Screening of surfactants for entomogenous fungus Isaria fumosorosea PF904

In order to identify effective surfactants for Isaria fumosorosea PF904, the surface free energies of the leaves of cabbage, apple, eggplant and cucumber were measured by the OWRK method. When 4 different surfactants were added respectively into the spore suspension of Isaria fumosorosea, the surface tension and critical micelle concentration (CMC) of each solution were determined by the surface tension method. Their contact angle and maximum retention (R_m) on plant leaves were measured by angle measuring and weight difference method. Safety assessments of these screened surfactants were also conducted. The results showed that the wetting ability of Isaria fumosorosea spore suspension on 4 types of the tested plant leaves were improved when 125-500 mg/L of OFX-0193, AOS or Nekal was added. Nekal (250 mg/L) functioned best on cabbage and apple leaf surfaces(R_m: 11.90±0.23 and 13.28±0.28 mg/cm²; contact angle: 29.5°, 27.5°), indicating its advantage in promoting the wetting ability of Isaria fumosorosea PF904. OFX-0193 showed the best maximum retention at the concentration of 9.45 mg/cm² on the surface of eggplant leaf at the concentration of 125 mg/L. Pullulan surface tension values were greater than the surface free energy values of cabbage, apple and eggplant leaves. Its contact angles were greater than 90° when reaching the concentration of CMC, which revealed that it was not effective in the activating of the wetting ability of PF904. The results of the inhibition rates of spore germination measurement showed that Nekal and OFX-0193 did not restrain Isaria fumosorosea PF904 germination, but AOS did. In conclusion, surfactants Nekal and OFX-0193 can be employed to assist Isaria fumosorosea to protect apple and cabbage from pests, OFX-0193 can also be used to control eggplant pests.