Selection of surfactants for enhancing the wettability of powder formulations of Beauveria bassiana (bals.-criv.) vuill. (1912) (ascomycota: Cordycipitaceae)

摘要

Entomopathogenic fungal products, such as formulations made with Beauveria sp., are recognized for their effectiveness in controlling insect pests. Due to their high hydrophobicity, however, fungal agents require the addition of surfactants to diminish particle aggregation in water during field applications. The aim of the present study was to select surfactants to enhance the wettability of Beauveria bassiana formulations without affecting fungal viability. In a first experiment, formulations prepared with 24 different surfactants were tested for viability after 30 days of storage at 25 degrees C. Five surfactants provided the best results and were selected for further experiments. New formulations were prepared and evaluated in terms of surface tension, wetting time, conidial germination, and viability during three months of storage. The biological index was also evaluated. The shortest wetting time (1.61 min) and lowest surface tension (38 mN/m) were obtained using Emulsogen TS 200 at 5%. Four of the five formulations led to a 50% decrease in germination after two months of storage. The exception was Surfon D. After three months of storage, the control formulation (without surfactant) and formulations prepared using Surfom D had germination rates of 0% and 55%, respectively. The highest viability (1.14 x 10(9) colony-forming units/g) was obtained with Surfom D. B. bassiana was found to be compatible with 5% Emulsogen TS 200 and Surfom D. Emulsogen TS 200 was more effective at reducing surface tension but decreased fungal viability and conidial germination. Surfom D exhibited poor wetting properties but increased the germination rate of B. bassiana. Therefore, the use of both surfactants is promising for the formulation of B. bassiana pest control products.