Mesaqueuri Mota Nonato¹, Kemily Nunes da Silva Moya¹, Jackeline da Silva Luciano¹, Claudia Maria Ríos-Velasquez¹, Priscila Ferreira de Aquino¹

Dengue is the most prevalent arboviral disease in Brazil, with 6.5 million probable cases reported in 2024. Vector control of the Aedes aegypti mosquito, the main vector of the arbovirus in the country, is the most widely used mitigation strategy. Chemical control was widely used, but indiscriminate use resulted in the emergence of resistant populations. Given this, fungus-based products present themselves as a promising alternative due to their high host specificity and ability to act through contact or ingestion. Among these, the genus Trichoderma stands out for its wide biotechnological application, already being described as an antagonist of aphids and culicids. Thus, we sought to evaluate the mortality and behavioral changes of Ae. aegypti larvae exposed to Trichoderma harzianum and T. asperellum. For this, strains of T. harzianum (CFAM1308) and T. asperellum (CFAM0256) were reactivated, authenticated, and acquired from the Amazon Fungus Collection of the Leônidas and Maria Deane Institute (ILMD/Fiocruz Amazônia). Third instar larvae of Ae. aegypti were obtained from a colony in the insectarium of the Laboratory of Infectious Diseases Ecology in the Amazon at ILMD/Fiocruz Amazônia. Conidia suspensions were prepared in five concentrations, which were applied to Ae. aegypti larvae and evaluated for 7 days. The bioassays were performed in quintuplicate and repeated twice, and the data obtained were submitted to statistical analysis using GraphPad Prism software. To analyze larval behavior, an additional bioassay was performed with the most virulent concentration, in which larval mortality was monitored every 3 hours for 7 days. In addition, the larvae from these tests were subjected to optical microscopy. The results showed that the larval mortality rate increased as the inoculum concentration was increased. The concentration of 1x10⁸ conidia/mL proved to be the most lethal, causing the mortality of 88.5% of the larvae exposed to T. asperellum and 86.5% in T. harzianum. Specifically, mortality began after 6 hours of exposure in both treatments. After 9 hours, larvae treated with T. asperellum showed sluggish movements, a behavior observed in T. harzianum only after 12 hours. After 24 hours, 63% of the larvae exposed to T. harzianum died, while T. asperellum affected only 24%. At the end of the bioassays, a delay in the development of individuals was observed in both fungal treatments, preventing them from reaching the pupal stage. Optical microscopy revealed the presence of T. harzianum and T. asperellum spores adhering to the mouth and abdomen of the larvae, as well as partial darkening of the abdomen, suggesting the possible presence of conidia inside the intestine. These results demonstrate the larvicidal potential of Trichoderma asperellum and T. harzianum and may serve as a basis for future studies aimed at developing new control strategies for the immature stages of Aedes aegypti.

Agradecimentos: FAPEAM (POSGRAD Program and Public Call No. 010/2021 –Priority Areas in CT&I Program), CAPES (Funding Code 001), and PROEP/ILMD-FIOCRUZ AMAZÔNIA – LDMAIS.