Evaluation of Alternative Control Methods for Eliminating Insecticide-Resistant Bed Bugs (Cimex lectularius L.)
Todd, Dakotah Brooks
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The common bed bug, Cimex lectularius L, has been a persistent pest of humans. Conventional pyrethroid-formulation insecticides are known to be ineffective for controlling modern bed bug populations. This study evaluates alternative treatment methods such as whole-home heat, a biological control agent (Beauveria bassiana), and the fumigant sulfuryl fluoride for control of insecticide-resistant bed bugs. Three heat systems with different energy sources (propane, electric, and glycol) were evaluated to determine attributes contributing to heat treatment efficacy. The glycol system produced the most mortality of the three systems, killing all nymphs, eggs, and most adults. Heat treatment duration and achieving lethal temperatures in complex environments were found to be the most important factors for treatment efficacy. These factors were directly correlated with technician diligence, specifically regarding monitoring surface temperatures and repositioning equipment. A formulation of B. bassiana was evaluated in the laboratory to determine its ability to infect bed bugs under varying conditions of temperature (15°C, 21°C, and 32°C) and humidity (30%, 50%, and 70%). It was found that humidity conditions (30%-50%) at ≈21°C produced the greatest bed bug mortality and the shortest bed bug median survival time. The fumigant sulfuryl fluoride was evaluated for its ability to eliminate bed bugs from motor vehicles and cargo trailers filled to 85% capacity. This study was the first to document that sulfuryl fluoride fumigation at the 1.9X dosage factor can kill all pyrethroid-resistant bed bug life stages (including eggs) in motor vehicles as well as in chambers filled with personal items.
General Audience Abstract
Since the world-wide bed bug (Cimex lectularius L.) resurgence began in the late 1990s, populations of the common bed bug have been evaluated, but most have been found to be highly resistant to pyrethroid insecticides. This resistance has been particularly troublesome due to the fact that the 1996 US Food Quality Protection Act has eliminated the use of many existing chemistries from indoor use and has inadvertently limited the development of new active ingredients for indoor use due to the cost of the required animal testing to document the No Observable Effects Level (NOEL). Due to the lack of novel chemistry for addressing modern bed bug infestations, pest management professionals have had to identify new methods for applying existing products (chemical and non-chemical) for bed bug control. This study evaluated gaseous, mechanical, and biological control methods for bed bug elimination to determine which factors contribute the most to their efficacy, as well as how these methods might be applied in novel ways for control of bed bugs in homes, personal belongings, and even vehicles. At the turn of the 20th century heat treatments were used for controlling bed bug infestations in homes and other structures. Today, mechanical heating systems are again being used to control bed bug infestations in homes and apartments. This study investigated the utility of three commercial heating systems for their ability to control existing infestations in apartment units. The three heat systems utilized different energy sources, different types of delivery equipment, and required different set up and take down procedures in apartments of different cubic footage and clutter levels. Overall, the Assault glycol heating system was found to be the most effective in its ability to get (almost) all of our hidden (in hard to heat locations) temperature sensors up to bed bug lethal temperature. Interestingly, our statistical analysis determined that getting the hard to heat locations up to lethal temperature was directly correlated with heat technician activity. The more times that the technician entered the home to monitor the treatment and adjust the equipment positions, the greater the chance of getting the hidden sensors up to bed bug lethal temperature (and killing the bed bugs). However, it was also found that none of the heat systems tested killed all of the sentinel bed bugs in every replicate. Therefore, we learned heat treatments cannot be expected to eliminate each and every bed bug in a home, and that supplemental control products such as desiccants dusts should be applied after every heat treatment. When attempting to determine which heat system was the most effective for killing bed bugs, it was determined that regardless of which heat systems was being used, the attention and activity (monitoring temperatures and adjusting equipment) of the heat treatment technician was the most important factor contributing to bed bug mortality as well as the achievement of bed bug lethal temperatures in cracks and crevices for all three systems. Our second study examined the environmental factors that influenced fungal growth after bed bug exposure to the insecticidal product Aprehend® (active ingredient Beauveria bassiana). Over the last several decades, this fungus has been widely used to control multiple insect pests. Recently, it has been labelled for bed bug control in indoor environments. This second study was intended to determine the atmospheric conditions (temperature and humidity) under which Aprehend sporulation was most effective for killing bed bugs. It was found that humidity conditions of 30-50% combined with temperatures of ~21°C produced the highest frequency of fungal infection and the shortest median bed bug survival time. This result was surprising because it was originally hypothesized that the 70% humidity condition would be equally effective for promoting fungal growth. However, at all of the temperatures tested, bed bug fungal infection rates at 70% humidity were not as high as those observed when the humidity was within the 30-50% range. Therefore, this study was able to document that the temperatures and humidity combinations that would typically be found within human homes (21oC at 30-50% humidity) were the most effective for producing fungal infections when bed bugs were exposed to the Aprehend product. The final study addressing novel methods for controlling insecticide resistant bed bugs investigated the efficacy of using Vikane gas fumigant (sulfuryl fluoride) at the 1.9× dosage rate for eliminating bed bugs in two challenging infestation situations: personal vehicles, and confined spaces densely packed with personal belongings. The vehicles used in this study were large minivans with seating that folded into the floor. The confined spaces were cargo trailers filled to 85% capacity with books, furniture, and other household items. Each van and trailer was equipped with ~90 sentinel bed bugs consisting of three groups of 9-11 bed bug eggs, 10 nymphs, and 10 adults. The Vikane Fumiguide calculator was used to determine the target dosage (g-h/m3) to apply in each replicate (e.g., one van or trailer). Sulfuryl fluoride concentrations were measured throughout the fumigation process using a Spectros SF-ReportIR. Concentration readings were input into the Fumiguide to determine when the accumulated dosage (g-h/m3) was achieved, and when aeration should be initiated. After aeration was complete, the sentinel bed bugs were removed from the replicates and bed bug nymph and adult mortality was recorded. Bed bug eggs were monitored for 23 d to determine latent mortality. Fumigated bed bug mortality for each replication was 100% regardless of life stage. Latent mortality was observed in a single bed bug egg, where the nymph never fully hatched. This study determined that fumigation with sulfuryl fluoride at the 1.9× dosage factor is an effective method for eliminating insecticide resistant bed bugs from vehicles and personal belongings in densely packed situations. Overall, it was found that the Beauveria bassiana product was most effective when applied under atmospheric conditions that are typically found in indoor home environments. This discovery was very reassuring, because the Aprehend product is one of very few that actually have residual activity with regard to bed bug control. This study also found that whole home heat treatments require rigorous pest technician attention and monitoring to achieve the best results. It was also determined that heat treatments cannot be assumed to be 100% effective on their own, and that they should be supplemented with additional (residual) treatment applications. Not surprisingly, fumigation with sulfuryl fluoride was determined to be 100% effective for eliminating bed bugs in personal belongings that had been packed into treatment chambers. The fumigation process also proved to be 100% effective for eliminating bed bug infestations in transport vehicles which cannot not be adequately treated and are at risk for having electronic components damaged if treated with heat.
- Masters Theses