Native fungi from Amazon with potential for control of Aedes aegypti L. (Diptera: Culicidae)

Abstract

Aedes aegypti L. (Diptera: Culicidae) is the main transmitter of pathogens that cause human diseases, including dengue, chikungunya, zika and yellow fever. Faced with this problem, this study aims to select fungi with entomopathogenic potential against Ae. aegypti and develop formulations that optimize the control action of entomopathogenic fungi in the semi-field condition. 23 fungal strains native from Amazon were inoculated in Potato-Dextrose-Agar (PDA) culture medium for 14 days and then transferred by scraping to tubes containing 0.9% NaCl solution. To obtain the larvae, eggs were collected using traps in peridomestic environments for 7 days. 20 larvae of Ae. aegypti in 125 mL erlenmeyers containing 20 mL of conidial suspension at a concentration of 1x106 conidia/mL for initial selection and 1×104, 1×105, 1×106 and 1×107 conidia/mL for determination of LC50. Mortality was checked every 24 h for 5 days. The three fungi with the best virulence rates were identified using molecular techniques. The compatibility between fungi at a concentration of 1×106 conidia/mL and oily adjuvants, mineral oil and vegetable oil (andiroba, chestnut and copaiba) at concentrations of 0.1, 0.5 and 1% was evaluated. The germination capacity of 100 conidia per treatment was evaluated after incubation at 28 ºC for 24 h. To evaluate the entomopathogenic potential of the fungal formulations, conidial suspensions (1×106 conidia/mL) were added with 0.1% mineral and vegetable oil. The treatments were submitted to laboratory and semi-field conditions and mortality was verified every 24 h for 5 days. Beauveria sp. (4,458) (LC50 = 8.66× 103), Metarhizium anisopliae (4,420) (LC50 = 5.48×104) and M. anisopliae (4,910) (LC50 = 1.13×105) were significantly more effective in the larval control of Ae. aegypti, in relation to the other fungal morphospecies evaluated. Mineral oil was better compatible in all treatments evaluated. Beauveria sp. (4,458) was considerably less virulent under semi-field conditions. M. anisopliae (4,910) formulated with mineral oil increased larval mortality to 100% on the 4th day in the laboratory and on the 5th day in the semi-field. Fungal formulations developed from native Amazonian isolates represent a promising tool for the development of strategies to control Ae. aegypti.