A Novel Strain of Steinernema riobrave (Rhabditida: Steinernematidae) Possesses Superior Virulence to Subterranean Termites (Isoptera: Rhinotermitidae)

Subterranean termites are major global pests of wood structures and wood products. Among the most economically important subterranean termite species in the US are Heterotermes aureus, Reticulitermes flavipes, and Coptotermes formosanus. In prior studies, the entomopathogenic nematode, Steinernema riobrave strain 355, exhibited a high level of virulence to H. aureus compared with other nematode species. However, S. riobrave 355 was reported to be poorly or only moderately virulent to R. flavipes and C. formosanus, respectively. We hypothesized that other strains of S. riobrave may possess a high level of virulence to all three termite species. Under laboratory conditions we compared three novel strains of S. riobrave (3-8b, 7-12, and TP) with the 355 strain for virulence to H. aureus, R. flavipes, and C. formosanus workers. H. aureus was very susceptible to all the S. riobrave strains, and termites in all nematode treatments were dead after 4 d. The TP strain of S. riobrave caused greater mortality in R. flavipes and C. formosanus compared to the other nematode strains. Specifically, the TP strain caused 75% and 91% mortality in R. flavipes and C. formosanus, respectively, which was more than 300% and 70% higher than the mortality caused by other strains. Additional studies are warranted to determine the ability of S. riobrave (TP) to control the targeted termite species under field conditions.     

Behavioral responses of two subterranean termite species (Isoptera: Rhinotermitidae) to instant freezing or chilling temperatures

The behavioral responses to instant freezing or chilling temperatures and survivorship of the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the Eastern subterranean termite, Reticulitermes flavipes (Kollar), were studied using a novel experimental design that closely simulated subterranean termites' natural in-ground environment. Both termite species responded to changes in temperature by exhibiting a downward mass movement from the cold to warmer area of constant temperature. However, the degrees of response were specific to the species and temperature regimen. Approximately 88 and 96% of R. flavipes escaped from instant 0 degrees C and chilling regimens (from 24 to 0 degrees C at a rate of 1 degrees C/h or 1 degrees C/12 h), respectively, compared with approximately 77 and 91% of C. formosanus. No significant difference was detected between the two cooling regimens in either termite species. Controls resulted in a relatively even distribution within test tubes in both termite species. The small portion of the termites that did not escape endured a cold coma at a 24-h 0 degrees C and had low mortality of 2.2 and <1% in R. flavipes and <5.2 and <3% in C. formosanus at instant and chilling regimens, respectively. This result may have implications for understanding group intelligence and decision making evolved by subterranean termites to survive temporary freezing cold.     

Responses of Coptotermes formosanus and Reticulitermes flavipes (Isoptera: Rhinotermitidae) to three types of wood rot fungi cultured on different substrates

This study examined the responses of two termite species, the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar), to three types of wood decay fungi: a brown rot fungus, Gloeophyllum trabeum (Persoon: Fries) Murrill; a white rot fungus, Phanerochaete chrysosporium Burdsall; and a litter rot fungus, Marasmiellus troyanus (Murrill) Singer. We also examined the responses of termites to these three types of fungi grown on different substrates. For all three fungal species, both termite species showed a strong preference for fungus-infected sawdust over uninfected sawdust. In choice tests, both termite species preferred sawdust infected with either M. troyanus or P. chrysosporium over G. trabeum. However, termites did not show any preference for fungus-infected potato dextrose agar over uninfected potato dextrose agar. Tunneling activity of C. formosanus was greater in sand treated with methanol extracts of fungus-infected sawdust than in sand treated with extracts of uninfected sawdust. Because chemicals in the fungal extracts caused termites to tunnel further into treated sand than untreated sand, these chemicals could potentially be used to direct termite foraging toward bait stations in the field.     

