Biological control of Cimex lectularius with Beauveria bassiana: Effects of substrate, dosage, application strategy, and bed bug physiology.

BACKGROUND: Cimex lectularius L. (bed bug) (Hemiptera: Cimicidae) is a serious indoor pest worldwide, and this nuisance needs to be controlled using different methods in integrated pest management (IPM). Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) kills bed bugs, and insect pathogenic fungi may be utilized to control bed bugs in IPM. To increase knowledge of this methodology, forced exposure experiments were conducted with different formulations, doses, and substrates, using bed bugs in variable physiological states. RESULTS: Both oil- and water-formulated fungal products showed significant improvement when conidial concentrations were raised in five steps from 0.02 to 2.0%. At low concentrations (0.02% in water) effects from substrate and application strategy were observed. Application on soft substrates (cotton and polyester) yielded significantly higher bed bug mortality rates than on harder substrates (paper, wood, and linoleum) with a final mortality of 35-63% against 8-10%. Multiple applications over time also improved B. bassiana's ability to kill bed bugs, and at low concentrations only a triple application on cotton showed 100% final mortality. Bed bug age and reproductive status significantly affected survival. Older and reproducing individuals showed higher mortality compared to newly emerged adults. Differences in feeding status also yielded differences in mortality timing, but only minor differences in final mortality rates. Egg production and hatching success were significantly reduced by some treatments. CONCLUSION: B. bassiana appears to be an asset in the fight against bed bugs. Substrate, dosage, application strategy, and bed bug physiology are important factors to consider for optimal efficacy and safe indoor control with insect pathogenic fungi. © 2023 Society of Chemical Industry.

Procurement Competence and Framework Agreements for Upgraded Bed Bug Control [Cimex lectularius (Hemiptera: Cimicidae)].

The prevalence of bed bugs (Cimex lectularius L.) is increasing worldwide. Due to this increase, low-income housing owners and managers need an efficient method for controlling the pests without excessive resource use. The quality of pest control efforts is crucial for efficient eradication. Infestations often need to be approached using a variety of strategies through an integrated pest management (IPM) framework. Efficient eradication is often thought to be the responsibility of the pest control contractor alone. However, the purchase and supply management theory suggests that optimal solutions actually involve sound buyer-supplier relations to support the strategic aim of pest eradication. This study illustrates the positive outcomes of elevating pest management competence on the buyer's part. Further, this study outlines a large-scale purchase situation that quantifies bed bug control efforts, in addition to their outcomes. In total, 11,000 apartment units were observed in Oslo, Norway, over a period of six years. The release and implementation of a procurement officer together with a state-of-the-art pest management framework agreement quickly reversed the consistent escalation of bed bug infestations in the observed units. Observations revealed that the study yielded the most success in eradicating bed bugs by increasing both the number of visits to the infested apartment and the overall duration of control efforts. The improved control was achieved at a reduced cost per infested apartment unit, which allowed for the implementation of bed bug preventive measures and building-wide inspections. The observations made in this study have been discussed in the context of the impact of bed bugs in low-income communities, relative to the factors of pest burden, demography, socioeconomics, and the welfare system in Norway.

Spatiotemporal elements in a poisoned bait strategy against the long-tailed silverfish (Lepismatidae: Zygentoma).

The long-tailed silverfish Ctenolepisma longicaudatum (Lepismatidae: Zygentoma) is a nuisance problem in buildings and a major concern in museums, libraries and archives where it cause damage to historical and priceless items. We used laboratory bioassays and two field studies of infested buildings to evaluate spatial and temporal elements of a poisoned bait strategy. In both laboratory experiments and field studies, the efficiency of poisoned bait with indoxacarb as the active ingredient was significantly improved by placing many small bait droplets evenly distributed along all edges of the treated area compared to more clustered distributions. Extended duration of bait presence and removal of competing food sources improved the control effect significantly in the laboratory bioassays. Bait-treated populations also showed a significant decline in the number of eggs deposited and emergence of new nymphs. The study supports poisoned bait as an efficient and low risk approach against the long-tailed silverfish in which extended duration of bait presence, wide distribution of bait droplets in combination with sanitation was crucial for control in the infested premises.

