chitin is a structural component of the arthropod cuticular exoskeleton and the peritrophic matrix of the gut, which play crucial roles in growth and development. In the past few decades, our understanding of the composition, biosynthesis, assembly, degradation, and regulation of chitinous structures has increased. Many chemicals have been developed that target chitin biosynthesis (benzoyphenyl ureas, etoxazole), chitin degradation (allosamidin, psammaplin), and chitin regulation (benzoyl hydrazines), thus resulting in molting deformities and lethality. In addition, proteins that disrupt chitin structures, such as lectins, proteases, and chitinases have been utilized to halt feeding and induce mortality. Chitin-degrading enzymes, such as chitinases are also useful for improving the efficacy of bio-insecticides. Transgenic plants, baculoviruses, fungi, and bacteria have been engineered to express chitinases from a variety of organisms for control of arthropod pests. In addition, RNA interference targeting genes involved in chitin pathways and structures are now being investigated for the development of environmentally friendly pest management strategies. This review describes the chemicals and proteins used to target chitin structures and enzymes for arthropod pest management, as well as pest management strategies based upon these compounds, such as plant-incorporated-protectants and recombinant entomopathogens. Recent advances in RNA interference-based pest management, and how this technology can be used to target chitin pathways and structures are also discussed.

Acute Toxicity and Sub-lethal Effects of the Essential Oil of Aristolochia trilobata and Its Major Constituents on Nasutitermes corniger (Termitidae: Nasutitermitinae)

Nasutitermes corniger (Motschulsky, 1855) (Termitidae: Nasutitermitinae) is an important pest in urban environments and bioinsecticides can be an alternative to its control. Here, we determined the toxicity and repellence of the essential oil (EO) prepared from stems of Aristolochia trilobata L. (Aristolochiaceae) and its major constituents on N. corniger. We also investigated behavioral changes of individuals exposed to limonene. The lethal dose required to kill 50% of N. corniger population (LD₅₀) of EO of A. trilobata was 2.44 μg mg^-1. Limonene was the most toxic compound to N. corniger followed by linalool (LD₅₀ = 1.02 and 1.29 μg mg^-1, respectively). In addition, all treatments presented median lethal time (LT₅₀) less than 11 h. A. trilobata EO and its constituents showed irritability activity, but only limonene repelled soldiers more than workers. The negative behaviors of N. corniger groups were higher in individuals treated with limonene. A. trilobata EO and its constituents, especially the limonene, are promising for the control of N. corniger due the high toxicity, repellence, and possible disturbance in the colonies.

Effect of Polyacrylamide/Attapulgite Composite on Foraging Behaviors of Formosan Subterranean Termites (Blattodea: Rhinotermitidae)

Moisture conditions of food and soil are essential for the survival and foraging activities of subterranean termites. Polyacrylamide/attapulgite composite is a water-retaining agent that has been applied to increase moisture of agricultural soils. We hypothesize that polyacrylamide/attapulgite composite may increase the moisture of bait matrixes and soil surrounding baiting containers and therefore attract termites and increase their foraging activities. In the present study, aggregation and feeding preferences, survivorship, body water percentage, and wood consumption of Formosan subterranean termites, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), were investigated when responding to polyacrylamide/attapulgite composite that was buried within soil (substrate) or filled in the void volume of baiting containers. Two-choice tests showed that termites consumed significantly more wood when polyacrylamide/attapulgite composite was buried within dry soil (27%-moisture) than the controls (no polyacrylamide/attapulgite composite was provided). However, polyacrylamide/attapulgite composite buried within wet soil (54%-moisture) did not significantly affect foraging behaviors of termites. Multiple-choice tests showed no aggregation or feeding preference of termites in the baiting containers filled with polyacrylamide/attapulgite composite compared with the soil-filled or unfilled ones, whenever the substrate was dry or wet. No-choice tests showed that the presence of polyacrylamide/attapulgite composite (buried within soil or filled in baiting containers) significantly increased wood consumption and body water percentage of termites as well as wood moisture under dry-substrate conditions. Our studies suggest that burying polyacrylamide/attapulgite composite within dry soil may enhance foraging activities of termites, but filling the bait stations with polyacrylamide/attapulgite composite may not effectively attract termites.

