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Laboratory Evaluation of Two Chitin Synthesis Inhibitors, Hexaflumuron and Diflubenzuron, as Bait Toxicants Against Formosan and Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

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Abstract

Two chitin synthesis inhibitors, hexaflumuron and diflubenzuron, were evaluated in a laboratory choice test for their potential as bait toxicants against the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the eastern subterranean termite, Reticulitermes flavipes (Kollar).Concentrations of hexaflumuron that elicited feeding deterrence were >125 ppm for C. formosanus and >62.5 ppm for R. flavipes, whereas concentrations required to cause >90% mortality at 9 wk were > 15.6 ppm and >2 ppm for C. formosanus and R. flavipes, respectively. Diflubenzuron deterred feeding of C. formosanus at such low concentrations (>2 ppm) that the highest recorded mortality was only 50% and is not likely to be effective in a bait against this termite species. More than 80% of R. flavipes workers died after feeding on diflubenzuron at >7.8 ppm, whereas feeding deterrence was recorded at >31.3 ppm. We conclude that hexaflumuron is superior to diflubenzuron as a bait toxicant because it is effective over a concentration range of 15.6-62.5 ppm. This concentration range is lethal and nondeterrent for both C. formosanus and R. flavipes. Diflubenzuron is efficacious against R. flavipes over a fairly narrow range of concentrations (7.8-31.3 ppm) and does not appear to be useful as a bait toxicant against C. formosanus.
... It is likely that only a portion of a colony's workers can actively forage at any given time (Du et al. 2017;Su et al. 2017;Yang et al. 2009). The number of active foragers may vary by species and colony size and may even differ among CSI formulations (Gautam and Henderson 2014;Lewis and Forschler 2017;Osbrink et al. 2011;Su and Scheffrahn 1993;Sukartana et al. 2009;Vahabzadeh et al. 2007). Formulations and label directions of most current commercial CSI termite bait products are designed to result in the highest possible number of termites feeding on the highest possible amount of bait to ensure colony elimination, regardless of the conditions, including the existence of multiple subterranean termite colonies around a treated structure. ...
... Determining the minimal amount of CSI bait required to eliminate a single termite colony in the field remains challenging because the size, health, and territory of field colonies are often unknown. As a result, many experiments involving CSIs have used relatively small groups of termites in the laboratory (Gautam and Henderson 2014;Kubota et al. 2006;Lewis and Forschler 2017;Su and Scheffrahn 1993). These experiments were unable to account for the complexity of large/entire colonies Su 2014, 2017), and their results may therefore not reflect the efficacy and bait transfer that occurs at a larger scale. ...
... Numerous studies have demonstrated the efficacy of CSI baits against both Coptotermes formosanus Shiraki and C. gestroi colonies (Chouvenc 2018;Chouvenc and Su 2017;Evans et al. 2013;Grace et al. 1996;Kakkar et al. 2018;Osbrink et al. 2011;Su 1994;Su and Scheffrahn 1993). Multi-resource feeding (Grace and Su 2001) and a unique radially branching foraging pattern (Campora and Grace 2001;Puche and Su 2001) may increase the likelihood of a bait being "hit" by C. formosanus foragers (Campora and Grace 2001;Grace and Su 2001;Puche and Su 2001). ...
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Termite bait products that contain chitin synthesis inhibitors (CSIs) protect structures from subterranean termites via colony elimination. A hallmark of CSI baits is their dose-independent lethal time, as workers exposed to a CSI do not die until they initiate the molting process. Due to this mode of action and termite behaviors such as trophallaxis and cannibalism, a relatively small quantity of ingested CSI can spread throughout an entire colony before secondary repellency or avoidance behaviors occur, ultimately resulting in total colony elimination. In the field, only a portion of a subterranean termite colony actively forages upon a CSI bait at any given time, suggesting that only a relatively small proportion of workers may need to feed upon a CSI bait for a colony to be eliminated. In the present study, we used varying proportions of workers from whole four-year-old laboratory-reared Coptotermes gestroi (Wasmann) colonies (~ 62,500 termites/colony on average) to determine what proportion of workers need to feed upon a CSI bait in order to achieve colony elimination. A range of 0% (control), 0.5%, 1%, 2.5%, and 5% of the total worker population of colonies was allowed to feed on a formulated 0.5% noviflumuron bait for five days before being returned to their colonies. Colony elimination was observed for all 5%-fed and four out of six 2.5%-fed colonies by 107 days after CSI exposure. Our results confirm that only a small subset of the worker population of a colony must feed upon a CSI bait to achieve subterranean termite colony elimination.
