· Michael Blair
Warm nights and high humidity are what brown patch needs, and a Middle Tennessee July supplies both. On fescue it is the most common disease by a wide margin.
Recognising it
Roughly circular patches from a few inches to several feet, often with a darker smoke-coloured ring visible in early morning dew. Individual blades show tan lesions with a dark border.
It spreads while the surrounding lawn stays green, which distinguishes it from dormancy.
What feeds it
Leaf wetness overnight, high nitrogen going into summer, poor air movement, and thatch. Evening watering is the most controllable of those and the most common mistake.
Watering early so the blades dry as the day warms substantially reduces pressure.
- Water early morning, never evening
- No heavy nitrogen going into summer
- Raise mowing height and keep blades sharp
- Improve air movement where you can
- Fungicide is preventive rather than curative
Cultural control first
Correct watering timing, sensible mowing height, a sharp blade and avoiding summer nitrogen do most of the work. Torn blade tips from a dull mower are an entry point.
A lawn managed this way still gets brown patch in a bad year and gets it less and recovers faster.
Fungicides
They are preventive rather than curative — applied before or at the earliest signs, on a repeat interval through the pressure period.
For most home lawns the cultural approach plus accepting some summer damage is the reasonable position, since fescue recovers with autumn overseeding.