Development of Baits for Population Management of Subterranean Termites

The objective of bait application envisioned by early researchers was to eliminate the source of infestation, the colony, but because of the lack of adequate evaluation tools, results of field trials with mirex baits in the 1960s were mostly inconclusive. On-the-ground monitoring stations and mark-recapture protocol developed in the 1970s marked the turning point in the field studies of termite baits. Results of field studies with metabolic inhibitors and chitin synthesis inhibitors (CSIs) in the 1990s indicated that a bait toxicant has to be slow-acting and nonrepellent, and its lethal time has to be dose independent. A recent discovery that termites return to the central nest to molt and CSI-poisoned termites die near the royal pair further explains the success of CSI baits in eliminating colonies. Owing to the availability of durable baits that require less-frequent site inspection, more termite control professionals have adopted baiting systems in recent years.

Filling Voids in Subterranean Termite (Blattodea: Rhinotermitidae) Bait Stations With Soil or Clay Improves Preference and Performance

Subterranean termites often transport soil into bait stations. In this study, we hypothesize that adding soil or clay material in the bait may affect preference and performance of termites. Choice and no-choice tests were conducted in the laboratory to investigate the aggregation and feeding preference, survivorship, wood consumption, and body water percentage of termites in response to food containers (here we simulated the bait station by placing a wood block into a bigger plastic box with termite-entering holes on the wall) with the void space filled with soil (sandy clay loam), clay material (sodium bentonite), or remained unfilled. Choice tests showed that under low-moisture conditions, food containers filled with clay attracted significantly more termites (Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae) and Reticulitermes guangzhouensis Ping (Blattodea: Rhinotermitidae)) compared to food containers filled with soil, or unfilled. Under medium-moisture conditions, however, the percentages of termites that aggregated in the food containers filled with soil or clay were similar, and both were significant higher than the percentages in unfilled ones. In no-choice tests, the highest survivorship and wood consumption in C. formosanus were recorded under medium-moisture conditions and when food containers were filled with clay, whereas the lowest survivorship and wood consumption were recorded under low-moisture conditions and when food containers were filled with soil. Interestingly, presence of clay increased the body water percentage of termites. Our study enhances the understanding of the foraging ecology of subterranean termites, and may contribute to the improvement of termite-baiting technologies.

Field Evaluations of Fluid Baits against Colonies of the Formosan Subterranean Termite (Blattodea:Rhinotermitidae)

Fluid baits comprised of 10% dry medium (impregnated with 0.5% hexaflumuron) and 90% methylcel solution were injected into foraging galleries of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), in trees and buildings. Elimination times at two of the six baited sites were longer than expected, possibly due to the application disturbance or the presence of an old and declining colony, but fluid bait treatments eliminated all baited colonies. Fluid baits were injected through drill holes behind infested wood surface, and bypassed the difficulties for installing above-ground (AG) bait stations on uneven surface or at tight corners. Because a large quantity of fluid baits could be applied at once, termite control professionals may be able to avoid revisiting the site to add more baits. The absence of unsightly AG station in a house will also make fluid baits more acceptable to homeowners than AG baits. Currently, local applications of liquid termiticides are common practices because termite control professionals are often urged by homeowners to take remedial actions when termites are found in a house, but such treatments only drive termites away from the active loci without affecting the termite colony(s). Remedial treatments with fluid baits would result in immediate bait consumption and shorten colony elimination time with or without the use of in-ground baiting systems. Introduction of fluid baits will add another tool to the termite control industry and will make it more plausible for the homeowners to accept baiting technology.

Does Soil Treated with Conidial Formulations of Trichoderma spp. Attract or Repel Subterranean Termites?

Previous studies showed that many wood-rotting fungi were attractive to termites; however, little attention has been paid to the relationship between termites and soil fungus. In the present study, different designs of two-choice tests were conducted to investigate the behaviors of two subterranean termites, Coptotermes formosanus Shiraki (wood-feeding lower termites) and Odontotermes formosanus (Shiraki) (fungus-growing higher termites), in response to soil (or sand) treated with the commercial conidial formulations of Trichoderma harzianum Rifai (BioWorks) and Trichoderma viride Pers. ex Fries (Shuiguxin). The short-term (1 d) choice tests showed no significant difference in termite aggregation (C. formosanus and O. formosanus) between treated and untreated soil, regardless of Trichoderma species and concentrations. However, in the long-term choice tests, C. formosanus consumed significantly more wood in the chambers containing soil treated with the conidial formulation of T. viride (1 × 108 conidia/g) than that containing untreated soil. The tunneling choice tests showed that sand treated with T. viride (1 × 106 or 1 × 108 conidia/g) or T. harzianum (1 × 106 conidia/g) significantly increased the tunneling activities of C. formosanus. However, sand treated with T. viride (1 × 106 or 1 × 108 conidia/g) had a repellent effect on O. formosanus. Our study showed that the two subterranean termites behaved differently when responding to the conidial formulations of Trichoderma.

