A fungal isolate was detected on a dead Triatoma sordida (Stål) collected in a peridomestic area in central Brazil. The fungus belongs to Evlachovaea Borisov and Tarasov, a new genus that was recently described in Russia. The isolate seems to be a third species and the second new and undescribed species from Brazil. The fungus was shown to be active against Triatoma infestans (Klug) third-instar nymphs at a humidity close to saturation. However, activity was reduced at a lower humidity (75%). Values of LC₅₀ varied between 1.1 × 10⁵ and 1.5 × 10⁴ conidia/cm² treated surface, 15 and 20 d after fungal application and incubation at humidity close to saturation. This new fungus may have a potential for biological control of peridomestic Chagas’ disease vectors during the rainy season.