Tunneling and mortality of eastern and Formosan subterranean termites (Isoptera: Rhinotermitidae) in sand treated with thiamethoxam or fipronil

Thiamethoxam and fipronil were examined for their termiticidal properties against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar). Concentrations > or =8 ppm thiamethoxam and > or =1 ppm fipronil provided an effective barrier against C. formosanus and R. flavipes. Sand was penetrated to some degree at all concentrations of thiamethoxam (0-800 ppm for C. formosanus and 0-1000 ppm for R. flavipes) and fipronil (0-64 ppm for both C. formosanus and R. flavipes) tested, indicating that both termiticides are nonrepellent. Thiamethoxam was found to be more toxic against C. formosanus than R. flavipes whereas fipronil showed similar toxicity for both species. Higher mortality prevented termites from penetrating the entire 5-cm segment of treated sand.     

Ability of canine termite detectors to locate live termites and discriminate them from non-termite material

Dogs were trained to detect Eastern subterranean termites, Reticulitermes flavipes (Kollar), using the United States Customs method of scent detection dog training modified with a food reward. Dogs were tested with various numbers of Eastern subterranean termites placed in vented PVC containers. Trained dogs were 95.93% accurate in finding > or = 40 Eastern subterranean termite workers (positive indications) and incorrectly indicated the presence of termites in 2.69% of the containers without termites. Multiple species of termites [dark southern subterranean, R. virginicus (Banks); Formosan subterranean, Coptotermes formosanus Shiraki; powderpost, Cryptotermes cavifrons Banks; and southeastern drywood termites, Incisitermes snyderi (Light)], were similarly evaluated. Dogs trained to locate Eastern subterranean termites were also 100% accurate in finding dark southern subterranean termites, 98.89% accurate in finding Formosan subterranean termites, 97.33% accurate in finding powderpost termites, and 88.89% accurate in finding southeastern drywood termites. Dogs were able to discriminate live termites from non-termite material. Trained dogs' false response rate was 25.33% to Eastern subterranean termite-damaged wood, 6.67% to American cockroaches, Periplaneta americana (L.), and 2.67% to Florida carpenter ants, Camponotus floridanus Buckley.     

Toxicity of seven termiticides on the formosan and eastern subterranean termites

Using both topical application and substrate (sand) treatments the toxicities of seven new generation soil termiticides were evaluated to determine the LD50 and LC50 against two economically important subterranean termite species, eastern subterranean termite, Reticulitermes flavipes (Kollar), and Formosan subterranean termite, Coptotermes formosanus Shiraki. The lethal dose toxicity (LD50) rankings for R. flavipes from highest to lowest were: fipronil > bifenthrin > chlorantraniliprole > cyantraniliprole > imidacloprid > chlorfenapyr > indoxacarb; the rankings for C. formosanus were fipronil > imidacloprid > chlorantraniliprole > cyanthraniliprole> bifenthrin > chlorfenapyr > indoxacarb. The respective lethal concentration toxicity (LC50) rankings were fipronil > bifenthrin > chlorfenapyr > indoxacarb > cyantraniliprole > chlorantraniliprole > imidacloprid for R. flavipes; and fipronil > chlorfenapyr > bifenthrin >imidacloprid > cyantraniliprole > chlorantraniliprole > indoxacarb for C. formosanus. The study provides an opportunity to directly compare toxicity, action speed, and bioavailability among this group of newer generation soil termiticides.     

Time trends in mortality for thiamethoxam and fipronil against Formosan subterranean termites and eastern subterranean termites (Isoptera: Rhinotermitidae)

Time trends in mortality for the Formosan subterranean termite, Coptotermes formosanus Shiraki, and eastern subterranean termite, Reticulitermes flavipes (Kollar), were determined for thiamethoxam and fipronil. Filter paper treated with 50 ppm thiamethoxam led to >80% mortality in 2-4 d for R. flavipes, whereas 5 ppm thiamethoxam resulted in >80% mortality in 2-3 d for C. formosanus. Filter paper treated with 1 ppm fipronil resulted in >80% mortality in 5 d for R. flavipes and 9 d for C. formosanus, indicating that thiamethoxam is faster acting than fipronil. As concentration decreases for slow-acting termiticides, the time required for adverse effects to be fully expressed increases.     