Escaping and repairing behaviors of the termite Odontotermes formosanus (Blattodea: Termitidae) in response to disturbance

The escaping behavior of termites has been documented under laboratory conditions; however, no study has been conducted in a field setting due to the difficulty of observing natural behaviors inside wood or structures (e.g., nests, tunnels, etc.). The black-winged termite, Odontotermes formosanus (Shiraki), is a subterranean macrotermitine species which builds extensive mud tubes on tree trunks. In the present study, 41 videos (totaling ∼2,700 min) were taken on 22 colonies/subcolonies of O. formosanus after their mud tubes were partially damaged by hand. In general, termites consistently demonstrated three phases of escape, including initiation (wandering near the mud-tube breach), individual escaping (single termites moving downward), and massive, unidirectional escaping flows (groups of termites moving downward). Downward moving and repairing were the dominant behavioral activities of individuals and were significantly more frequent than upward moving, turning/backward moving, or wandering. Interestingly, termites in escaping flows moved significantly faster than escaping individuals. Repairing behavior was observed shortly after the disturbance, and new mud tubes were preferentially constructed from the bottom up. When predators (i.e., ants) were present, however, termites stopped moving and quickly sealed the mud-tube openings by capping the broken ends. Our study provides an interesting example that documents an animal (besides humans) simultaneously carrying out pathway repairs and emergency evacuation without congestion.

Evaluation of fipronil and imidacloprid as bait active ingredients against fungus-growing termites (Blattodea: Termitidae: Macrotermitinae)

Fungus-growing termites (Macrotermitinae) are important pests in tropical countries. They are difficult to control with existing baiting methods, as chitin synthesis inhibitors are not effectual as active ingredients. We tested two neurotoxins, fipronil and imidacloprid, as potential bait active ingredients against Macrotermes gilvus (Hagen) in Singapore. In laboratory bioassays, M. gilvus showed no preference for doses of 0-64 ppm fipronil, or for doses of 0-250 ppm imidacloprid, indicating no repellence. We tested each insecticide in toilet paper as a bait matrix in a field experiment. After 28 days, termites had eaten 5-13% of the fipronil treated toilet paper, abandoned bait and monitoring stations, contacted no new stations, and repaired poorly their experimentally damaged mounds. Termites ate no imidacloprid treated toilet paper, abandoned bait stations although contacted new stations, and repaired fully their damaged mounds. Termites ate 60-70% of the control toilet paper, remained in bait stations, and fully repaired damaged mounds. After 56 days, all five fipronil colonies were eliminated, whereas all of the imidacloprid and control colonies were healthy. The results suggest that fipronil could be an effective active ingredient in bait systems for fungus-growing termites in tropical countries.

Molting site fidelity accounts for colony elimination of the Formosan subterranean termites (Isoptera: Rhinotermitidae) by chitin synthesis inhibitor baits

Site fidelity by molting termites in Formosan subterranean termite, Coptotermes formosanus Shiraki colonies is a new addition to our understanding of lower termites’ behavior and biology. Our previous studies indicated that workers moved to the central nest to molt in the presence of eggs and reproductives. The current study showed that noviflumuron-affected workers also return to the central nest and died in the vicinity of reproductives and eggs. The aversion to the dead and decaying workers caused reproductives and brood to leave the original central nest site in a colony and refuge at newer sites every few days in response to newly dead workers near them. Because mortality was an event observed only in workers undergoing molting under the effect of noviflumuron- a CSI, the death of molting individuals was observed only around reproductives and brood. This study reveals a previously undiscovered behavior of molting termites and the mechanics behind a successful arsenal; noviflumuron baits used against subterranean termites.

Sub-lethal effects of essential oil of Lippia sidoides on drywood termite Cryptotermes brevis (Blattodea: Termitoidea)

The drywood termite Cryptotermes brevis (Walker, 1853) (Kalotermitidae) is one of the most important wood structural pest in the world. Substances from the secondary metabolism of plants (e.g., essential oils) have been considered an environmentally safer form of control for urban pests, such as termites. In the present study, we analyzed the lethal and sub-lethal effects of essential oil of Lippia sidoides and its major components on C. brevis pseudergates in two routes of exposure (contact and fumigation). The essential oil of L. sidoides and thymol were more toxic to C. brevis pseudergates when applied by contact (LD₅₀ = 9.33 and 8.20µgmg^-1, respectively) and by fumigation (LC₅₀ = 9.10 and 23.6µLL^-1, respectively). In general, treatments changed the individual and collective behaviors of C. brevis pseudergates, as well as the displacement and walking speed. The essential oil of L. sidoides and its major components showed a high potential to control C. brevis pseudergates, due to the bioactivity in the two routes of exposure and the sub-lethal effects on the behavior and walking, important activities for the cohesion of C. brevis colonies.

