Suggested grasses for Montana
For general lawn use under moderate irrigation, sunlight and fertility levels
Kentucky Bluegrass (or one of its improved cultivars)
For semi-dryland lawns in eastern Montana, try sheep fescue or its subspecies, hard fescue, or the newer turf-type tall fescues. Because these differ in growth habit and texture, they are best planted alone rather than as a mix. Many are also clump-forming grasses and must be seeded thickly to form a decent lawn.
Under very dry conditions or in non-irrigated Montana lawns, Fairway crested wheatgrass, streambank wheatgrass, meadow bromegrass and smooth bromegrass are good choices. These will become brown during drought periods and should not be mowed to heights of less than three inches. Except for crested wheatgrass, all are rhizomatous (spreading laterally under the surface) and form a reasonably good sod. They all have similar characteristics and can be mixed. Buffalograss and blue grama grass will grow with little moisture and will form a sod that can be mown at about 2.5" in height.
Promoting healthy growth and avoiding conditions that cause stress to your turfgrass is the best way to prevent a severe disease outbreak. Stressed lawns are an open invitation for a lawn disease to gain a foothold. Optimal maintenance practices are the best way of avoiding stressed turfgrass.
Even if a pathogen is present in the soil, infection will not occur unless the environmental conditions are conducive to disease development. Once turf diseases have become active, they can cause heavy damage if not treated properly. Here is a list of common diseases to Montana lawns:
Professional Montana turfgrass associations: Association of Montana Turf, Ornamental & Pest Professionals, Northwest Turfgrass Association