Abstract: The migratory grasshopper, Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae), is one of the most important grasshoppers in western North America rangelands in Fort Collins, CO (USA). The laboratory bioassay trials were conducted to determine the specific effect of microbial insecticides and repellents for control of migratory grasshopper in Fort Collins, Colorado. In an initial trial, both Beauveria bassiana and spinosad treated foliage produced significant mortality to grasshoppers at 120 h post-exposure, with some more rapid mortality within 24 h when spinosad was used at a higher rate. Significant mortality from B. bassiana was first observed after 72 h, with the high rate (1 lb/100 gal concentration). In a second trial treatment with Bioneem, Trilogy (neem oil), and Garlic Barrier were also included all treatments caused significant mortality at 96 h, with significantly most mortality with B. bassiana and spinosad. At 192 h, B. bassiana and spinosad produced 100% mortality. In conclusion, Beauveria bassiana and Spinosad were effective microbial insecticide for reducing population density of migratory grasshopper in both laboratory bioassays trials. In addition, Bioneem had significant repellent effects on migratory grasshoppers.