Elimination of Coptotermes lacteus (Froggatt) (Blattodea: Rhinotemitidae) Colonies Using Bistrifluron Bait Applied through In-Ground Bait Stations Surrounding Mounds

The efficacy of bistrifluron termite bait was evaluated using in-ground bait stations placed around Coptotermes lacteus mounds in south-eastern Australia during late summer and autumn (late February to late May 2012). Four in-ground bait stations containing timber billets were placed around each of twenty mounds. Once sufficient numbers of in-ground stations were infested by termites, mounds were assigned to one of four groups (one, two, three or four 120 g bait canisters or 120 to 480 g bait in total per mound) and bait canisters installed. One mound, nominally assigned treatment with two canisters ultimately had no termite interception in any of the four in-ground stations and not treated. Eighteen of the remaining 19 colonies were eliminated by 12 weeks after bait placement, irrespective of bait quantity removed (range 43 to 480 g). Measures of colony decline-mound repair capability and internal core temperature-did not accurately reflect the colony decline, as untreated colonies showed a similar pattern of decline in both repair capability and internal mound core temperature. However, during the ensuing spring-summer period, capacity to repair the mound was restored in untreated colonies and the internal core temperature profile was similar to the previous spring-summer period which indicated that these untreated colonies remained healthy.

Hyperecdysonism in the Formosan Subterranean Termite and Eastern Subterranean Termite (Isoptera: Rhinotermitidae)

Effects of ecdysone, 20-hydroxyecdysone (20E), and an ecdysone agonist, halofenozide, were tested against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar), in a 12-d no choice assay. Approximately 22-26% of R. flavipes and C. formosanus exhibited symptoms of hyperecdysonism, that is, "jackknife" position, when exposed to ecdysone and 20E at 1,000 ppm, respectively. High mortalities were recorded for both termite species in ecdysone and 20E at 100 and 1,000 ppm, but only at 10,000 ppm for halofenizide. Termites are known to move back to the central nest before the onset of ecdysis, and those that ingested lethal doses of chitin synthesis inhibitors (CSIs) die near the royal pairs, which partially accounts for the success of CSI baits to eliminate subterranean termite colonies. Because ecdysteroids and their agonists induce molting in termites, incorporation of these compounds into baits could potentially achieve the same colony elimination. This study showed that lethal time (12 d) of ecdysteroids and ecdysone agonist is shorter than that of a CSI (45 d); hence, the baiting time should be reduced by more than a month when they are incorporated in termite baits.

Evaluation of Chlorfluazuron Against Subterranean Termites Heterotermes indicola (Isoptera: Rhinotermitidae) in Pakistan

Baiting systems have been introduced using slow-acting bait toxicants to provide environment-friendly and target-specific termite management. In the present study, the Exterra termite bait system (USA) with chlorfluazuron, a chitin synthesis inhibitor, as the active ingredient was tested against termite colonies. Ten residential areas of Lahore, infested with subterranean termites were selected for the study. The study period was from 2013 to 2015. In-ground stations were installed at 10 sites and above-ground stations were only installed at four test sites. Requiem termite bait was prepared according to the label instructions. Results showed that the range of termite activity was between 30 and 214 d to first termite activity on underground monitors with a mean of 78.23 ± 6.44. Timeline graphs also show activity of termites and active ingredient placement for each of the stations at each site. As termite feeding activity in the stations increased, there was a decrease in termite activities in wooden structures, followed by cessation of termite feeding and foraging activity noted in the building structures. It was concluded that a termite baiting system in Pakistan has the potential to suppress and reduce termite populations, when foraging termites feed on the active ingredient and share with nest mates through trophallaxis by installing more bait stations and prolonging baiting period.

