Does the fungus among us increase trap fidelity? Mycelium carbon dioxide generators for mosquito (Diptera: Culicidae) traps in two ecoregions of the United States

Mosquito control programs deploy mosquito traps for surveillance and targeting of vector mosquitoes. The primary attractant in these traps is generally carbon dioxide (CO2), which acts as a powerful long-distance lure. Historically, dry ice and compressed gas have been accessible as lures, but they may exhibit logistical hardships (storage, safety, equipment, calibration, consistency, etc.). Additionally, the aforementioned standards can be inaccessible in remote or low-resource environments. Microbial lures have often been proposed to bridge this gap, but prior options, such as yeast, have proven inferior compared to traditional CO2 lures. However, a mycelium-based CO2 generator, the Exhale CO2 Bag, is now commercially available. Initial studies suggested this product may be suitable for mosquito surveillance. To validate this, semi-field cage assays were conducted in Florida by releasing several species of vector mosquito into enclosures to be recollected by either Biogents or United States Centers for Disease Control and Prevention (CDC)-style traps paired with the Exhale, gas cylinders, dry ice, or unbaited. Dry ice and compressed gas performed equivalently, with Exhale collecting 25% to 50% fewer mosquitoes, and unbaited traps collected 10% to 30% fewer than Exhale. Additionally, field testing in Utah, with traps deployed across rural wetlands, industrial transition areas, and urban metropolitan areas, all yielded the same result: the Exhale mycelium and unbaited traps collected an average of 35 or fewer mosquitoes, as compared to regulated gas CO2 traps collecting 1,000 to 3,000 mosquitoes in the same areas. Though some merits exist for a mycelium-based trap, the current data and recent literature fail to support this technology for host-seeking traps in existing mosquito surveillance programs.