Fungi are more than decomposers. They can infect many different organisms, including insects. It is due to the fact that fungi have the ability to infect insects that humans have a long history of using them for the biological control of pests. For instance, Beauveria bassiana was first identified as a silkworm pathogen in 1815. In 1879, Elie Metchnikoff, a Russian zoologist suggested using Metarhizium anisopliae to control beetles of agricultural crops.
Some fungi have evolved to be generalist pathogens, killing many different species of insects. Other fungi are specialists that have a narrow range of insects they can target, for example, some fungi kill a single species of ant (Fig 1).
Mosquitos, and the diseases they vector, are still a worldwide issue. Over 200 million people contract malaria each year. These cases largely occur in sub-Saharan Africa, and in recent years incidence of malaria has plateaued, instead of diminished. This is largely because pyrethroids, the class of insecticides largely used for mosquito control, are losing their efficacy. Without new methods to control mosquito populations in malaria endemic areas, the risk of malaria incidence rising is a real threat.
Recent advances have allowed scientists to modify fungi that can be used for insect control. The St. Leger lab at the University of Maryland developed a transgenic bioinsecticide by using Hybrid toxin, originally derived from the venom of the Australian Blue Mountains funnel-web spider, and inserted it into the genome of Metarhizium pingshaense. Because this toxin has several targets in insect neurons, there is a low chance of mosquitoes developing resistance to it . The team also found Hybrid-expressing fungus was more effective at killing mosquitos.
This team was conscientious of socio-economic needs in their experimental design. For the project to be successful, applications would need to be cost effective. The cotton cloths used in their trials and the sesame oil are both readily available and inexpensive. Brian believes using the transgenic Hybrid strain with a single re-application would remain effective throughout the whole rainy season.
There are many remaining steps before field application of such a transgenic fungus can occur. The next step for this group is to earn stakeholder approval for field testing. This team needs to work directly with regulatory bodies in Burkina Faso and with community members before they can attempt a field trial. Field trails assessing ecological risk and demonstrating successful entomological, then epidemiological endpoints are essential before the sale and distribution of transgenic fungus for biocontrol.
 Liao X, Fang W, Lin L, Lu H-L, Leger RJS (2013) Metarhizium robertsii Produces an Extracellular Invertase (MrINV) That Plays a Pivotal Role in Rhizospheric Interactions and Root Colonization. PLoS ONE 8(10): e78118. https://doi.org/10.1371/journal.pone.0078118
 Lovett, B., Bilgo, E., Millogo, S. A., Ouattarra, A. K., Sare, I., Gnambani, E. J., … St. Leger, R. (2019, May 31). Transgenic Metarhizium rapidly kills mosquitoes in a malaria-endemic region of Burkina Faso. Science, 894–897.
 Bilgo, E., Lovett, B., Fang, W., Bende, N., King, G. F., Diabate, A., & St Leger, R. J. (2017). Improved efficacy of an arthropod toxin expressing fungus against insecticide-resistant malaria-vector mosquitoes. Scientific reports, 7(1), 3433. doi:10.1038/s41598-017-03399-0
Huiyu Sheng is a second year master’s student in the St. Leger lab, studying on entomo-pathogenic fungi and their relationship with both plants and insects.
Zac Lamas is a second year PhD student studying the feeding behavior of Varroa destructor mites.