A mycelium-based carbon dioxide source for trapping vector mosquitoes

Carbon dioxide (CO2) is a key activator and attractant for mosquitoes during host-seeking and is routinely used to bait traps. However, deploying CO2 via dry ice, compressed gas, sugar-yeast reactions, or carbonate-acid systems can be expensive, short-lived, and labor-intensive. We evaluated the effectiveness of a commercially available, mycelium-based CO2 source (ExHale bag) for attracting mosquitoes to passive and active traps. Originally developed for greenhouse use, the ExHale bag provides sustained CO2 release for up to 6 mo. Under semi-field conditions, we compared Biogents gravid Aedes traps (BG-GAT) with and without ExHale using single or mixed groups of 3 vector mosquito species (Culex quinquefasciatus, Aedes albopictus, and Aedes aegypti). A field validation was also conducted to assess the efficacy of ExHale in both BG-GAT and BG-Sentinel traps. Our semi-field findings revealed that BG-GATs baited with ExHale captured significantly more mosquitoes than unbaited traps in both single-species (15.2 to 92.3×) and mixed-species (21.7×) tests. In field trials, ExHale-baited BG-GATs collected significantly more mosquitoes, including a broader range of species, at coastal forest (9.1×) and suburban (47.5×) sites. BG-Sentinel traps baited with ExHale also collected more female mosquitoes (1.4×), though the difference was not statistically significant. Our results indicate that ExHale, when coupled with a passive trap, provides an economical and effective trapping system for vector mosquitoes. The long effective period of CO2 production is advantageous for large-scale mosquito surveillance, particularly in remote field sites and developing countries, where CO2 may be prohibitively expensive or difficult to obtain.