Location: Crop Bioprotection Research
2018 Annual Report
Objectives
Objective 1. Enable the commercial production of microorganisms pathogenic to mosquitoes.
Objective 2. Enable the commercial production of bioactive compounds/metabolites derived from plants and microorganisms to control mosquitoes and/or the viruses they carry.
Approach
Our approach will focus on the discovery of novel microbial and plant-based biopesticides that could be commercialized for the control of mosquitoes or the pathogens they transmit. A variety of entomopathogenic fungi will be evaluated for their effect on survival of adult mosquitoes. Selection of candidate mosquito entomopathogens will be done initially by focusing on the isolates with known pathogenicity and strains that have previously been isolated from dipteran species. Transcriptomic analysis coupled with functional assays (through reverse-genetic techniques) will be used to identify the fungal mode of action as well as the mosquito responses to infection. Attempts will be made to isolate and identify microbe-derived molecules with biological activity against mosquitoes and selected arboviruses. We will also evaluate plant-based compounds effective for activity against mosquitoes. We will integrate standard insecticide testing bioassays with modern and conventional approaches in chemical ecology to identify the chemical compounds in selected plants that are attractive to gravid females and deleterious to mosquito larvae.
Progress Report
Our research group was engaged in a variety of research activities to enable the commercial production of microbe- and plant-derived bioactive compounds that are pathogenic to mosquitoes and/or the viruses they carry. Substantial progress has been made in the first year of this research project.
ARS scientists in Peoria, Illinois made significant progress in Objective 1 by characterizing the gut microbial communities of the white dotted mosquito (Culex restuans) in relation to parental background. ARS scientists in Peoria, Illinois successfully developed and optimized the protocols for studying how mosquitoes interact with entomopathogenic fungi. Additionally, ARS scientists in Peoria, Illinois successfully examined the effects of selected entomopathogenic fungal strains on mosquito survival, and identified the antifungal responses mounted by the mosquito in response to the fungal challenge.
For Objective 2, ARS scientists in Peoria, Illinois successfully examined the potential to exploit common blackberry (Rubus allegheniensis) leaves as a tool for mosquito control in storm water catch basins, the primary larval habitats for the West Virus vector, Culex (Cx) pipiens. ARS scientists in Peoria, Illinois combined conventional oviposition choice bioassays with standard and current state-of-the-art microbiological and molecular techniques to examine the role of microbial communities and chemical compounds associated with leaves of common blackberry in influencing Cx. pipiens oviposition behavior and larval survival and development. ARS scientists in Peoria, Illinois also evaluated a variety of essential oils extracted from local plants or purchased from commercial vendors as potential larvicides for mosquito control. These studies have resulted in the identification of novel plant-based tools and strategies that can be used as part of integrated vector management. With regard to identification of bioactive compounds from microbes, ARS scientists in Peoria, Illinois have generated a catalog of microbes with potential for bioactive compound production and assigned their antibacterial properties using bacteria isolated directly from lab-reared and field-collected mosquitoes. This list is currently being expanded by testing additional fungal strains.
Accomplishments
1. Common blackberry and mosquito control. In efforts to discover new mosquito control tools that can complement or even replace the use of toxic synthetic chemicals, this research examined whether leaves of common blackberry can be used as a tool for mosquito control in storm water catch basins. ARS researchers at Peoria, Illinois, discovered that “treating” storm water catch basins with leaf litter of common blackberry increased the number of Cx. pipiens egg rafts that were laid in these man-made habitats but reduced the number of emerging adult mosquitoes. These findings indicate that common blackberry leaf infusion acts as an ecological trap — a low quality habitat that is preferred over other available high quality habitats. Oviposition choice and larval survivorship bioassays indicate that attraction of gravid female mosquitoes to common blackberry infusion is mediated by chemical cues released as the leaves decomposed while larval survivorship is limited not by the toxic compounds present in the common blackberry leaves but by the failure of bacterial communities thriving in the common blackberry leaf infusion to meet the nutritional requirements for mosquito larvae. These findings provide an experimental proof-of-concept for a new, inexpensive, environmentally safe, and effective “attract-and-kill” integrated vector management tool for mosquito control.
2. Essential oils and mosquito control. Although essential oils are known to elicit a variety of biological activities against mosquitoes, only a limited number of essential oil-based biopesticides are commercially available. In an effort to increase this number, this research examined the potency of some essential oils and their combinations against mosquito larvae. ARS researchers at Peoria, Illinois, discovered that a combination of Manuka and oregano essential oils had synergistic effects against mosquito larvae that have the potential as an alternative to synthetic insecticides. The researchers also found that garlic and asafoetida essential oils were highly toxic to mosquito larvae but became less toxic when combined. These findings increase the number of essential oils that are known to exhibit larvicidal activity against mosquitoes. The findings also demonstrate the need for knowledge-guided decision-making process when selecting essential oil combinations for use in mosquito control since some essential oil combinations can undermine vector control programs.
3. Invasive alien plants and mosquito-borne diseases. Despite the ubiquity of invasive alien plants in many ecosystems, their impact of human risk of exposure to mosquito-borne diseases is not well understood. ARS researchers at Peoria, Illinois, in collaboration with researchers at the University of Maine and the University of Illinois, investigated how Amur honeysuckle (Lonicera maackii), an invasive alien plant species can influence the risk of mosquito-borne diseases. The researchers discovered that Amur honeysuckle supports diverse bird communities and large populations of vector mosquitoes. Removal of this invasive alien shrub resulted in significant reduction in mosquito populations and loss of bird communities that are susceptible to West Nile virus including American robin, house sparrow, blue jay, and common grackle. These results suggest that this invasive alien shrub can act as a risk factor for mosquito production which may in turn increase the risk of human and livestock exposure to mosquito-borne diseases.
4. Identification of entomopathogenic fungi with mosquitocidal activity. The rapid and widespread development of insecticide resistance in mosquitoes and the increase in the incidence of mosquito-vectored diseases calls for the development of alternative methods of mosquito control. The use of fungi to control mosquitoes is an environmentally-friendly alternative to chemical pesticides. ARS researchers at Peoria, Illinois, have identified new strains of fungi that kill the major mosquito vector Aedes aegypti. The scientists also found differences in the way each fungal pathogen kills the mosquito, revealing novel compounds produced by the fungi that the researchers are working to develop as new mosquito control technologies. In addition, the information gained from these studies improves the design of microbial control strategies, for instance, through the selection of fungal entomopathogens with previously unidentified modes of action. Strategies using a combination of fungi with different modes of action will allow us to prevent/retard the development of resistance to these entomopathogenic fungi and also to accelerate their speed of kill.
5. Molecular characterization of mosquito responses to entomopathogenic fungal infection. The ability of a mosquito to survive a fungal infection depends on how efficiently its immune system recognizes the fungus so that it can appropriately respond and control the infection. In a groundbreaking new study, ARS scientists at Peoria, Illinois, found that species of the fungal genus Isaria produce compounds that suppress the mosquito immune system. This new information is a major departure from what has been described in the literature for other types of entomopathogenic fungi that are used to control mosquitoes and other insect pests. Successful development of these new compounds will provide new technologies for the control of mosquito populations that are environmentally-friendly and target-specific.
Review Publications
Muturi, E.J., Ramirez, J.L., Zilkowski, B.W., Weiler, L., Rooney, A.P. 2018. Ovicidal and larvicidal effects of garlic and asafoetida essential oils against West Nile virus vectors. Journal of Insect Science. 18(2):43. doi: 10.1093/jisesa/iey036.
Muturi, E.J., Ramirez, J.L., Rooney, A.P., Kim, C. 2017. Comparative analysis of gut microbiota of Culex restuans (Diptera: Culicidae) females from different parents. Journal of Medical Entomology. 10:163-171. doi: 10.1093/jme/tjx199.
Dowd, P.F., Zilkowski, B.W., Johnson, E.T., Berhow, M.A., Muturi, E.J. 2018. Transgenic expression of a maize geranyl geranyl transferase gene sequence in maize callus increases resistance to ear rot pathogens. AGRI GENE. 7:52-58. https://doi.org/10.1016/j.aggene.2018.01.001.
Karki, S., Westcott, N.E., Muturi, E.J., Brown, W.M., Ruiz, M.O. 2017. Assessing human risk of illness with West Nile virus mosquito surveillance data to improve public health preparedness. Zoonoses and Public Health. 65:177-184. doi: 10.1111/zph.12386.
Weiler, L., Rooney, A.P., Behle, R.W., Muturi, E.J. 2017. Characterization of Tolypocladium cylindrosporum (Hypocreales: Ophiocordycipitacea) and its impact against Aedes aegypti and Aedes albopictus eggs at low temperature. Journal of the American Mosquito Control Association. 33(3):184-192.
Moise, I.K., Riegel, C., Muturi, E.J. 2018. Environmental and social-demographic predictors of the southern house mosquito Culex quinquefasciatus in New Orleans, Louisiana. Parasites & Vectors. 11:249. doi.org/10.1186/s13071-018-2833-5.
Muturi, E.J., Ramirez, J.L., Doll, K.M., Bowman, M.J. 2017. Combined toxicity of three essential oils against Aedes aegypti (Diptera: Culicidae) larvae. Journal of Medical Entomology. 54:1684-1691. doi: 10.1093/jme/tjx168.
Ramirez, J.L., Dunlap, C.A., Muturi, E.J., Barletta-Ferreira, A.B., Rooney, A.P. 2018. Entomopathogenic fungal infection leads to temporospatial modulation of the mosquito immune system. PLOS Neglected Tropical Diseases. 12:e0006433. https://doi.org/10.1371/journal.pntd.0006433.
Gomes, F.M., Hixson, B.L., Tyner, M.D., Ramirez, J.L., Canepa, G.E., Alves E Silva, T.L., Molina-Cruz, A., Keita, M., Kane, F., Traore, B., Sogoba, N., Barillas-Mury, C. 2017. Effect of naturally-occurring Wolbachia in Anopheles gambiae s.l. mosquitoes from Mali on Plasmodium falciparum malaria transmission. Proceedings of the National Academy of Sciences. 114:12566-12571. doi: 10.1073/pnas.1716181114.
Gardner, A.M., Muturi, E.J., Overmier, L.D., Allan, B.F. 2017. Large-scale removal of invasive honeysuckle decreases mosquito and avian host abundance. EcoHealth. 14:750:761. doi: 10.1007/s10393-017-1265-6.
Ramirez, J.L., Muturi, E.J., Dunlap, C.A., Rooney, A.P. 2018. Strain-specific pathogenicity and subversion of phenoloxidase activity in the mosquito Aedes aegypti by members of the fungal entomopathogenic genus Isaria. Scientific Reports. doi:10.1038/s41598-018-28210-6.
