Patch diseases can be very damaging to most cool-season turf grasses. These diseases cause circular patches of dead turf, which may surround turf that is still green. This "frog eye" symptom often occurs with this group of diseases.
Patch diseases generally occur on sodded lawns, especially within the first 5 years of establishment. However, older lawns either established from seed or sod can also develop patch diseases.
Several fungi cause patch diseases. The actual fungal pathogen will depend on the specific patch disease. The more commonly occurring patch disease includes the following: