I think because a susceptible turf doesn't get it because its simply susceptible. Certain environmental conditions or certain cultural practices cause fungus. Its not the result of a certain plant species.
Since fungus never seems to form in dry conditions. Over wet conditions such as a poorly drained area are prime for fungus vs an area of good drainage. Poor drainage could be a area that hasn't gotten water in several days but still remains saturated. This will set the stage for fungus first and foremost.
It's pretty obvious that poor draining areas greatly increase the chance of all fungus varieties regardless of the plant variety in the same location. Areas that drain well and dry well most likely won't have fungus because it can't ignite in dry conditions.
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