... The methodology is based on use of a termite baiting system. After laboratory and field research studies [3], [4], [5], baits became commercially available in 1995 on USA market (SentriconTM). The baits utilized in this experiment contained 0.5 % (w/w) hexaflumuron (HEX), which is an insect growth regulator (IGR), and another insecticide, benzoilurea. ...
... Further, due to the importance of the site the utilization of a method of eradication that could permit the usability of site during the treatment without any health risk for monks and visitors of this site. This methodology based on baits, after the laboratory and in field research steps, [3], [4], [5], become commercially available in 1995 in USA market (SEN-TRITM). The baits utilized in this experiment contained 0.5 % (w/w) of Hexaflumuron and another insecticide, benzoylurea, that is an Insect Growth Regulator (IGR). ...
... One group of insect growth regulators, the chitin synthesis inhibitors (CSIs), have proven effective as active ingredients (AIs) in baiting systems [4][5][6]. Subterranean termite colonies consuming CSI bait formulations are eliminated, providing area-wide structural protection for extended periods of time [2,3,[7][8][9]. Successful termite baiting systems were only made possible by CSI's unique characteristics. ...
... For an AI to serve as an effective toxicant in a bait, termites cannot be deterred from ingesting it at lethal concentrations [21]. If a given species of termite is deterred from feeding on an AI at a concentration that is lower than the required concentration to cause mortality, then the compound will not be effective as a bait toxicant because termites cannot be force-fed in the field [5]. For example, hexaflumuron was shown to be a much better AI for use in baiting than lufenuron, because deterrence was not observed until 8000 and 4000 ppm for C. formosanus and R. flavipes, respectively [12]. ...
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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.
... The foraging termite workers feed on the biocide-impregnated bait, go back to their nests and feed their nest mates by trophallaxis. The CSI affects the molt into the next stage and thus kills the whole termite state (Su and Scheffrahn, 1993). ...
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At the end of April 2018, a pest control company brought three termite soldiers and some alates to the Urban Pest Advisory Service (UPAS) for species determination. They were found in a building in a medium-sized city on Lake Zurich (Canton Zurich). A mitochondrial DNA analysis by the University of Bologna, Italy, resulted in the species Reticulitermes grassei Clément. R. grassei is native on the Iberian Peninsula and in the southwest of France, whereas subterranean termites are not native in Switzerland. In June 2019, 24 termite bait stations were installed on the site of the infested house and three adjacent properties. One month later the first inspection showed termite activity in two bait stations of one of the adjacent properties. The approach and the challenges in the survey of infested area, the control methods, and the legal situation in Switzerland are presented.
... Kubota et al., (2006) reported that Bistrifluron demonstrates a speedier action rate against C. formosanus than hexaflumuron. Su and Scheffrahn,(1993) observed that hexaflumuron is a bait toxicant against both Reticulitermes flavipes and Coptotermes formosanus. The anti-termite activity of these toxicants is increasing because their chemical structure also increases the number of fluorine molecules. ...
