Seleção de tensoativos e avaliação de compatibilidade com Beauveria bassiana para desenvolvimento de formulação WP

Abstract

Entomopathogenic fungal products such as Beauveria sp. formulations are recognized for their effectiveness in controlling insect pests, attributed to the ability to adhere to the insect cuticle through hydrophobins. However, because of their high hydrophobicity, fungal agents require the addition of surfactants to reduce particle aggregation during application. This study aimed to select surfactants that can improve the wettability of Beauveria bassiana formulations without affecting fungal viability. In a first experiment, formulations prepared using 25 different surfactants were tested for viability after 30 days of storage at 25 °C. Six surfactants provided the best results and were selected for further experiments. New formulations were prepared and evaluated for surface tension, wetting time, conidial germination, viability, and biological index during 3 months of storage. Subsequently, through central composite design (DCC) the optimal concentration range for the two selected surfactants was determined. The shortest wetting time (1.61 min) and lowest surface tension (38 mN/m) were obtained using Emulsogen TS 200 at 5%. All six formulations showed a decrease in germination after 1 month of storage. After 3 months of storage, the control formulation and formulations prepared using Surfom D had germination rates of 0% and 55%, respectively. The highest viability (1.14 × 109 colony-forming units/g) was obtained with Surfom D. B. bassiana was found compatible with 5% Emulsogen TS 200 and Surfom D. Emulsogen TS 200 was the most effective in reducing surface tension but decreased fungal viability and conidial germination. Surfom D showed poor wetting properties but increased B. bassiana germination rate. The combination of both surfactants seem a good option and was evaluated through DCC. The optimum region is around was 3% of each of the surfactants in the composition of a formulation for the variables surface tension, wetting time, germination and CFU. The stability of the B. bassiana formulation containing 3% Emulsogen TS 200 and Surfom D is 2 months at room temperature (25 ° C).