Evaluation of potential biocontrol agents against Claviceps africana in vitro and in vivo

Undiluted culture filtrates of two commercial products of Trichoderma spp., Trichopel and Trichoflow, and two isolates of Penicillium citrinum completely inhibited the conidial germination of macroconidia of Claviceps africana , the cause of ergot or sugary disease of sorghum (Sorghum bicolor) in vitro . Similarly, Pseudomonas aeruginosa and Burkholderia cepacia completely inhibited macroconidial germination, with the former being more effective at high dilutions. In contrast, these bacterial isolates failed to inhibit infection in vivo in glasshouse tests with ergot-inoculated sorghum, but all fungal biocontrol agents (including an isolate of Epicoccum nigrum) reduced the severity of disease (percentage of infected spikelets per panicle), in some cases completely inhibiting the development of ergot. In a second glasshouse trial, optimum control was achieved when the biocontrol agents were applied 3-7 days before inoculation with conidia of C. africana .