Resistance of insecticide-treated foam board insulation against the eastern subterranean termite and the Formosan subterranean termite (Isoptera: Rhinotermitidae)

Three foam board types, one untreated control, one containing 2,000 ppm disodium octaborate tetrahydrate (DOT), and one containing 1,000 ppm deltamethrin, were exposed to field populations of the eastern subterranean termite, Reticulitermes flavipes (Kollar), and the Formosan subterranean termite, Coptotermes formosanus Shiraki. There was no significant difference in termite damage between foam boards treated with 2,000 ppm DOT and the untreated control. Form boards containing 1,000 ppm deltamethrin were not damaged by R. flavipes, whereas only minor damage occurred after exposure to C. formosanus.     

Tunneling activity of subterranean termites (Isoptera: Rhinotermitidae) in sand with moisture gradients

Tunnel formation by Coptotermes formosanus and Reticulitermes flavipes was studied in a two-dimensional foraging arena with a moisture gradient. Moisture did not appear to affect tunneling when termite first emerged from the central release chamber. But as termites of both species moved further away from the chamber and into a moisture gradient, they tunneled significantly (P < 0.05) more in sand with a higher moisture content than in sand with a lower moisture content. Over the 10 d test period, both termite species tunneled more in sand with a higher moisture content. Fractal analysis indicated that regardless of the sand moisture content, termite tunnel geometry had a fractal dimension and termites generally tunneled more in higher moisture sand.     

Prospects for the biological control of subterranean termites (Isoptera: rhinotermitidae), with special reference to Coptotermes formosanus

Costs associated with subterranean termite damage and control are estimated to approach $2 billion annually in the United States alone. The Formosan subterranean termite, Coptotermes formosanus Shiraki, is one of the more economically important subterranean species. In recent years, the shortcomings associated with conventional chemical control methods have prompted policymakers and scientists to evaluate the potential for biological control of subterranean termites (C. formosanus in particular), that is, to determine the potential for natural enemies - predators, parasitoids and pathogens - to suppress termite populations. Ants are the greatest predators of termites, and may have a considerable local impact on termite populations in some areas of the world. A few parasitoids of termites are known, but their potential for regulating termite populations seems negligible. Characteristics of the colony, such as a protected, underground location (and, for the C. formosanus nest, its modular and dispersed nature), are likely to limit the impact predators and parasitoids have on subterranean termites. Thus, there seems little potential for use of these agents for subterranean termite control. For various reasons, pathogenic organisms, such as viruses, bacteria, Protozoa, nematodes and most fungi, have shown little promise for use in biological termite control. However, research suggests that strains of two well-studied, endoparasitic fungi, Beauveria bassiana and Metarhizium anisopliae, when employed in baiting schemes, may offer the potential for at least some measure of subterranean termite control, although their successful use is compromised by a number of inherent biological limitations and logistical problems that have yet to be solved. Although not strictly in the realm of classical biological control, recent studies suggest that natural products, such as ant semiochemicals and fungal metabolites (siderophores), or their synthetic analogues, eventually might find a use in termite control programmes as repellents or insecticides in wood treatments or soil applications if stable formulations can be developed.     

Influence of soil compaction on tunnel network construction by the eastern subterranean termite (Isoptera: Rhinotermitidae)

Eastern subterranean termites, Reticulitermes flavipes (Kollar), workers were introduced into arenas containing low, moderate, and high compaction builder's sand (1.05 g/cm3, 1.18 g/cm3 or 1.35 g/cm3 bulk densities, respectively), and they immediately began tunneling. Termites built the tunnel network significantly fastest in soil of low compaction compared with moderately or highly compacted soil. In soil of low compaction, 221.67 +/- 4.73 cm of total tunnel distance was constructed in 1 d compared with only 96 cm of tunneling in highly compacted soil. At 14 d, total tunnel distance averaged 216.83 +/- 4.56 cm in soil of low compaction compared with 169.70 +/- 4.10 and 181.18 +/- 6.13 cm in moderately and highly compacted soil, respectively. Decreases in total tunnel distance between 1 and 14 d were caused by backfilling of seldom-used tunnels. Termites did the majority of tunneling during the first day of introduction into arenas. In soil of low and moderate compaction, termites essentially constructed the entire tunnel network within the first day, only modifying it by backfilling or maintaining tunnels. In highly compacted soil, 53% of the final tunnel network was constructed during the first day, 87% was constructed by the third day, and 97% was constructed by the seventh day. Soil compaction did not affect the number of primary tunnels or the number and diameter of secondary tunnels. The angle between the secondary tunnel and primary tunnel also was not significantly affected by soil compaction. However, the number of secondary tunnels in soil of low compaction (5.89 +/- 0.51) was significantly greater than in moderately (2.74 +/- 0.36) and highly (3.58 +/- 0.59) compacted soils.     