Development of a Poisoned Bait Strategy against the Silverfish Ctenolepisma longicaudata (Escherich, 1905).

Pest management strives to be an efficient, yet healthy and environmentally safe control method, and the use of poisoned bait often fulfils these criteria. In the present study, we show that bait with indoxacarb as the active ingredient is highly efficient for controlling Ctenolepisma longicaudata (Escherich, 1905) and two of its relatives, Lepisma saccharina (Linnaeus, 1758) and Ctenolepisma calva (Ritter, 1910). Applying small bait droplets (size ~10 mg) along the walls of several types of buildings, at no more than 0.5 to 1.0 g bait per 100 m2, was a cost-efficient and safe strategy for the knockdown and eradication of C. longicaudata. During field experiments, the demography changed from an initial mixture of different stages to total dominance of early instars preceding the population collapse. Poisonous bait outcompeted mass-trapping with sticky-traps and conventional insect spray treatment for the efficient control of C. longicaudata in apartments. Different droplet densities (1 vs. 0.5/m2) and active ingredients (indoxacarb vs. clothianidin) did not have different effects in field experiments. These results show that poisoned bait is a highly relevant tool for managing C. longicaudata and potentially against other silverfish infestations.

Long-Tailed Silverfish (Ctenolepisma longicaudata) Control; Bait Choice Based on Primary and Secondary Poisoning.

The long-tailed silverfish (Ctenolepisma longicaudata) has recently made its appearance and demonstrated a tremendous proliferation in Norway, where it is currently considered a major indoor nuisance pest in modern buildings. To reduce the risk of human pesticide exposure, several baits with indoxacarb, clothianidin, fipronil or imidacloprid as the active ingredient were investigated to provide knowledge regarding their potential for integrated pest management solutions. Primary and secondary poisoning, as well as the durability of baits, were experimentally evaluated in bioassays. Baits with indoxacarb, clothianidin and fipronil killed more than 90% of the experimental insects (primary poisoning) when presented in competition with food. Only indoxacarb produced high mortality when dead conspecifics were consumed (secondary poisoning) and resulted in more than 75% mortality. The efficacy of baits with indoxacarb against C. longicaudata was also found to be very long. Laboratory degraded baits were consumed and induced high levels of mortality for more than a month, and field degraded baits for more than 6 months. Adults and juveniles were equally affected in the experiments. Primary and secondary toxicity in combination with long durability and effects on both life stages tested suggest that the bait has high-level potential as a safe control strategy against the long-tailed silverfish if indoxacarb is used as the active ingredient.

A Wind Tunnel for Odor Mediated Insect Behavioural Assays.

Olfaction is the most important sensory mechanism by which many insects interact with their environment and a wind tunnel is an excellent tool to study insect chemical ecology. Insects can locate point sources in a three-dimensional environment through the sensory interaction and sophisticated behavior. The quantification of this behavior is a key element in the development of new tools for pest control and decision support. A wind tunnel with a suitable flight section with laminar air flow, visual cues for in-flight feedback and a variety of options for the application of odors can be used to measure complex behaviour which subsequently may allow the identification of attractive or repellent odors, insect flight characteristics, visual-odor interactions and interactions between attractants and odors lingering as background odors in the environment. A wind tunnel holds the advantage of studying the odor mediated behavioural repertoire of an insect in a laboratory setting. Behavioural measures in a controlled setting provide the link between the insect physiology and field application. A wind tunnel must be a flexible tool and should easily support the changes to setup and hardware to fit different research questions. The major disadvantage to the wind tunnel setup described here, is the clean odor background which necessitates special attention when developing a synthetic volatile blend for field application.

Temperature stress deteriorates bed bug (Cimex lectularius) populations through decreased survival, fecundity and offspring success.

