The objective of this study was to evaluate the pathogeneicity of some isolates of Beauveria bassiana for the control of insect pests such as Prostephanus truncatus and Stophilus zeamais, in stored maize cobs. Beauveria pathogenecity was also evaluated on Teritriosoma nigrescens, a natural predator of P. truncatus. Conidia of the fungi were mixed with kaolinite and applied to stored maize, 450 cobs arranged in layers of 50. Two trials were established, in the first trial applications of the fungi was done at the moment of storing the maize. In the second trial, applications of the fungi were evaluated after storing the maize. The mortality of P. truncatus was four times higher in the trial where the fungi was applied as a preventive treatment. The mortality of S. zeamais was doubled in the treatment where the fungi was applied at the moment of inoculating with P. truncatus. Mortality levels caused by B. bassiana were higher in P. truncatus than in S. zeamais, but S. zeamais showed an infection 20% larger.