Brown patch
Rhizoctonia solani
A fungal disease that causes circular brown patches, often with a darker "smoke ring" edge, in mild, humid weather in spring and autumn.
Also called: Large patch, Rhizoctonia
Short answer
Brown patch is a fungal lawn disease that causes roughly circular brown patches, often with a darker edge, in mild, humid weather in spring and autumn. Water early in the morning so leaves dry during the day, water deeply and less often, and improve drainage. If a fungicide is needed, use one whose label lists brown patch and your grass.
Overview
Brown patch is caused by the fungus Rhizoctonia solani. It shows up in mild, humid spells in spring and autumn as roughly circular brown patches, often with a darker “smoke ring” at the edge on dewy mornings.
Outbreaks are linked to conditions: mild, humid weather, leaves that stay wet for long periods, poor drainage or heavy thatch. Fixing those is the main cure. A fungicide whose label lists brown patch can help in a bad outbreak.
Symptoms
- Circular patches from about 5 cm up to a metre across
- A dark, smoky-looking ring at the edge of the patch, especially early in the morning
- Leaves that look water-soaked before turning dark brown
Conditions that bring it on
- Mild temperatures (around 15 to 20 °C) with high humidity
- Long periods of leaf wetness, such as heavy dew or evening watering
- Poor drainage and heavy thatch that keep the surface damp
When it's active
| Zone | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Subtropical | ● | ● | ● | ● | ● | ● | ||||||
| Warm temperate | ● | ● | ● | ● | ● | ● | ||||||
| Temperate | ● | ● | ● | ● | ● | ● |
Prevention
Water in the early morning so leaves dry during the day; avoid evening watering.
Water deeply and less often rather than a little every day.
Improve drainage and reduce thatch so the surface dries out.
Fungicide options
| Timing | Active ingredient | What it does | Grass types |
|---|---|---|---|
| curative | See product label | Fungicides registered for brown patch (Rhizoctonia) in turf. Check the label lists the disease and your grass type, and fix the conditions too. | Check the label |
In the Lawn Calendar
Roughly circular yellow or brown patches in mild, humid weather can be brown patch. Water in the morning so leaves dry during the day, and avoid overwatering.
March, April, May, September, October, November · Subtropical, Warm temperate, Temperate
Popular questions about brown patch
Guides
Common questions
Is brown patch caused by overwatering?
Overwatering doesn't cause it on its own, but leaves that stay wet, especially overnight, give the fungus the conditions it needs. Water early in the morning instead.
Didn't answer your question?
Ask LawnMan. We check existing answers first, and if nothing fits, your question goes on our list to answer.
Who wrote this, and what it's based on
This page hasn't been reviewed by our technical reviewer yet [CONFIRM: reviewer]. Until it is, it isn't listed in search engines. How we write and review
Sources
- Turf weed, pest and disease identification guide (poster), Bayer Environmental Science, hosted by Turf AustraliaBrown patch: smoke ring; water-soaked leaves turning dark brown; patches 5 cm to 1 m; 15 to 20 °C with high humidity, mainly spring and autumn. Accessed 3 October 2026.