Sublethal heat stress may weaken bed bug infestations to potentially ease control. In the present study, experimental populations exposed to 34, 36 or 38°C for 2 or 3 weeks suffered significant mortality during exposure. Among survivors, egg production, egg hatching, moulting success and offspring proliferation decreased significantly in the subsequent 7 week recovery period at 22°C. The overall population success was negatively impacted by increasing temperature and duration of the stress. Such heat stress is inadequate as a single tool for eradication, but may be included as a low cost part of an integrated pest management protocol. Depending on the time available and infestation conditions, the success of some treatments can improve if sublethal heat is implemented prior to the onset of more conventional pest control measures.

Insect pathogenic fungi and bed bugs: behaviour, horizontal transfer and the potential contribution to IPM solutions.

The increasing problem of bed bugs requires the development of new control strategies, and insect pathogenic fungi can contribute towards management. We used laboratory bioassays with Isaria fumosoroseus, Lecanicillium muscarium and Beauveria bassiana to evaluate their virulence to the bed bug. Only B. bassiana significantly affected bed bug survival and was dependent on dose and formulation. A 2% B. bassiana oil formulation induced horizontal transfer to elevate mortality in a 10-day arena bioassay. Temporal distribution of contagious individuals and increasing the dose from 2 to 4% did not increase mortality. Horizontal transfer mainly occurred between adults, and only partly between adults and nymphs. Bed bugs showed activity peaks during the night, and activity was increased by elevated levels of CO2. Distribution between harbourages was not affected by CO2 activation, level of infection or the bio-pesticide, and horizontal transfer was not dependent on the degree of aggregation. Movement in the arenas negatively affected horizontal transfer when the number of susceptible individuals was large. Level of infection also influenced behaviour as the bed bug movement increased with elevated disease burden. The use of fungi as a part of an integrated pest management strategy seems to be an interesting option that should be investigated further. B. bassiana kills bed bugs and can be carried to harbourages to target hidden individuals.

Desiccant dust and the use of CO2 gas as a mobility stimulant for bed bugs: a potential control solution?

The common bed bug (Cimex lectularius, Hemiptera; Cimicidae) infests homes and service industries, and the number of infestations has greatly increased over the past 20 years. At present, no cost-effective control methods are available, and eradication programs are expensive and laborious. We investigated the control potential of desiccant dust in combination with CO2 as a bed bug activity stimulant. An initial experiment with two desiccant dusts was followed by arena studies with varying doses, available hiding places and the presence or absence of host signals. Finally, we conducted a field experiment with Syloid 244FP with or without CO2 gas. Syloid was superior compared to diatomaceous earth, and effective at the concentration of 1.0 g/m2 in the field experiment. The number of harborages and partial application of desiccant dust decreased mortality in the laboratory. Bed bug activation by CO2 appeared of minor importance in the arena studies, but was crucial for the eradication in the student dormitories. In fact, all 5 bed bug-infested dormitories with a combined treatment of desiccant dust and CO2 were freed of bed bugs, whereas eradication was not successful in any of the 6 dormitories with only desiccant dust treatment. The different results in the laboratory and field experiment were most likely caused by the longer activation and higher dose of CO2 used in the field experiment than the laboratory experiment. Our study showed that application of desiccant dust in combination with release of CO2 gas to mimic human presence is a promising option for bed bug control.

Mortality, fecundity and development among bed bugs (Cimex lectularius) exposed to prolonged, intermediate cold stress.

BACKGROUND: Bed bugs (Cimex lectularius L.) have returned as a nuisance pest worldwide. Their ability to withstand different types of environmental stress should be explored in order potentially to increase the efficiency of control methods. RESULTS: Immediate and long-term effects of exposure to temperatures from 0 to -10 °C for 1, 2 and 3 weeks are reported. Fifth-instar nymphs and adults were exposed to constant or fluctuating temperatures. Increased cold and extended time yielded higher mortality; nymphs were more resilient than adults at the shorter durations of exposure. At intermediate temperatures, mortality was higher at constant compared with fluctuating temperatures, whereas all individuals died after 3 weeks of exposure to -7 °C. The success among survivors after cold treatment was also affected in terms of reduced egg production, hatching success and the ability of fifth-instar nymphs to advance into the adult stage; however, nymphs produced after cold treatment developed normally. CONCLUSIONS: Detrimental effects of prolonged exposure to low temperatures were seen in bed bugs both during and after cold treatment. The results suggest that temperatures below -7 °C can be applied by laymen to control this pest in small items if available treatment time is of less concern. © 2016 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mortality, temporary sterilization, and maternal effects of sublethal heat in bed bugs.