Digestion of Termiticide Bait Matrices by the Pest Termite Reticulitermes flavipes (Isoptera: Rhinotermitidae)

Termites are highly effective digesters of wood lignocellulose, which is a central factor contributing to their global status as pests of wooden structures. For the same reason, termite baits that combine cellulosic matrices with slow-acting insecticides are both effective and popular as a reduced-risk approach for termite control. This study took a novel approach for assessing digestibility of termite bait matrices and matrix components to gain potentially new insights into bait attractiveness and efficacy. The rationale behind this study is that termite baits that are more digestible should have more nutritional value to termites and thus encourage maximal feeding and trophallactic transfer of active ingredients through termite colonies. Studies were done using in vitro digestion assays with termite gut protein extracts followed by colorimetric detection of released glucose and pentose monosaccharides from test substrates. The substrates tested included two commercial bait matrices (Recruit IV and Recruit II HD), two matrix components (compressed and toasted compressed cellulose), and two natural pine woods as positive controls (southern yellow and northern pine). Overall results show equal or greater monosaccharide availability for some commercial matrices than standard pine lignocelluloses, suggesting sufficient nutritional value for the proprietary matrices. Another more prominent trend was significant intercolony variation in digestibility across substrates, possibly resulting from differences in microbiota composition, long-term diet adaptation, or both. These findings thus illuminate new nutrition-based factors that can potentially impact bait feeding, trophallactic exchange, and efficacy.

Naturalization and Control of Coptotermes gestroi (Blattodea: Rhinotermitidae) in a Taiwanese Forest

Coptotermes gestroi (Wasmann), an invasive termite species in Taiwan, has been a major structural pest in southwestern Taiwan. C. gestroi was recently reported to have infested living trees in a Taiwanese forest, showing its potential of becoming an invasive forest pest in Taiwan. To determine whether C. gestroi have naturalized in the forests, we monitored their dispersal flights and estimated their colony development status on the basis of their worker and soldier morphology. The results showed that mature C. gestroi colonies occurred in forest, indicating that C. gestroi has naturalized. The colony sizes of C. gestroi were estimated using a triple mark-release-recapture method. The three studied colonies contained 0.12-0.20 million individuals, which was smaller than that reported in previous studies conducted in urban environments. We speculate that C. gestroi population is suppressed by ants and another dominant termite species, Odontotermes formosanus (Shiraki). Colony elimination was achieved four months after employing termite baits for controlling the three colonies of C. gestroi in forest. In summary, although C. gestroi have naturalized in Taiwan, their further expansion in the forest has likely been restricted by ants and other termite species. Termite baits can be a practical option for controlling C. gestroi in the forests.

Elimination of the Mound-Building Termite, Nasutitermes exitiosus (Isoptera: Termitidae) in South-Eastern Australia Using Bistrifluron Bait

Bistrifluron, a benzoylphenylurea compound, was evaluated for efficacy against Nasutitermes exitiosus (Hill), a mound-building species in southern Australia. Bistrifluron bait (trade name Xterm) was delivered as containerized pellets inserted into plastic feeding stations implanted in the sides of mounds-60 g for bistrifluron bait-treated mounds and 120 g of blank bait for untreated mounds. Termites actively tunneled in the gaps between pellets and removed bait from the canisters. All five treated mounds were eventually eliminated, and all five untreated mounds remained active at the end of the trial. Four of the five treated mounds were considered dead and excavated after 26 wk, but there were earlier signs of mound distress-reduced repair of experimental casement damage and reduced activity in bait canisters by 22 wk and reduced internal mound temperature after 11 wk. One treated mound showed activity in the bait station right through until almost the end of the trial (47 wk), but excavation at 49 wk showed no further activity in the mound. The five untreated colonies removed on average 97% of blank bait offered, while the five treated colonies removed on average 39.1% of bait offered. There was a wide variation in temperature profiles of mounds (up to 15°C for both minimum and maximum internal temperatures), from the beginning of the trial and even before the effects of baiting were evident.

Response of Microtermes mycophagus (Isoptera: Termitidae) to twenty one wood species

The responses of termite species to bait depend upon the quality of the food used in the stations. Woods are the most common food sources for termites but different termite species behave differently to different wood species and types. The knowledge of the preference status of different wood species to a termite species helps in effective monitoring and baiting program. The current study was carried out to evaluate the preference of 21 wood species to the termite, Microtermes mycophagus in the field by no-choice and choice feeding tests. The results indicated silk cotton tree and sacred fig woods as the most preferred wood species with mean mass losses of 71.21 ± 5.09% and 68.38 ± 7.27% in no-choice test and 95.02 ± 1.65% and 91.69 ± 2.07% in choice tests, respectively. White cedar was the least preferred wood species with mean mass losses of 7.49 ± 1.64% and 13.92 ± 1.89% in no choice and choice feeding tests, respectively. Based on present studies, sapwood of silk cotton tree and sacred fig may be used in effective monitoring and baiting program against M. mycophagus.