The effect of biofungicide Mycostop on Ceratocystis radicicola, the causal agent of black scorch on date palm

In vitro studies were conducted to assess the efficacy of the biofungicide Mycostop on the fungus Ceratocystis radicicola (= Ceratostomella radicicola), which causes black scorch on date palm (Phoenix dactylifera) and the effect salinity on the growth of Streptomyces griseoviridis, the active component of Mycostop. C. radicicola was isolated from roots of diseased date palm in landscape settings, nurseries, and plantations. In vitro, the effective concentration (EC₅₀) of Mycostop that reduced the mycelial growth by 50% was 0.35 g/l of PDA. Mycostop at the rate of 0.35 g/l or greater reduced spore germination, plasmolyzed germlings and reduced sporulation of C. radicicola. In essence it reduced the inoculum potential of C. radicicola. In sterile soil treated with Mycostop, root pieces of date palm inoculated with C. radicicola were less necrotic than those in untreated soil. Streptomyces griseoviridis in Mycostop did not grow on PDA amended with 5.0% NaCl (-4.28 MPa), but the number of colony formed units on PDA amended with 1.0 to 4.0% NaCl was not significantly different from a factor that was considered if Mycostop is to be used to manage black scorch in Kuwait. The observations showed the effects of Mycostop on C. radicicola in laboratory studies but its efficacy on black scorch disease of date palms in nurseries and plantations is yet to be determined.