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For increased crop production, the role of chemical termiticides cannot be neglected as they have provided the efficient way to achieve green revolution. But the present scenario has forced mankind to search for alternative options. While keeping in mind the concept of sustainable agriculture, pest management including termites and other phyto-diseases etc. needs to be focused. For the achievement of the above stated goal, eco-friendly and cost-effective strategies need to be emphasized. Biopesticidal agents that mainly comprise of herbal and microbial formulations are known to exhibit anti termite activity and have a pivotal role in the production of organic food products. In order to reduce the chemical consumption, the vast area of biological alternatives needs to be explored as they provide us with many beneficial aspects like sustainability, suitable application, biodegradable nature, target specificity etc. Further, the bioactive components of such biological agents can later be used as commercially viable termiticides in the form of formulations. These herbal and microbial termiticides are effective and have immense scope to be used in future for sustainable development.
... Inactivity of roughly 70% of the colonies in the treatment site occurred within 4-8 weeks after baiting. The time to elimination is dependent on how soon a colony starts to feed on the CSI baits [58,59], and as these colonies were active in the stations at the time novaluron was introduced, it is presumed that feeding started immediately. Decreased time to colony elimination has also been shown in other baiting systems that induce immediate feeding (i.e. ...
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Simple Summary: Subterranean termites cause damage to man-made structures around the world and are continuing to invade new areas. Current practices for controlling termites generally target a single colony as workers tunnel near these structures, and although they are effective in most instances, they never reduce the overall termite pressure in the surrounding area. An area-wide approach to pest management could offer a way of controlling termites at the population level. By eliminating all or most of the colonies within a given area, the threat of infestation decreases. We tracked individual termite colonies over time, before and after the introduction of termite baits, to assess how long these colonies remained active to determine if a termite-free area could be maintained with continued baiting. This baiting approach was successful in significantly reducing the overall termite population within a baited area. Abstract: 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 Re-ticulitermes flavipes, as well as evidence that an area-wide baiting program is feasible to maintain a termite-free area within its native range.
Chapter
Wood is an essential renewable resource which has been utilized in most of the sectors like housing, construction, furniture making, etc. Due to the immense damage caused by the wood degrading agents, there is a surge in demand to protect wood and its products. Wood preservation is an impeccable step to elude the degrading agents. It prolongs the service life of wood and its products. Numerous treatment methodologies have been inculcated for applying the preservatives in wood. As a result, the treated wood improves resistance against the agents of degradation. The preservatives used should be economical and less hazardous to living beings and environment. The main objective of this chapter is to convey to researchers about the recent developments on chemical preservative formulations which have an immense efficiency in enhancing the service life of wood and its products than the ones used earlier.KeywordsWood preservationChemical preservativesWood degrading agentsService life
Article
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.
Chapter
Termites are eusocial insects belonging to the insect infraorder Isoptera and are characterized by their colonial behavior. The word Isoptera originated from the Greek words isos which means equal and pteron which means wing and refers to the two pairs of identical wings in the adult. Termites are polymorphic insects, living in large communities of several hundred to several million individuals, composed of alate or apterous reproductive forms together with numerous apterous sterile soldiers and workers. Their numerous colonies have great influence in many ecosystems. There are 12 families of which the family Termitidae is the largest accounting about 75 percent of all termites. With the peculiar digestive system and the ability to digest lignocelluloses, the most abundant resource on the planet, termites became the most successful insects. Termites built huge and most complex nesting systems ever known by an insect. They change the ecosystems by their activities, and at the same time, they are dreaded pests on agriculture and man-made wooden structures. Due to their cryptic life, it is very difficult to manage them. Though chemical insecticides are very effective on termites, their method of application is challenging. Killing few thousand termite workers does not mean killing the colony; as long as the primary and secondary reproductives are alive and active deep inside the termite mounds, the termite problem exists, perennially.
Preprint
The research is based on the inspection performed in June 2002 for carrying out a research program for the eradication of a termite infestation due a desertic species in the area of the Saint Catherine Holy Monastery at Mount Sinai - Egypt. The paper describes the application of the registered European bait system SentritechTM and the trend of eradication during the first year. The application of bait system blocked the termite infestation inside the Katholikon (Main church) and in the surrounding after 6 months. Nevertheless, the infestation restarted and even increased again in the surrounding of the main church. An explanation of this surprising event is attempted in this paper.
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