Behavioral Response of Two Subterranean Termites (Isoptera: Rhinotermitidae) to Vibrational Stimuli

Behavioral responses to vibrational stimuli were examined in two subterranean termite species, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar). Termites habituated to vibrational stimulation when in social groups, but failed to do so individually, indicating that habituation is a collective action. In assays on termite groups, both species demonstrated a similar pattern of behavioral responses to vibrational stimuli: evanescent cessation of activity and movement, followed by withdrawal from the vibration source. Groups of both species then gradually moved back toward the vibration source as a consequence of continuous exposure. However, it took a significantly shorter period for C. formosanus to return (57 s) to the test arena and to resume (80 s) normal foraging activities in the test arena compared with R. flavipes, which took 97 and 227 s, respectively, when exposed to the vibration frequency of 120 bmpm. High vibration frequency (240 bmpm) increased the time required to return (C. formosanus, 80 s; R. flavipes, 153 s) and to resume regular locomotion (C. formosanus, 186 s; R. flavipes, 263 s). Our experiments demonstrate that workers play a crucial part in adjusting groups of termites to distressful vibrations. Soldiers of R. flavipes demonstrated similar behavioral responses as workers, however, C. formosanus soldiers exhibited a transient positive response before withdrawal. An erratum to this article is available at .     

Valuation of efficacy and nonrepellency of indoxacarb and fipronil-treated soil at various concentrations and thicknesses against two subterranean termites (Isoptera: Rhinotermitidae)

The efficacy and nonrepellency of indoxacarb (150 SC, 150 g [AI]/liter) and fipronil (Termidor SC, 9.1% [Al]) against field-collected eastern subterranean termite, Reticulitermes flavipes (Kollar), and the Formosan subterranean termite, Coptotermes formosanus Shiraki, were evaluated for mortality and penetration into treated soil in laboratory glass tube bioassays. Both insecticides were tested at five concentrations (0, 1, 10, 50, and 100 ppm) and two thicknesses (20 and 50 mm) of treated soil. Indoxacarb caused significantly greater mortality than controls at all treatment thicknesses of > or = 10 ppm, but not at 1 ppm. Concentration and treatment thickness of indoxacarb significantly affected termite mortality. Eastern subterranean termites were significantly more susceptible to indoxacarb than Formosan subterranean termites, but there were no intercolony differences in either species. Termites completely penetrated through all treatment thickness of indoxacarb-treated soil at all concentrations, except one of the six Formosan subterranean termite replicates of 50 mm at 50 ppm, when all termites were killed before tunneling through the treated soil. Fipronil resulted in significantly faster and greater termite mortality than indoxacarb at corresponding concentrations. Concentration and treatment thickness of fipronil also significantly affected termite mortality. There was no intercolony difference in susceptibility to either insecticide in either termite. Both termite species completely penetrated 20-mm treatments of all tested fipronil concentrations, as well as 50-mm soil treated with fipronil at < or = 10 ppm. At 50 and 100 ppm fipronil, termites tunneled only a mean of 87 +/- 0.21 and 47 +/- 0.18% deep into 50-mm treated soil, respectively, before death. Both insecticides demonstrated a delayed mode of activity and nonrepellency against the two termite species.     