Adult bed bugs were exposed to the sublethal temperatures 34.0°C, 35.5°C, 37.0°C, 38.5°C, or 40.0°C for 3, 6, or 9 days. The two uppermost temperatures induced 100% mortality within 9 and 2 days, respectively, whereas 34.0°C had no observable effect. The intermediate temperatures interacted with time to induce a limited level of mortality but had distinct effects on fecundity, reflected by decreases in the number of eggs produced and hatching success. Adult fecundity remained low for up to 40 days after heat exposure, and the time until fertility was restored correlated with the temperature-sum experienced during heat exposure. Three or 6 days of parental exposure to 38.5°C significantly lowered their offspring's feeding and moulting ability, which consequently led to a failure to continue beyond the third instar. Eggs that were deposited at 22.0°C before being exposed to 37.0°C for 3 or 6 days died, whereas eggs that were exposed to lower temperatures were not significantly affected. Eggs that were deposited during heat treatment exhibited high levels of mortality also at 34.0°C and 35.5°C. The observed negative effects of temperatures between 34.0°C and 40.0°C may be utilized in pest management, and sublethal temperature exposure ought to be further investigated as an additional tool to decimate or potentially eradicate bed bug populations. The effect of parental heat exposure on progeny demonstrates the importance of including maternal considerations when studying bed bug environmental stress reactions.

Questing activity in bed bug populations: male and female responses to host signals.

A large-arena bioassay is used to examine sex differences in spatiotemporal patterns of bed bug Cimex lectularius L. behavioural responses to either a human host or CO2 gas. After release in the centre of the arena, 90% of newly-fed bed bugs move to hiding places in the corners within 24 h. They require 3 days to settle down completely in the arena, with generally low activity levels and the absence of responses to human stimuli for 5 days. After 8-9 days, persistent responses can be recorded. Sex differences are observed, in which females are more active during establishment, respond faster after feeding, expose themselves more than males during the daytime, and respond more strongly to the host signal. The number of bed bugs that rest in harbourages is found to vary significantly according to light setting and sex. Both sexes stay inside harbourages more in daylight compared with night, and males hide more than females during the daytime but not during the night. The spatial distribution of the bed bugs is also found to change with the presence of CO2, and peak aggregation around the odour source is observed after 24 min. Both male and female bed bugs move from hiding places or the border of the arena toward the centre where CO2 is released. Peak responses are always highest during the night. Bed bug behaviour and behaviour-regulating features are discussed in the context of control methods.

Efficient mass trapping: catching the pest, Calliphora vicina, (Diptera, Calliphoridae), of Norwegian stockfish production.

Attracting high numbers of adult females, extensive trapping prior to damage, and a pest species with a predominantly univoltine lifecycle, are important factors contributing to the success of mass-trapping programs. We conducted a mass-trapping experiment over 4 years, using yellow sticky traps and odor-baited funnel traps for control of the blowfly Calliphora vicina in stockfish production areas in Loften, Norway. Blowfly-related damage to fish in five mass-trapping sites was compared with damage at five control sites. Population monitoring established a connection between blowfly activity and damage. Blowfly activity in the period from mid-April to mid-May was correlated with damage to fish in the same year. Interception (sticky) traps, based on visual cues, caught blowflies during the early drying period, whereas odor-baited funnel traps were more effective during the later drying period, and continued to catch flies throughout the year until late autumn. In the funnel traps, 80% of the captured flies were females. Compared to control sites, mass trapping reduced overall damage to stockfish by 8-31%. In the final year of the experiment, we compared mass-trapping and control treatments, controlling for drying time period and sun exposure (which both contribute to damage), and found a damage reduction of 63%. Thus, mass-trapping with a female-attracting kairomone, and using traps of different functionality to extend the critical trapping period, in accord with pest phenology, is an efficient method for control of C. vicina in stockfish production.