The high biocontrol efficacy may be due to the intensive colonization of antagonistic strains on the surface of the banana roots (Ling et al. 2010). The ability of W19 and W2 strains to form biological films was investigated. After incubation for 24 h at 37 °C, a very thick biological film could be detected from the treated W19 strain. The W2 strain could also form a biological film, which was thinner than the W19 strain (Fig. 3). We have selected W19 strain for further studies due to its superior biocontrol efficiency and ability to form a thick biological film