The alarm-defense system of Cimex lectularius and its implications for pest management
Post by Lisa Kuder
Field site data from the DC Metro area were analyzed to determine how current chemical controls (contact aerosol sprays, liquid residuals, and dusts) compare to that of heat treatment (mobile heating units). Building types (single-family homes, row homes, multifamily apts., and commercial properties) were included in the analysis to determine if certain building types have greater potential for reinfestation (Ulrich 2015). Of the 4,258 units evaluated over a 3 year period, heat treatment required a lower percentage of retreatment than did chemical controls, 9.5% and 20.8% respectively, and multifamily apts. were the most susceptible to reinfestation (Ulrich 2015). Overall heat treatments were more effective at eliminating bed bugs. However, neither was 100% successful and both methods have several major disadvantages (Ulrich 2015). Thus the impetus for developing novel bed bug detection and treatment solutions.
Dr. Ulrich’s research focused on multiple aspects of bed bug management, including alternative control strategies. Specifically he investigated how bed bug communication pheromones, in particular their alarm-defense system, interact with a promising candidate for pest control, a naturally occurring insect pathogenic fungus. In addition, he determined whether these pheremones could be used as a monitoring tool for determining whether bed bugs are present. Bed bug communication pheremones have previously been isolated with two common aldehyde major components: (E)-2-hexenal and (E)-2-octenal (Siljander et al. 2008, Gries et al. 2014). Both aldehydes have antibacterial and antimicrobial properties, therefore they have the potential to inhibit the growth of fungal spores. Metarhizium anisopliae, a ubiquitous soil dwelling fungus, has been extensiveily studied as a tool for regulating pest insects in agrosystems and greenhouses (Tiago et al. 2014). While deadly to insects, primarily beetle larvae, it is non-toxic to humans and mammals (EPA 2003). To determine whether M. anisopliae impacts bed bug survival, ingestion assays were performed using 4 different concentrations of M. anisopliae spores added to blood. As seen in Figure 2 below, bed bugs are indeed susceptible to M. anisopliae, particularly at higher spore concentrations (Ulrich et al. 2014).
In conclusion, commercial treatments are not entirely effective and have several major drawbacks. Thus, there is a real need and demand for novel solutions in the bed bug control industry. M anisopliae, a naturally occurring insect pathogenic fungus, shows some promise as an alternative method for controlling bed bug infestations (Ulrich et al. 2014). However, as demonstrated by the present research, several hurdles exist. Bed bugs are susceptible to M. anisopliae but only at high relative humiditities (> 98%), levels impractical in the field (Ulrich et al. 2014). Also, two common alarm pheremones (2-hexenal and 2-octenal) in bed bug communication inhibit the growth of M. anisopliae at field relevant concentrations (Ulrich et al. 2015). Despite their drawbacks for management, these pheremones, 2-hexenal and 2-octenal, did show potential as monitoring tools for determining bed bug presence, as bed bugs were attracted to both aldehydes at low concentrations (Ulrich et al. 2015). Given the desire for alternative treatment methods, Dr. Ulrich’s findings are encouraging and will likely inspire further investigations into innovative solutions to controlling the commmon bed bug.
El Damir, M. “Variation in germination, virulence and conidial production of single spore isolates of entomopathogenic fungi in response to environmental heterogeneity.” Journal of Biological Science, 6 (2006), pp. 305–315
Gries, Regine, et al. "Bed Bug Aggregation Pheromone Finally Identified." Angewandte Chemie 127.4 (2015): 1151-1154.
Siljander, Eric, et al. "Identification of the airborne aggregation pheromone of the common bed bug, Cimex lectularius." Journal of chemical ecology 34.6 (2008): 708-718.
Tiago, Patricia Vieira, Neiva Tinti de Oliveira, and Elza Áurea de Luna Alves Lima. "Biological insect control using Metarhizium anisopliae: morphological, molecular, and ecological aspects." Ciência Rural 44.4 (2014): 645-651.
Ulrich et al. “Exposure of bed bugs to Metarhizium anisopliae at different humidities.” Journal of Economic Entomology 107 (2014): 2190-2195.
Ulrich et al. “Inhibition of the entomopathogenic fungus Metarhizium anisopliae in vitro by bed bug defensive secretions (E)-2-hexenal and (E)-2-octenal.” BioControl doi (2015): 10.1007/s10526-015-9667-2.
Ulrich, Kevin. “The alarm-defense system of Cimex lectularius and its implications for pest management” UMD thesis defense Dept. of Entomology (2015).
US Environmental Protection Agency Office of Pesticide Programs. “Biopesticides registration action document -- Metarhizium anisopliae strain F52 (PC Code 029056)” (2003).
About Lisa: She is a 1st year PhD student in the Dennis vanEngelsdorp’s bee lab. She will be studying the biology and expansion of Anthophora plumipes, a species that has recently naturalized in the Mid-Atlantic region, and more generally exploring options for maximizing nesting sites for ground-nesting bees.