Laboratory assays evaluate the influence of physical guidelines on subterranean termite (Isoptera: Rhinotermitidae) tunneling, bait discovery, and consumption

Laboratory assays were conducted to determine whether physical guidelines could direct subterranean termite foraging behavior. Several materials (wood, plastics, and wood thermoplastic composites) were evaluated for their potential to serve as termite guidelines. Termite tunneling along the different types of guidelines was measured. The proportion of baits discovered when connected by a guideline was compared with the proportion of unconnected baits discovered. Termite consumption of baits also was quantified. Assay results indicated that the termites did not respond to all guideline materials in the same way. Termites built significantly longer tunnels along wood guidelines than they did along any of the plastic guidelines tested. However, tunnel length along the wood and the wood thermoplastic composites was not significantly different. The probability of two baits being discovered when they were connected by wood guidelines was significantly greater than when the baits were connected by plastic guidelines or left unconnected (no guideline). Pairs of baits connected by wood thermoplastic composites were also significantly more likely to be discovered than unconnected baits. Bait consumption was not enhanced by the presence of the guidelines. It is likely that guidelines made of wood competed with the baits as a termite food resource.     

Food encounter rates of simulated termite tunnels with variable food size/distribution pattern and tunnel branch length

Subterranean termites excavate tunnels in a search pattern to encounter food in soil. To investigate the effect of food size, food distribution and the branch length of tunnels on food encounter rate we used a lattice gas model to simulate tunnels of the Formosan subterranean termite, Coptotermes formosanus Shiraki. The model made use of minimized local rules derived from empirical data to simulate termite tunnel patterns in featureless soil. Food distributions with three types (uniform, random, and clumped) were defined by using an I-index proposed by Zimmer and Johnson (1985). The food encounter rate was higher in a clumped than in non-clumped (uniform and random) distribution of food particles. When food particle size was varied in random distributions of food particles a maximum encounter rate was found, with particles of larger or smaller size being encountered less frequently. We also discussed the relationship between the branch tunnel length and the tunnel search pattern in minimizing the redundancy of overlapping branches.     

Elimination and reinvasion studies with Coptotermes formosanus (Isoptera: Rhinotermitidae) in Louisiana

Three Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), colonies located inside the 12.75-ha Louis Armstrong Park, New Orleans, were selected for elimination by using the chitin synthesis inhibitor hexaflumuron. Once eliminated, each vacated foraging territory was monitored for reinvasion by neighboring C. formosanus colonies, Reticulitermnes flavipes (Kollar) (Isoptera: Rhinotermitidae) colonies, or both. Each selected colony was eliminated in approximately 3 mo by using baits containing hexaflumuron. Overall activity of each untreated colony in the park remained unchanged during the same period. New C. formosanus and R. flavipes activity was detected in two of the three vacated territories, and in both areas, within days of selected colony elimination. The third vacated territory was completely reoccupied by a new C. formosanus colony approximately 7 mo later. Mark-recapture studies and DNA fingerprinting confirmed the distinctness of the reinvaders from eliminated and neighboring colonies.     

In situ morphology of the gut microbiota of wood-eating termites [Reticulitermes flavipes (Kollar) and Coptotermes formosanus Shiraki].

Light microscopy and scanning and transmission electron microscopy were used to examine the in situ morphology of the gut microbiota of Reticulitermes flavipes and Caoptotermes formosanus. Laboratory-maintained termites were used and, for R. flavipes, specimens were also prepared immediately after collection from a natural infestation. The latter endeavor enabled a study of different castes and developmental stages of R. flavipes and revealed differences in the microbiota of field versus laboratory specimens. The termite paunch microbiota consisted of an abundance of morphologically diverse bacteria and protozoa. Thirteen bacterial morphotypes in the paunch were described in detail: seven were observed only in R. flavipes, three were observed only in C. formosanus, and three were common to both termite species. The paunch epithelium was densely colonized by bacteria, many of which possessed holdfast elements that secured them tightly to this tissue and to other bacterial cells. Besides bacteria, the protozoan Pyrsonympha vertens adhered to the paunch epithelium of R. flavipes by means of an attachment organelle. Cuplike indentations were present on the paunch epithelial surface and were sites of bacterial aggregation. Ultrastructural features of cups suggested their involvement in ion absorption. In addition to the paunch, the midgut was also colonized by bacteria that were situated between epithelial microvilli. Results suggest that bacteria are an integral part of the gut ecosystem.     

Population density, species abundance, and breeding structure of subterranean termite colonies in and around infested houses in central North Carolina

Pressure from subterranean termites is known to vary geographically across the United States, but there are few quantitative studies concerning the threat of structural infestation for any geographic region. We assessed the number and locations of termite colonies present on 20 infested residential properties in central North Carolina, where subterranean termite pressure is considered to be heavy. This was achieved by using microsatellite markers to determine colony identity of termites collected over 6-14 mo from mud tubes in structures, below-ground monitors, and wood debris in the yard. In total, we identified 188 distinct colonies and determined their breeding structures. Reticulitermes flavipes (Kollar) was by far the most common species, accounting for nearly 90% of all colonies; the remaining colonies belonged to Reticulitermes hageni Banks and Reticulitermes virginicus (Banks). In four cases, there were two colonies infesting a structure simultaneously; in all other cases only a single colony was detected in the structure. Colony densities were high, averaging 62 colonies per ha (25 per acre) with a maximum of 185 colonies per ha (75 colonies per acre). Foraging ranges of R. flavipes and R. hageni colonies were generally small (<30 linear m), and most colonies were headed by a single pair of monogamous reproductives with nearly all the remaining colonies headed by relatively few inbreeding descendants of the original monogamous pair. These results provide the most detailed picture to date of the number, distribution, and colony characteristics of subterranean termite colonies located in and around residential structures.     

Effects of concentration,distance, and application methods of Altriset (Chlorantraniliprole) on eastern subterranean termite (Isoptera: Rhinotermitidae)

The effects of various concentrations, distance, and application methods of Altriset (Chlorantraniliprole) were investigated against one of the most destructive termites, the eastern subterranean termite, Reticulitermes flavipes Kollar. Three laboratory experiments were conducted. First, we examined the concentration effect of treating the soil contiguously to established foraging tunnels at a fixed 1 m distance. The results demonstrated 100% termite control in 19 d posttreatment at 100 and 50 μg/g and 27% termite mortality at 25 μg/g. Second, we tested the distance effect of the soil treatment (2 and 4 m) on the efficacy of Altriset to the satellite termite populations at a fixed 50 μg/g concentration. This resulted in 100% termite control in 22 d posttreatment at both 2 and 4 m. Third, we examined the effect of differing application methods using 12.5 and 25 μg/g prior to the establishment of foraging tunnels at a fixed 1m distance. This illustrated 100% termite control in 9 d posttreatment at 25 μg/g and 12 d posttreatment at 12.5 μg/g. The third experiment demonstrated soil treatments that were applied prior to termite tunnel establishment had greater efficacy than applications made post tunnel construction. Our results provide a comprehensive understanding about the efficacy of Altriset treatments on eastern subterranean termites.     

Laboratory performance and pharmacokinetics of the benzoylphenylurea noviflumuron in eastern subterranean termites (Isoptera: Rhinotermitidae)

A benzoylphenylurea insect growth regulator with the common name noviflumuron was evaluated for use as a baiting toxicant against the eastern subterranean termite, Reticulitermes flavipes (Kollar). Noviflumuron demonstrated significantly greater potency and faster speed of action compared with the commercial standard hexaflumuron. In addition, noviflumuron was not a feeding deterrent on filter paper at concentrations of up to 10,000 ppm. The rates of uptake, clearance, and insect-to-insect transfer of [14C] noviflumuron were measured in R. flavipes in laboratory assays and compared with those previously reported for [14C]hexaflumuron. Under a continuous exposure regime, the uptake profile for noviflumuron was similar to that for hexaflumuron, although the time period of maximal uptake was shorter for noviflumuron. Noviflumuron was cleared from termites in a first order process with a half-life of approximately 29 d, whereas the half-life of hexaflumuron was much shorter (8-9 d). Noviflumuron was efficiently transferred from treated to untreated termites by trophallaxis via kinetics similar to those reported for hexaflumuron; however, the systemic dose of noviflumuron required to result in toxicity of R. flavipes was found to be at least two- to three-fold less than that of hexaflumuron. The faster activity of noviflumuron compared with hexaflumuron in R. flavipes can be at least partially explained by the combination of slower clearance and greater intrinsic activity.